Code clean up: use range-style for loops wherever possible

Where not possible, use "auto" to get the iterator type.

Editorial note: I have avoid this change for a long time because of
not wanting to make gratuitous changes to version history, which can
obscure when certain changes were made, but with having recently
touched every single file to apply automatic code formatting and with
making several broad changes to the API, I decided it was time to take
the plunge and get rid of the older (pre-C++11) verbose iterator
syntax. The new code is just easier to read and understand, and in
many cases, it will be more effecient as fewer temporary copies are
being made.

m-holger, if you're reading, you can see that I've finally come
around. :-)

32 files changed, 367 insertions, 818 deletions

diff --git a/examples/pdf-filter-tokens.cc b/examples/pdf-filter-tokens.cc
index 59c85271..3d4bad8b 100644
--- a/examples/pdf-filter-tokens.cc
+++ b/examples/pdf-filter-tokens.cc
@@ -193,15 +193,12 @@ main(int argc, char* argv[])
         pdf.processFile(infilename);
         std::vector<QPDFPageObjectHelper> pages =
             QPDFPageDocumentHelper(pdf).getAllPages();
-        for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-             iter != pages.end();
-             ++iter) {
+        for (auto& page: pages) {
             // Attach two token filters to each page of this file.
             // When the file is written, or when the pages' contents
             // are retrieved in any other way, the filters will be
             // applied. See comments on the filters for additional
             // details.
-            QPDFPageObjectHelper& page(*iter);
             page.addContentTokenFilter(
                 std::shared_ptr<QPDFObjectHandle::TokenFilter>(
                     new StringReverser));
diff --git a/examples/pdf-invert-images.cc b/examples/pdf-invert-images.cc
index bd36f33f..b784c8e3 100644
--- a/examples/pdf-invert-images.cc
+++ b/examples/pdf-invert-images.cc
@@ -131,14 +131,11 @@ main(int argc, char* argv[])
         // For each page...
         std::vector<QPDFPageObjectHelper> pages =
             QPDFPageDocumentHelper(qpdf).getAllPages();
-        for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-             iter != pages.end();
-             ++iter) {
-            QPDFPageObjectHelper& page(*iter);
+        for (auto& page: pages) {
             // Get all images on the page.
             std::map<std::string, QPDFObjectHandle> images = page.getImages();
-            for (auto& iter2: images) {
-                QPDFObjectHandle& image = iter2.second;
+            for (auto& iter: images) {
+                QPDFObjectHandle& image = iter.second;
                 QPDFObjectHandle image_dict = image.getDict();
                 QPDFObjectHandle color_space = image_dict.getKey("/ColorSpace");
                 QPDFObjectHandle bits_per_component =
diff --git a/examples/pdf-mod-info.cc b/examples/pdf-mod-info.cc
index 425a25ba..2b8e3c47 100644
--- a/examples/pdf-mod-info.cc
+++ b/examples/pdf-mod-info.cc
@@ -132,10 +132,7 @@ main(int argc, char* argv[])
         QPDFObjectHandle filetrailer = file.getTrailer();
         QPDFObjectHandle fileinfo;
 
-        for (std::map<std::string, std::string>::const_iterator it =
-                 Keys.begin();
-             Keys.end() != it;
-             ++it) {
+        for (auto const& it: Keys) {
             if (!fileinfo.isInitialized()) {
                 if (filetrailer.hasKey("/Info")) {
                     QTC::TC("examples", "pdf-mod-info has info");
@@ -146,12 +143,12 @@ main(int argc, char* argv[])
                     filetrailer.replaceKey("/Info", fileinfo);
                 }
             }
-            if (it->second == "") {
-                fileinfo.removeKey(it->first);
+            if (it.second == "") {
+                fileinfo.removeKey(it.first);
             } else {
-                QPDFObjectHandle elt = fileinfo.newString(it->second);
+                QPDFObjectHandle elt = fileinfo.newString(it.second);
                 elt.makeDirect();
-                fileinfo.replaceKey(it->first, elt);
+                fileinfo.replaceKey(it.first, elt);
             }
         }
         QPDFWriter w(file, fl_tmp.c_str());
diff --git a/examples/pdf-overlay-page.cc b/examples/pdf-overlay-page.cc
index 64a8d48f..f9603d9c 100644
--- a/examples/pdf-overlay-page.cc
+++ b/examples/pdf-overlay-page.cc
@@ -42,11 +42,7 @@ stamp_page(char const* infile, char const* stampfile, char const* outfile)
     // For each page...
     std::vector<QPDFPageObjectHelper> pages =
         QPDFPageDocumentHelper(inpdf).getAllPages();
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter) {
-        QPDFPageObjectHelper& ph = *iter;
-
+    for (auto& ph: pages) {
         // Find a unique resource name for the new form XObject
         QPDFObjectHandle resources = ph.getAttribute("/Resources", true);
         int min_suffix = 1;
diff --git a/examples/pdf-set-form-values.cc b/examples/pdf-set-form-values.cc
index 10394c7b..c28149ad 100644
--- a/examples/pdf-set-form-values.cc
+++ b/examples/pdf-set-form-values.cc
@@ -52,23 +52,17 @@ main(int argc, char* argv[])
         QPDFAcroFormDocumentHelper afdh(qpdf);
         QPDFPageDocumentHelper pdh(qpdf);
         std::vector<QPDFPageObjectHelper> pages = pdh.getAllPages();
-        for (std::vector<QPDFPageObjectHelper>::iterator page_iter =
-                 pages.begin();
-             page_iter != pages.end();
-             ++page_iter) {
+        for (auto const& page: pages) {
             // Get all widget annotations for each page. Widget
             // annotations are the ones that contain the details of
             // what's in a form field.
             std::vector<QPDFAnnotationObjectHelper> annotations =
-                afdh.getWidgetAnnotationsForPage(*page_iter);
-            for (std::vector<QPDFAnnotationObjectHelper>::iterator annot_iter =
-                     annotations.begin();
-                 annot_iter != annotations.end();
-                 ++annot_iter) {
+                afdh.getWidgetAnnotationsForPage(page);
+            for (auto& annot: annotations) {
                 // For each annotation, find its associated field. If
                 // it's a text field, set its value.
                 QPDFFormFieldObjectHelper ffh =
-                    afdh.getFieldForAnnotation(*annot_iter);
+                    afdh.getFieldForAnnotation(annot);
                 if (ffh.getFieldType() == "/Tx") {
                     // Set the value. Passing false as the second
                     // value prevents qpdf from setting
@@ -81,7 +75,7 @@ main(int argc, char* argv[])
                     // additional details, please see comments in
                     // QPDFFormFieldObjectHelper.hh for this method.
                     ffh.setV(value, false);
-                    ffh.generateAppearance(*annot_iter);
+                    ffh.generateAppearance(annot);
                 }
             }
         }
diff --git a/examples/pdf-split-pages.cc b/examples/pdf-split-pages.cc
index a8e65260..150de0df 100644
--- a/examples/pdf-split-pages.cc
+++ b/examples/pdf-split-pages.cc
@@ -27,10 +27,7 @@ process(char const* whoami, char const* infile, std::string outprefix)
     int pageno_len =
         QIntC::to_int(QUtil::uint_to_string(pages.size()).length());
     int pageno = 0;
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter) {
-        QPDFPageObjectHelper& page(*iter);
+    for (auto& page: pages) {
         std::string outfile =
             outprefix + QUtil::int_to_string(++pageno, pageno_len) + ".pdf";
         QPDF outpdf;
diff --git a/fuzz/qpdf_fuzzer.cc b/fuzz/qpdf_fuzzer.cc
index aba08c7f..8b192b51 100644
--- a/fuzz/qpdf_fuzzer.cc
+++ b/fuzz/qpdf_fuzzer.cc
@@ -134,10 +134,7 @@ FuzzHelper::testPages()
     std::vector<QPDFPageObjectHelper> pages = pdh.getAllPages();
     DiscardContents discard_contents;
     int pageno = 0;
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter) {
-        QPDFPageObjectHelper& page(*iter);
+    for (auto& page: pages) {
         ++pageno;
         try {
             page.coalesceContentStreams();
@@ -150,11 +147,7 @@ FuzzHelper::testPages()
 
             std::vector<QPDFAnnotationObjectHelper> annotations =
                 afdh.getWidgetAnnotationsForPage(page);
-            for (std::vector<QPDFAnnotationObjectHelper>::iterator annot_iter =
-                     annotations.begin();
-                 annot_iter != annotations.end();
-                 ++annot_iter) {
-                QPDFAnnotationObjectHelper& aoh = *annot_iter;
+            for (auto& aoh: annotations) {
                 afdh.getFieldForAnnotation(aoh);
             }
         } catch (QPDFExc& e) {
@@ -172,11 +165,7 @@ FuzzHelper::testOutlines()
     queue.push_back(odh.getTopLevelOutlines());
     while (!queue.empty()) {
         std::vector<QPDFOutlineObjectHelper>& outlines = *(queue.begin());
-        for (std::vector<QPDFOutlineObjectHelper>::iterator iter =
-                 outlines.begin();
-             iter != outlines.end();
-             ++iter) {
-            QPDFOutlineObjectHelper& ol = *iter;
+        for (auto& ol: outlines) {
             ol.getDestPage();
             queue.push_back(ol.getKids());
         }
diff --git a/libqpdf/QPDF.cc b/libqpdf/QPDF.cc
index bab30042..815894d3 100644
--- a/libqpdf/QPDF.cc
+++ b/libqpdf/QPDF.cc
@@ -262,11 +262,8 @@ QPDF::~QPDF()
     // have the effect of undoing any modifications that may have been
     // made to any of the objects.
     this->m->xref_table.clear();
-    for (std::map<QPDFObjGen, ObjCache>::iterator iter =
-             this->m->obj_cache.begin();
-         iter != this->m->obj_cache.end();
-         ++iter) {
-        QPDFObject::ObjAccessor::releaseResolved((*iter).second.object.get());
+    for (auto const& iter: this->m->obj_cache) {
+        QPDFObject::ObjAccessor::releaseResolved(iter.second.object.get());
     }
 }
 
@@ -577,18 +574,13 @@ QPDF::reconstruct_xref(QPDFExc& e)
 
     // Delete all references to type 1 (uncompressed) objects
     std::set<QPDFObjGen> to_delete;
-    for (std::map<QPDFObjGen, QPDFXRefEntry>::iterator iter =
-             this->m->xref_table.begin();
-         iter != this->m->xref_table.end();
-         ++iter) {
-        if (((*iter).second).getType() == 1) {
-            to_delete.insert((*iter).first);
+    for (auto const& iter: this->m->xref_table) {
+        if (iter.second.getType() == 1) {
+            to_delete.insert(iter.first);
         }
     }
-    for (std::set<QPDFObjGen>::iterator iter = to_delete.begin();
-         iter != to_delete.end();
-         ++iter) {
-        this->m->xref_table.erase(*iter);
+    for (auto const& iter: to_delete) {
+        this->m->xref_table.erase(iter);
     }
 
     this->m->file->seek(0, SEEK_END);
@@ -1015,10 +1007,7 @@ QPDF::read_xrefTable(qpdf_offset_t xref_offset)
     }
 
     // Handle any deleted items now that we've read the /XRefStm.
-    for (std::vector<QPDFObjGen>::iterator iter = deleted_items.begin();
-         iter != deleted_items.end();
-         ++iter) {
-        QPDFObjGen& og = *iter;
+    for (auto const& og: deleted_items) {
         insertXrefEntry(og.getObj(), 0, 0, og.getGen());
     }
 
@@ -1351,12 +1340,9 @@ QPDF::insertXrefEntry(int obj, int f0, qpdf_offset_t f1, int f2, bool overwrite)
 void
 QPDF::showXRefTable()
 {
-    for (std::map<QPDFObjGen, QPDFXRefEntry>::iterator iter =
-             this->m->xref_table.begin();
-         iter != this->m->xref_table.end();
-         ++iter) {
-        QPDFObjGen const& og = (*iter).first;
-        QPDFXRefEntry const& entry = (*iter).second;
+    for (auto const& iter: this->m->xref_table) {
+        QPDFObjGen const& og = iter.first;
+        QPDFXRefEntry const& entry = iter.second;
         *this->m->out_stream << og.getObj() << "/" << og.getGen() << ": ";
         switch (entry.getType()) {
         case 1:
@@ -1390,27 +1376,19 @@ QPDF::fixDanglingReferences(bool force)
     // Create a set of all known indirect objects including those
     // we've previously resolved and those that we have created.
     std::set<QPDFObjGen> to_process;
-    for (std::map<QPDFObjGen, ObjCache>::iterator iter =
-             this->m->obj_cache.begin();
-         iter != this->m->obj_cache.end();
-         ++iter) {
-        to_process.insert((*iter).first);
+    for (auto const& iter: this->m->obj_cache) {
+        to_process.insert(iter.first);
     }
-    for (std::map<QPDFObjGen, QPDFXRefEntry>::iterator iter =
-             this->m->xref_table.begin();
-         iter != this->m->xref_table.end();
-         ++iter) {
-        to_process.insert((*iter).first);
+    for (auto const& iter: this->m->xref_table) {
+        to_process.insert(iter.first);
     }
 
     // For each non-scalar item to process, put it in the queue.
     std::list<QPDFObjectHandle> queue;
     queue.push_back(this->m->trailer);
-    for (std::set<QPDFObjGen>::iterator iter = to_process.begin();
-         iter != to_process.end();
-         ++iter) {
+    for (auto const& iter: to_process) {
         QPDFObjectHandle obj = QPDFObjectHandle::Factory::newIndirect(
-            this, (*iter).getObj(), (*iter).getGen());
+            this, iter.getObj(), iter.getGen());
         if (obj.isDictionary() || obj.isArray()) {
             queue.push_back(obj);
         } else if (obj.isStream()) {
@@ -1428,21 +1406,15 @@ QPDF::fixDanglingReferences(bool force)
         if (obj.isDictionary()) {
             std::map<std::string, QPDFObjectHandle> members =
                 obj.getDictAsMap();
-            for (std::map<std::string, QPDFObjectHandle>::iterator iter =
-                     members.begin();
-                 iter != members.end();
-                 ++iter) {
-                to_check.push_back((*iter).second);
+            for (auto const& iter: members) {
+                to_check.push_back(iter.second);
             }
         } else if (obj.isArray()) {
             QPDF_Array* arr = dynamic_cast<QPDF_Array*>(
                 QPDFObjectHandle::ObjAccessor::getObject(obj).get());
             arr->addExplicitElementsToList(to_check);
         }
-        for (std::list<QPDFObjectHandle>::iterator iter = to_check.begin();
-             iter != to_check.end();
-             ++iter) {
-            QPDFObjectHandle sub = *iter;
+        for (auto sub: to_check) {
             if (sub.isIndirect()) {
                 if (sub.getOwningQPDF() == this) {
                     QPDFObjGen og(sub.getObjGen());
@@ -1480,11 +1452,8 @@ QPDF::getAllObjects()
     // object cache.
     fixDanglingReferences(true);
     std::vector<QPDFObjectHandle> result;
-    for (std::map<QPDFObjGen, ObjCache>::iterator iter =
-             this->m->obj_cache.begin();
-         iter != this->m->obj_cache.end();
-         ++iter) {
-        QPDFObjGen const& og = (*iter).first;
+    for (auto const& iter: this->m->obj_cache) {
+        QPDFObjGen const& og = iter.first;
         result.push_back(
             // line-break
             QPDFObjectHandle::Factory::newIndirect(
@@ -1733,12 +1702,9 @@ QPDF::recoverStreamLength(
         QPDFObjGen this_obj(0, 0);
 
         // Make sure this is inside this object
-        for (std::map<QPDFObjGen, QPDFXRefEntry>::iterator iter =
-                 this->m->xref_table.begin();
-             iter != this->m->xref_table.end();
-             ++iter) {
-            QPDFObjGen const& og = (*iter).first;
-            QPDFXRefEntry const& entry = (*iter).second;
+        for (auto const& iter: this->m->xref_table) {
+            QPDFObjGen const& og = iter.first;
+            QPDFXRefEntry const& entry = iter.second;
             if (entry.getType() == 1) {
                 qpdf_offset_t obj_offset = entry.getOffset();
                 if ((obj_offset > stream_offset) &&
@@ -2157,15 +2123,13 @@ QPDF::resolveObjectsInStream(int obj_stream_number)
     // that some objects stored here might have been overridden by new
     // objects appended to the file, so it is necessary to recheck the
     // xref table and only cache what would actually be resolved here.
-    for (std::map<int, int>::iterator iter = offsets.begin();
-         iter != offsets.end();
-         ++iter) {
-        int obj = (*iter).first;
+    for (auto const& iter: offsets) {
+        int obj = iter.first;
         QPDFObjGen og(obj, 0);
         QPDFXRefEntry const& entry = this->m->xref_table[og];
         if ((entry.getType() == 2) &&
             (entry.getObjStreamNumber() == obj_stream_number)) {
-            int offset = (*iter).second;
+            int offset = iter.second;
             input->seek(offset, SEEK_SET);
             QPDFObjectHandle oh = readObject(input, "", obj, 0, true);
             this->m->obj_cache[og] = ObjCache(
@@ -2317,11 +2281,7 @@ QPDF::copyForeignObject(QPDFObjectHandle foreign)
     }
 
     // Copy any new objects and replace the reservations.
-    for (std::vector<QPDFObjectHandle>::iterator iter =
-             obj_copier.to_copy.begin();
-         iter != obj_copier.to_copy.end();
-         ++iter) {
-        QPDFObjectHandle& to_copy = *iter;
+    for (auto& to_copy: obj_copier.to_copy) {
         QPDFObjectHandle copy =
             replaceForeignIndirectObjects(to_copy, obj_copier, true);
         if (!to_copy.isStream()) {
@@ -2365,8 +2325,7 @@ QPDF::reserveObjects(QPDFObjectHandle foreign, ObjCopier& obj_copier, bool top)
         }
         QTC::TC("qpdf", "QPDF copy indirect");
         obj_copier.visiting.insert(foreign_og);
-        std::map<QPDFObjGen, QPDFObjectHandle>::iterator mapping =
-            obj_copier.object_map.find(foreign_og);
+        auto mapping = obj_copier.object_map.find(foreign_og);
         if (mapping == obj_copier.object_map.end()) {
             obj_copier.to_copy.push_back(foreign);
             QPDFObjectHandle reservation;
@@ -2388,10 +2347,8 @@ QPDF::reserveObjects(QPDFObjectHandle foreign, ObjCopier& obj_copier, bool top)
     } else if (foreign.isDictionary()) {
         QTC::TC("qpdf", "QPDF reserve dictionary");
         std::set<std::string> keys = foreign.getKeys();
-        for (std::set<std::string>::iterator iter = keys.begin();
-             iter != keys.end();
-             ++iter) {
-            reserveObjects(foreign.getKey(*iter), obj_copier, false);
+        for (auto const& key: keys) {
+            reserveObjects(foreign.getKey(key), obj_copier, false);
         }
     } else if (foreign.isStream()) {
         QTC::TC("qpdf", "QPDF reserve stream");
@@ -2412,8 +2369,7 @@ QPDF::replaceForeignIndirectObjects(
     if ((!top) && foreign.isIndirect()) {
         QTC::TC("qpdf", "QPDF replace indirect");
         QPDFObjGen foreign_og(foreign.getObjGen());
-        std::map<QPDFObjGen, QPDFObjectHandle>::iterator mapping =
-            obj_copier.object_map.find(foreign_og);
+        auto mapping = obj_copier.object_map.find(foreign_og);
         if (mapping == obj_copier.object_map.end()) {
             // This case would occur if this is a reference to a Page
             // or Pages object that we didn't traverse into.
@@ -2657,12 +2613,9 @@ QPDF::getXRefTable()
 void
 QPDF::getObjectStreamData(std::map<int, int>& omap)
 {
-    for (std::map<QPDFObjGen, QPDFXRefEntry>::iterator iter =
-             this->m->xref_table.begin();
-         iter != this->m->xref_table.end();
-         ++iter) {
-        QPDFObjGen const& og = (*iter).first;
-        QPDFXRefEntry const& entry = (*iter).second;
+    for (auto const& iter: this->m->xref_table) {
+        QPDFObjGen const& og = iter.first;
+        QPDFXRefEntry const& entry = iter.second;
         if (entry.getType() == 2) {
             omap[og.getObj()] = entry.getObjStreamNumber();
         }
diff --git a/libqpdf/QPDFAcroFormDocumentHelper.cc b/libqpdf/QPDFAcroFormDocumentHelper.cc
index 435c7666..4e9f08b9 100644
--- a/libqpdf/QPDFAcroFormDocumentHelper.cc
+++ b/libqpdf/QPDFAcroFormDocumentHelper.cc
@@ -182,11 +182,8 @@ QPDFAcroFormDocumentHelper::getFormFields()
 {
     analyze();
     std::vector<QPDFFormFieldObjectHelper> result;
-    for (std::map<QPDFObjGen, std::vector<QPDFAnnotationObjectHelper>>::iterator
-             iter = this->m->field_to_annotations.begin();
-         iter != this->m->field_to_annotations.end();
-         ++iter) {
-        result.push_back(this->qpdf.getObjectByObjGen((*iter).first));
+    for (auto const& iter: this->m->field_to_annotations) {
+        result.push_back(this->qpdf.getObjectByObjGen(iter.first));
     }
     return result;
 }
@@ -299,17 +296,11 @@ QPDFAcroFormDocumentHelper::analyze()
 
     QPDFPageDocumentHelper dh(this->qpdf);
     std::vector<QPDFPageObjectHelper> pages = dh.getAllPages();
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter) {
-        QPDFPageObjectHelper ph(*iter);
+    for (auto const& ph: pages) {
         std::vector<QPDFAnnotationObjectHelper> annots =
             getWidgetAnnotationsForPage(ph);
-        for (std::vector<QPDFAnnotationObjectHelper>::iterator i2 =
-                 annots.begin();
-             i2 != annots.end();
-             ++i2) {
-            QPDFObjectHandle annot((*i2).getObjectHandle());
+        for (auto const& iter: annots) {
+            QPDFObjectHandle annot(iter.getObjectHandle());
             QPDFObjGen og(annot.getObjGen());
             if (this->m->annotation_to_field.count(og) == 0) {
                 QTC::TC("qpdf", "QPDFAcroFormDocumentHelper orphaned widget");
@@ -462,16 +453,10 @@ QPDFAcroFormDocumentHelper::generateAppearancesIfNeeded()
 
     QPDFPageDocumentHelper pdh(this->qpdf);
     std::vector<QPDFPageObjectHelper> pages = pdh.getAllPages();
-    for (std::vector<QPDFPageObjectHelper>::iterator page_iter = pages.begin();
-         page_iter != pages.end();
-         ++page_iter) {
+    for (auto const& page: pages) {
         std::vector<QPDFAnnotationObjectHelper> annotations =
-            getWidgetAnnotationsForPage(*page_iter);
-        for (std::vector<QPDFAnnotationObjectHelper>::iterator annot_iter =
-                 annotations.begin();
-             annot_iter != annotations.end();
-             ++annot_iter) {
-            QPDFAnnotationObjectHelper& aoh = *annot_iter;
+            getWidgetAnnotationsForPage(page);
+        for (auto& aoh: annotations) {
             QPDFFormFieldObjectHelper ffh = getFieldForAnnotation(aoh);
             if (ffh.getFieldType() == "/Btn") {
                 // Rather than generating appearances for button
diff --git a/libqpdf/QPDFArgParser.cc b/libqpdf/QPDFArgParser.cc
index 8cd53efa..63197684 100644
--- a/libqpdf/QPDFArgParser.cc
+++ b/libqpdf/QPDFArgParser.cc
@@ -294,10 +294,7 @@ QPDFArgParser::handleBashArguments()
     bool last_was_backslash = false;
     enum { st_top, st_squote, st_dquote } state = st_top;
     std::string arg;
-    for (std::string::iterator iter = this->m->bash_line.begin();
-         iter != this->m->bash_line.end();
-         ++iter) {
-        char ch = (*iter);
+    for (char ch: this->m->bash_line) {
         if (last_was_backslash) {
             arg.append(1, ch);
             last_was_backslash = false;
@@ -560,13 +557,14 @@ QPDFArgParser::parseArgs()
             } else if (!oe.choices.empty()) {
                 QTC::TC("libtests", "QPDFArgParser required choices");
                 message += "{";
-                for (std::set<std::string>::iterator iter = oe.choices.begin();
-                     iter != oe.choices.end();
-                     ++iter) {
-                    if (iter != oe.choices.begin()) {
+                bool first = true;
+                for (auto const& choice: oe.choices) {
+                    if (first) {
+                        first = false;
+                    } else {
                         message += ",";
                     }
-                    message += *iter;
+                    message += choice;
                 }
                 message += "}";
             } else if (!oe.parameter_name.empty()) {
@@ -624,11 +622,9 @@ QPDFArgParser::addChoicesToCompletions(
 {
     if (option_table.count(option) != 0) {
         OptionEntry& oe = option_table[option];
-        for (std::set<std::string>::iterator iter = oe.choices.begin();
-             iter != oe.choices.end();
-             ++iter) {
+        for (auto const& choice: oe.choices) {
             QTC::TC("libtests", "QPDFArgParser complete choices");
-            this->m->completions.insert(extra_prefix + *iter);
+            this->m->completions.insert(extra_prefix + choice);
         }
     }
 }
@@ -714,11 +710,9 @@ QPDFArgParser::handleCompletion()
         }
     }
     std::string prefix = extra_prefix + this->m->bash_cur;
-    for (std::set<std::string>::iterator iter = this->m->completions.begin();
-         iter != this->m->completions.end();
-         ++iter) {
-        if (prefix.empty() || ((*iter).substr(0, prefix.length()) == prefix)) {
-            std::cout << *iter << std::endl;
+    for (auto const& iter: this->m->completions) {
+        if (prefix.empty() || (iter.substr(0, prefix.length()) == prefix)) {
+            std::cout << iter << std::endl;
         }
     }
     exit(0);
diff --git a/libqpdf/QPDFJob.cc b/libqpdf/QPDFJob.cc
index e0cc783f..4d136223 100644
--- a/libqpdf/QPDFJob.cc
+++ b/libqpdf/QPDFJob.cc
@@ -852,10 +852,7 @@ QPDFJob::doCheck(QPDF& pdf)
         std::vector<QPDFPageObjectHelper> pages = dh.getAllPages();
         DiscardContents discard_contents;
         int pageno = 0;
-        for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-             iter != pages.end();
-             ++iter) {
-            QPDFPageObjectHelper& page(*iter);
+        for (auto& page: pages) {
             ++pageno;
             try {
                 page.parseContents(&discard_contents);
@@ -927,10 +924,7 @@ QPDFJob::doShowPages(QPDF& pdf)
     std::vector<QPDFPageObjectHelper> pages = dh.getAllPages();
     int pageno = 0;
     auto& cout = *this->m->cout;
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter) {
-        QPDFPageObjectHelper& ph(*iter);
+    for (auto& ph: pages) {
         QPDFObjectHandle page = ph.getObjectHandle();
         ++pageno;
 
@@ -1058,12 +1052,9 @@ QPDFJob::doJSONObjects(QPDF& pdf, JSON& j)
             "trailer", pdf.getTrailer().getJSON(true));
     }
     std::vector<QPDFObjectHandle> objects = pdf.getAllObjects();
-    for (std::vector<QPDFObjectHandle>::iterator iter = objects.begin();
-         iter != objects.end();
-         ++iter) {
-        if (all_objects || wanted_og.count((*iter).getObjGen())) {
-            j_objects.addDictionaryMember(
-                (*iter).unparse(), (*iter).getJSON(true));
+    for (auto& obj: objects) {
+        if (all_objects || wanted_og.count(obj.getObjGen())) {
+            j_objects.addDictionaryMember(obj.unparse(), obj.getJSON(true));
         }
     }
 }
@@ -1106,12 +1097,10 @@ QPDFJob::doJSONPages(QPDF& pdf, JSON& j)
     QPDFOutlineDocumentHelper odh(pdf);
     pdh.pushInheritedAttributesToPage();
     std::vector<QPDFPageObjectHelper> pages = pdh.getAllPages();
-    int pageno = 0;
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter, ++pageno) {
+    int pageno = -1;
+    for (auto& ph: pages) {
+        ++pageno;
         JSON j_page = j_pages.addArrayElement(JSON::makeDictionary());
-        QPDFPageObjectHelper& ph(*iter);
         QPDFObjectHandle page = ph.getObjectHandle();
         j_page.addDictionaryMember("object", page.getJSON());
         JSON j_images = j_page.addDictionaryMember("images", JSON::makeArray());
@@ -1161,17 +1150,14 @@ QPDFJob::doJSONPages(QPDF& pdf, JSON& j)
             j_page.addDictionaryMember("outlines", JSON::makeArray());
         std::vector<QPDFOutlineObjectHelper> outlines =
             odh.getOutlinesForPage(page.getObjGen());
-        for (std::vector<QPDFOutlineObjectHelper>::iterator oiter =
-                 outlines.begin();
-             oiter != outlines.end();
-             ++oiter) {
+        for (auto& oiter: outlines) {
             JSON j_outline = j_outlines.addArrayElement(JSON::makeDictionary());
             j_outline.addDictionaryMember(
-                "object", (*oiter).getObjectHandle().getJSON());
+                "object", oiter.getObjectHandle().getJSON());
             j_outline.addDictionaryMember(
-                "title", JSON::makeString((*oiter).getTitle()));
+                "title", JSON::makeString(oiter.getTitle()));
             j_outline.addDictionaryMember(
-                "dest", (*oiter).getDest().getJSON(true));
+                "dest", oiter.getDest().getJSON(true));
         }
         j_page.addDictionaryMember("pageposfrom1", JSON::makeInt(1 + pageno));
     }
@@ -1188,10 +1174,8 @@ QPDFJob::doJSONPageLabels(QPDF& pdf, JSON& j)
         std::vector<QPDFObjectHandle> labels;
         pldh.getLabelsForPageRange(
             0, QIntC::to_int(pages.size()) - 1, 0, labels);
-        for (std::vector<QPDFObjectHandle>::iterator iter = labels.begin();
-             iter != labels.end();
-             ++iter) {
-            std::vector<QPDFObjectHandle>::iterator next = iter;
+        for (auto iter = labels.begin(); iter != labels.end(); ++iter) {
+            auto next = iter;
             ++next;
             if (next == labels.end()) {
                 // This can't happen, so ignore it. This could only
@@ -1213,10 +1197,7 @@ add_outlines_to_json(
     JSON& j,
     std::map<QPDFObjGen, int>& page_numbers)
 {
-    for (std::vector<QPDFOutlineObjectHelper>::iterator iter = outlines.begin();
-         iter != outlines.end();
-         ++iter) {
-        QPDFOutlineObjectHelper& ol = *iter;
+    for (auto& ol: outlines) {
         JSON jo = j.addArrayElement(JSON::makeDictionary());
         jo.addDictionaryMember("object", ol.getObjectHandle().getJSON());
         jo.addDictionaryMember("title", JSON::makeString(ol.getTitle()));
@@ -1243,10 +1224,8 @@ QPDFJob::doJSONOutlines(QPDF& pdf, JSON& j)
     QPDFPageDocumentHelper dh(pdf);
     std::vector<QPDFPageObjectHelper> pages = dh.getAllPages();
     int n = 0;
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter) {
-        QPDFObjectHandle oh = (*iter).getObjectHandle();
+    for (auto const& ph: pages) {
+        QPDFObjectHandle oh = ph.getObjectHandle();
         page_numbers[oh.getObjGen()] = ++n;
     }
 
@@ -1268,17 +1247,11 @@ QPDFJob::doJSONAcroform(QPDF& pdf, JSON& j)
     QPDFPageDocumentHelper pdh(pdf);
     std::vector<QPDFPageObjectHelper> pages = pdh.getAllPages();
     int pagepos1 = 0;
-    for (std::vector<QPDFPageObjectHelper>::iterator page_iter = pages.begin();
-         page_iter != pages.end();
-         ++page_iter) {
+    for (auto const& page: pages) {
         ++pagepos1;
         std::vector<QPDFAnnotationObjectHelper> annotations =
-            afdh.getWidgetAnnotationsForPage(*page_iter);
-        for (std::vector<QPDFAnnotationObjectHelper>::iterator annot_iter =
-                 annotations.begin();
-             annot_iter != annotations.end();
-             ++annot_iter) {
-            QPDFAnnotationObjectHelper& aoh = *annot_iter;
+            afdh.getWidgetAnnotationsForPage(page);
+        for (auto& aoh: annotations) {
             QPDFFormFieldObjectHelper ffh = afdh.getFieldForAnnotation(aoh);
             JSON j_field = j_fields.addArrayElement(JSON::makeDictionary());
             j_field.addDictionaryMember(
@@ -1314,10 +1287,8 @@ QPDFJob::doJSONAcroform(QPDF& pdf, JSON& j)
             JSON j_choices =
                 j_field.addDictionaryMember("choices", JSON::makeArray());
             std::vector<std::string> choices = ffh.getChoices();
-            for (std::vector<std::string>::iterator iter = choices.begin();
-                 iter != choices.end();
-                 ++iter) {
-                j_choices.addArrayElement(JSON::makeString(*iter));
+            for (auto const& choice: choices) {
+                j_choices.addArrayElement(JSON::makeString(choice));
             }
             JSON j_annot = j_field.addDictionaryMember(
                 "annotation", JSON::makeDictionary());
@@ -1688,10 +1659,8 @@ Please report this as a bug at\n\
    https://github.com/qpdf/qpdf/issues/new\n\
 ideally with the file that caused the error and the output below. Thanks!\n\
 \n";
-        for (std::list<std::string>::iterator iter = errors.begin();
-             iter != errors.end();
-             ++iter) {
-            *(this->m->cerr) << (*iter) << std::endl;
+        for (auto const& error: errors) {
+            *(this->m->cerr) << error << std::endl;
         }
     }
 
@@ -1816,10 +1785,8 @@ QPDFJob::doProcess(
         QUtil::possible_repaired_encodings(password);
     // Represent to char const*, as required by the QPDF class.
     std::vector<char const*> passwords;
-    for (std::vector<std::string>::iterator iter = passwords_str.begin();
-         iter != passwords_str.end();
-         ++iter) {
-        passwords.push_back((*iter).c_str());
+    for (auto const& iter: passwords_str) {
+        passwords.push_back(iter.c_str());
     }
     // We always try the supplied password first because it is the
     // first string returned by possible_repaired_encodings. If there
@@ -1835,13 +1802,11 @@ QPDFJob::doProcess(
     // attempt, which, like the first attempt, will be with the
     // supplied password.
     bool warned = false;
-    for (std::vector<char const*>::iterator iter = passwords.begin();
-         iter != passwords.end();
-         ++iter) {
+    for (auto iter = passwords.begin(); iter != passwords.end(); ++iter) {
         try {
             return doProcessOnce(fn, *iter, empty, used_for_input);
         } catch (QPDFExc& e) {
-            std::vector<char const*>::iterator next = iter;
+            auto next = iter;
             ++next;
             if (next == passwords.end()) {
                 throw e;
@@ -1961,10 +1926,7 @@ QPDFJob::doUnderOverlayForPage(
         resources = dest_page.getObjectHandle().replaceKeyAndGet(
             "/Resources", QPDFObjectHandle::newDictionary());
     }
-    for (std::vector<int>::iterator iter = pagenos[pageno].begin();
-         iter != pagenos[pageno].end();
-         ++iter) {
-        int from_pageno = *iter;
+    for (int from_pageno: pagenos[pageno]) {
         doIfVerbose([&](std::ostream& cout, std::string const& prefix) {
             cout << "    " << uo.which << " " << from_pageno << std::endl;
         });
@@ -2017,15 +1979,14 @@ QPDFJob::getUOPagenos(
     size_t idx = 0;
     size_t from_size = uo.from_pagenos.size();
     size_t repeat_size = uo.repeat_pagenos.size();
-    for (std::vector<int>::iterator iter = uo.to_pagenos.begin();
-         iter != uo.to_pagenos.end();
-         ++iter, ++idx) {
+    for (int to_pageno: uo.to_pagenos) {
         if (idx < from_size) {
-            pagenos[*iter].push_back(uo.from_pagenos.at(idx));
+            pagenos[to_pageno].push_back(uo.from_pagenos.at(idx));
         } else if (repeat_size) {
-            pagenos[*iter].push_back(
+            pagenos[to_pageno].push_back(
                 uo.repeat_pagenos.at((idx - from_size) % repeat_size));
         }
+        ++idx;
     }
 }
 
@@ -2206,21 +2167,15 @@ QPDFJob::handleTransformations(QPDF& pdf)
     if (m->externalize_inline_images ||
         (m->optimize_images && (!m->keep_inline_images))) {
         std::vector<QPDFPageObjectHelper> pages = dh.getAllPages();
-        for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-             iter != pages.end();
-             ++iter) {
-            QPDFPageObjectHelper& ph(*iter);
+        for (auto& ph: pages) {
             ph.externalizeInlineImages(m->ii_min_bytes);
         }
     }
     if (m->optimize_images) {
         int pageno = 0;
         std::vector<QPDFPageObjectHelper> pages = dh.getAllPages();
-        for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-             iter != pages.end();
-             ++iter) {
+        for (auto& ph: pages) {
             ++pageno;
-            QPDFPageObjectHelper& ph(*iter);
             QPDFObjectHandle page = ph.getObjectHandle();
             std::map<std::string, QPDFObjectHandle> images = ph.getImages();
             for (auto& iter2: images) {
@@ -2260,10 +2215,8 @@ QPDFJob::handleTransformations(QPDF& pdf)
     }
     if (m->coalesce_contents) {
         std::vector<QPDFPageObjectHelper> pages = dh.getAllPages();
-        for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-             iter != pages.end();
-             ++iter) {
-            (*iter).coalesceContentStreams();
+        for (auto& page: pages) {
+            page.coalesceContentStreams();
         }
     }
     if (m->flatten_rotation) {
@@ -2428,10 +2381,7 @@ QPDFJob::handlePageSpecs(
     // actual pages.
 
     // Handle "." as a shortcut for the input file
-    for (std::vector<QPDFJob::PageSpec>::iterator iter = m->page_specs.begin();
-         iter != m->page_specs.end();
-         ++iter) {
-        QPDFJob::PageSpec& page_spec = *iter;
+    for (auto& page_spec: m->page_specs) {
         if (page_spec.filename == ".") {
             page_spec.filename = m->infilename.get();
         }
@@ -2463,10 +2413,7 @@ QPDFJob::handlePageSpecs(
     page_spec_qpdfs[m->infilename.get()] = &pdf;
     std::vector<QPDFPageData> parsed_specs;
     std::map<unsigned long long, std::set<QPDFObjGen>> copied_pages;
-    for (std::vector<QPDFJob::PageSpec>::iterator iter = m->page_specs.begin();
-         iter != m->page_specs.end();
-         ++iter) {
-        QPDFJob::PageSpec& page_spec = *iter;
+    for (auto& page_spec: m->page_specs) {
         if (page_spec_qpdfs.count(page_spec.filename) == 0) {
             // Open the PDF file and store the QPDF object. Throw a
             // std::shared_ptr to the qpdf into a heap so that it
@@ -2523,17 +2470,14 @@ QPDFJob::handlePageSpecs(
 
     std::map<unsigned long long, bool> remove_unreferenced;
     if (m->remove_unreferenced_page_resources != QPDFJob::re_no) {
-        for (std::map<std::string, QPDF*>::iterator iter =
-                 page_spec_qpdfs.begin();
-             iter != page_spec_qpdfs.end();
-             ++iter) {
-            std::string const& filename = (*iter).first;
+        for (auto const& iter: page_spec_qpdfs) {
+            std::string const& filename = iter.first;
             ClosedFileInputSource* cis = 0;
             if (page_spec_cfis.count(filename)) {
                 cis = page_spec_cfis[filename];
                 cis->stayOpen(true);
             }
-            QPDF& other(*((*iter).second));
+            QPDF& other(*(iter.second));
             auto other_uuid = other.getUniqueId();
             if (remove_unreferenced.count(other_uuid) == 0) {
                 remove_unreferenced[other_uuid] =
@@ -2556,10 +2500,8 @@ QPDFJob::handlePageSpecs(
     });
     QPDFPageDocumentHelper dh(pdf);
     std::vector<QPDFPageObjectHelper> orig_pages = dh.getAllPages();
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = orig_pages.begin();
-         iter != orig_pages.end();
-         ++iter) {
-        dh.removePage(*iter);
+    for (auto const& page: orig_pages) {
+        dh.removePage(page);
     }
 
     if (m->collate && (parsed_specs.size() > 1)) {
@@ -2601,10 +2543,7 @@ QPDFJob::handlePageSpecs(
         afdh_map;
     auto this_afdh = get_afdh_for_qpdf(afdh_map, &pdf);
     std::set<QPDFObjGen> referenced_fields;
-    for (std::vector<QPDFPageData>::iterator iter = parsed_specs.begin();
-         iter != parsed_specs.end();
-         ++iter) {
-        QPDFPageData& page_data = *iter;
+    for (auto& page_data: parsed_specs) {
         ClosedFileInputSource* cis = 0;
         if (page_spec_cfis.count(page_data.filename)) {
             cis = page_spec_cfis[page_data.filename];
@@ -2619,14 +2558,12 @@ QPDFJob::handlePageSpecs(
             cout << prefix << ": adding pages from " << page_data.filename
                  << std::endl;
         });
-        for (std::vector<int>::iterator pageno_iter =
-                 page_data.selected_pages.begin();
-             pageno_iter != page_data.selected_pages.end();
-             ++pageno_iter, ++out_pageno) {
+        for (auto pageno_iter: page_data.selected_pages) {
             // Pages are specified from 1 but numbered from 0 in the
             // vector
-            int pageno = *pageno_iter - 1;
-            pldh.getLabelsForPageRange(pageno, pageno, out_pageno, new_labels);
+            int pageno = pageno_iter - 1;
+            pldh.getLabelsForPageRange(
+                pageno, pageno, out_pageno++, new_labels);
             QPDFPageObjectHelper to_copy =
                 page_data.orig_pages.at(QIntC::to_size(pageno));
             QPDFObjGen to_copy_og = to_copy.getObjectHandle().getObjGen();
@@ -2748,19 +2685,14 @@ QPDFJob::handleRotations(QPDF& pdf)
     QPDFPageDocumentHelper dh(pdf);
     std::vector<QPDFPageObjectHelper> pages = dh.getAllPages();
     int npages = QIntC::to_int(pages.size());
-    for (std::map<std::string, QPDFJob::RotationSpec>::iterator iter =
-             m->rotations.begin();
-         iter != m->rotations.end();
-         ++iter) {
-        std::string const& range = (*iter).first;
-        QPDFJob::RotationSpec const& rspec = (*iter).second;
+    for (auto const& iter: m->rotations) {
+        std::string const& range = iter.first;
+        QPDFJob::RotationSpec const& rspec = iter.second;
         // range has been previously validated
         std::vector<int> to_rotate =
             QUtil::parse_numrange(range.c_str(), npages);
-        for (std::vector<int>::iterator i2 = to_rotate.begin();
-             i2 != to_rotate.end();
-             ++i2) {
-            int pageno = *i2 - 1;
+        for (int pageno_iter: to_rotate) {
+            int pageno = pageno_iter - 1;
             if ((pageno >= 0) && (pageno < npages)) {
                 pages.at(QIntC::to_size(pageno))
                     .rotatePage(rspec.angle, rspec.relative);
diff --git a/libqpdf/QPDFObjectHandle.cc b/libqpdf/QPDFObjectHandle.cc
index c156e627..76a6127e 100644
--- a/libqpdf/QPDFObjectHandle.cc
+++ b/libqpdf/QPDFObjectHandle.cc
@@ -1244,17 +1244,12 @@ QPDFObjectHandle::getResourceNames()
         return result;
     }
     std::set<std::string> keys = getKeys();
-    for (std::set<std::string>::iterator iter = keys.begin();
-         iter != keys.end();
-         ++iter) {
-        std::string const& key = *iter;
+    for (auto const& key: keys) {
         QPDFObjectHandle val = getKey(key);
         if (val.isDictionary()) {
             std::set<std::string> val_keys = val.getKeys();
-            for (std::set<std::string>::iterator i2 = val_keys.begin();
-                 i2 != val_keys.end();
-                 ++i2) {
-                result.insert(*i2);
+            for (auto const& val_key: val_keys) {
+                result.insert(val_key);
             }
         }
     }
@@ -1620,10 +1615,7 @@ QPDFObjectHandle::arrayOrStreamToStreamArray(
     }
 
     bool first = true;
-    for (std::vector<QPDFObjectHandle>::iterator iter = result.begin();
-         iter != result.end();
-         ++iter) {
-        QPDFObjectHandle item = *iter;
+    for (auto const& item: result) {
         std::string og = QUtil::int_to_string(item.getObjectID()) + " " +
             QUtil::int_to_string(item.getGeneration());
         if (first) {
@@ -1660,11 +1652,9 @@ QPDFObjectHandle::addPageContents(QPDFObjectHandle new_contents, bool first)
         QTC::TC("qpdf", "QPDFObjectHandle prepend page contents");
         content_streams.push_back(new_contents);
     }
-    for (std::vector<QPDFObjectHandle>::iterator iter = orig_contents.begin();
-         iter != orig_contents.end();
-         ++iter) {
+    for (auto const& iter: orig_contents) {
         QTC::TC("qpdf", "QPDFObjectHandle append page contents");
-        content_streams.push_back(*iter);
+        content_streams.push_back(iter);
     }
     if (!first) {
         content_streams.push_back(new_contents);
@@ -1865,14 +1855,11 @@ QPDFObjectHandle::pipeContentStreams(
         arrayOrStreamToStreamArray(description, all_description);
     bool need_newline = false;
     Pl_Buffer buf("concatenated content stream buffer");
-    for (std::vector<QPDFObjectHandle>::iterator iter = streams.begin();
-         iter != streams.end();
-         ++iter) {
+    for (auto stream: streams) {
         if (need_newline) {
             buf.write(QUtil::unsigned_char_pointer("\n"), 1);
         }
         LastChar lc(&buf);
-        QPDFObjectHandle stream = *iter;
         std::string og = QUtil::int_to_string(stream.getObjectID()) + " " +
             QUtil::int_to_string(stream.getGeneration());
         std::string w_description = "content stream object " + og;
@@ -2920,13 +2907,11 @@ QPDFObjectHandle::copyObject(
         QTC::TC("qpdf", "QPDFObjectHandle clone dictionary");
         std::set<std::string> keys = getKeys();
         std::map<std::string, QPDFObjectHandle> items;
-        for (std::set<std::string>::iterator iter = keys.begin();
-             iter != keys.end();
-             ++iter) {
-            items[*iter] = getKey(*iter);
+        for (auto const& key: keys) {
+            items[key] = getKey(key);
             if ((!first_level_only) &&
-                (cross_indirect || (!items[*iter].isIndirect()))) {
-                items[*iter].copyObject(
+                (cross_indirect || (!items[key].isIndirect()))) {
+                items[key].copyObject(
                     visited, cross_indirect, first_level_only, stop_at_streams);
             }
         }
diff --git a/libqpdf/QPDFPageDocumentHelper.cc b/libqpdf/QPDFPageDocumentHelper.cc
index 61eba8c3..f54ad843 100644
--- a/libqpdf/QPDFPageDocumentHelper.cc
+++ b/libqpdf/QPDFPageDocumentHelper.cc
@@ -14,10 +14,8 @@ QPDFPageDocumentHelper::getAllPages()
 {
     std::vector<QPDFObjectHandle> const& pages_v = this->qpdf.getAllPages();
     std::vector<QPDFPageObjectHelper> pages;
-    for (std::vector<QPDFObjectHandle>::const_iterator iter = pages_v.begin();
-         iter != pages_v.end();
-         ++iter) {
-        pages.push_back(QPDFPageObjectHelper(*iter));
+    for (auto const& iter: pages_v) {
+        pages.push_back(QPDFPageObjectHelper(iter));
     }
     return pages;
 }
@@ -32,10 +30,8 @@ void
 QPDFPageDocumentHelper::removeUnreferencedResources()
 {
     std::vector<QPDFPageObjectHelper> pages = getAllPages();
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter) {
-        (*iter).removeUnreferencedResources();
+    for (auto& ph: pages) {
+        ph.removeUnreferencedResources();
     }
 }
 
@@ -71,10 +67,7 @@ QPDFPageDocumentHelper::flattenAnnotations(
                             " so form fields will not be flattened");
     }
     std::vector<QPDFPageObjectHelper> pages = getAllPages();
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter) {
-        QPDFPageObjectHelper ph(*iter);
+    for (auto& ph: pages) {
         QPDFObjectHandle resources = ph.getAttribute("/Resources", true);
         if (!resources.isDictionary()) {
             // This should never happen and is not exercised in the
@@ -107,11 +100,7 @@ QPDFPageDocumentHelper::flattenAnnotationsForPage(
         rotate = rotate_obj.getIntValueAsInt();
     }
     int next_fx = 1;
-    for (std::vector<QPDFAnnotationObjectHelper>::iterator iter =
-             annots.begin();
-         iter != annots.end();
-         ++iter) {
-        QPDFAnnotationObjectHelper& aoh(*iter);
+    for (auto& aoh: annots) {
         QPDFObjectHandle as = aoh.getAppearanceStream("/N");
         bool is_widget = (aoh.getSubtype() == "/Widget");
         bool process = true;
diff --git a/libqpdf/QPDFTokenizer.cc b/libqpdf/QPDFTokenizer.cc
index 5f70542e..a38b9ef8 100644
--- a/libqpdf/QPDFTokenizer.cc
+++ b/libqpdf/QPDFTokenizer.cc
@@ -568,10 +568,7 @@ QPDFTokenizer::findEI(std::shared_ptr<InputSource> input)
                 bool found_non_printable = false;
                 bool found_other = false;
                 std::string value = t.getValue();
-                for (std::string::iterator iter = value.begin();
-                     iter != value.end();
-                     ++iter) {
-                    char ch = *iter;
+                for (char ch: value) {
                     if (((ch >= 'a') && (ch <= 'z')) ||
                         ((ch >= 'A') && (ch <= 'Z')) || (ch == '*')) {
                         // Treat '*' as alpha since there are valid
diff --git a/libqpdf/QPDFWriter.cc b/libqpdf/QPDFWriter.cc
index 962a8a6c..215af009 100644
--- a/libqpdf/QPDFWriter.cc
+++ b/libqpdf/QPDFWriter.cc
@@ -755,10 +755,8 @@ QPDFWriter::setEncryptionParameters(
 
     int P = 0;
     // Create the complement of P, then invert.
-    for (std::set<int>::iterator iter = bits_to_clear.begin();
-         iter != bits_to_clear.end();
-         ++iter) {
-        P |= (1 << ((*iter) - 1));
+    for (int b: bits_to_clear) {
+        P |= (1 << (b - 1));
     }
     P = ~P;
 
@@ -1277,11 +1275,8 @@ QPDFWriter::assignCompressedObjectNumbers(QPDFObjGen const& og)
 
     // Reserve numbers for the objects that belong to this object
     // stream.
-    for (std::set<QPDFObjGen>::iterator iter =
-             this->m->object_stream_to_objects[objid].begin();
-         iter != this->m->object_stream_to_objects[objid].end();
-         ++iter) {
-        this->m->obj_renumber[*iter] = this->m->next_objid++;
+    for (auto const& iter: this->m->object_stream_to_objects[objid]) {
+        this->m->obj_renumber[iter] = this->m->next_objid++;
     }
 }
 
@@ -1353,11 +1348,9 @@ QPDFWriter::enqueueObject(QPDFObjectHandle object)
         }
     } else if (object.isDictionary()) {
         std::set<std::string> keys = object.getKeys();
-        for (std::set<std::string>::iterator iter = keys.begin();
-             iter != keys.end();
-             ++iter) {
+        for (auto const& key: keys) {
             if (!this->m->linearized) {
-                enqueueObject(object.getKey(*iter));
+                enqueueObject(object.getKey(key));
             }
         }
     } else {
@@ -1401,10 +1394,7 @@ QPDFWriter::writeTrailer(
         writeString(QUtil::int_to_string(size));
     } else {
         std::set<std::string> keys = trailer.getKeys();
-        for (std::set<std::string>::iterator iter = keys.begin();
-             iter != keys.end();
-             ++iter) {
-            std::string const& key = *iter;
+        for (auto const& key: keys) {
             writeStringQDF("  ");
             writeStringNoQDF(" ");
             writeString(QPDF_Name::normalizeName(key));
@@ -1758,11 +1748,7 @@ QPDFWriter::unparseObject(
         writeStringQDF("\n");
 
         std::set<std::string> keys = object.getKeys();
-        for (std::set<std::string>::iterator iter = keys.begin();
-             iter != keys.end();
-             ++iter) {
-            std::string const& key = *iter;
-
+        for (auto const& key: keys) {
             writeStringQDF(indent);
             writeStringQDF("  ");
             writeStringNoQDF(" ");
@@ -1930,12 +1916,9 @@ QPDFWriter::writeObjectStream(QPDFObjectHandle object)
             pushDiscardFilter(pp_ostream);
         } else {
             // Adjust offsets to skip over comment before first object
-
             first = offsets.at(0);
-            for (std::vector<qpdf_offset_t>::iterator iter = offsets.begin();
-                 iter != offsets.end();
-                 ++iter) {
-                *iter -= first;
+            for (auto& iter: offsets) {
+                iter -= first;
             }
 
             // Take one pass at writing pairs of numbers so we can get
@@ -1960,12 +1943,9 @@ QPDFWriter::writeObjectStream(QPDFObjectHandle object)
             writeObjectStreamOffsets(offsets, first_obj);
         }
 
-        int count = 0;
-        for (std::set<QPDFObjGen>::iterator iter =
-                 this->m->object_stream_to_objects[old_id].begin();
-             iter != this->m->object_stream_to_objects[old_id].end();
-             ++iter, ++count) {
-            QPDFObjGen obj = *iter;
+        int count = -1;
+        for (auto const& obj: this->m->object_stream_to_objects[old_id]) {
+            ++count;
             int new_obj = this->m->obj_renumber[obj];
             if (first_obj == -1) {
                 first_obj = new_obj;
@@ -2197,10 +2177,8 @@ QPDFWriter::generateID()
         if (trailer.hasKey("/Info")) {
             QPDFObjectHandle info = trailer.getKey("/Info");
             std::set<std::string> keys = info.getKeys();
-            for (std::set<std::string>::iterator iter = keys.begin();
-                 iter != keys.end();
-                 ++iter) {
-                QPDFObjectHandle obj = info.getKey(*iter);
+            for (auto const& key: keys) {
+                QPDFObjectHandle obj = info.getKey(key);
                 if (obj.isString()) {
                     seed += " ";
                     seed += obj.getStringValue();
@@ -2235,10 +2213,7 @@ QPDFWriter::initializeSpecialStreams()
     // normalizing.
     std::vector<QPDFObjectHandle> pages = this->m->pdf.getAllPages();
     int num = 0;
-    for (std::vector<QPDFObjectHandle>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter) {
-        QPDFObjectHandle& page = *iter;
+    for (auto& page: pages) {
         this->m->page_object_to_seq[page.getObjGen()] = ++num;
         QPDFObjectHandle contents = page.getKey("/Contents");
         std::vector<QPDFObjGen> contents_objects;
@@ -2322,9 +2297,7 @@ QPDFWriter::generateObjectStreams()
     }
     unsigned int n = 0;
     int cur_ostream = 0;
-    for (std::vector<QPDFObjGen>::const_iterator iter = eligible.begin();
-         iter != eligible.end();
-         ++iter) {
+    for (auto const& iter: eligible) {
         if ((n % n_per) == 0) {
             if (n > 0) {
                 QTC::TC("qpdf", "QPDFWriter generate >1 ostream");
@@ -2339,7 +2312,7 @@ QPDFWriter::generateObjectStreams()
                 this->m->pdf.makeIndirectObject(QPDFObjectHandle::newNull())
                     .getObjectID();
         }
-        this->m->object_to_object_stream[*iter] = cur_ostream;
+        this->m->object_to_object_stream[iter] = cur_ostream;
         ++n;
     }
 }
@@ -2495,10 +2468,7 @@ QPDFWriter::doWriteSetup()
     if (this->m->linearized) {
         // Page dictionaries are not allowed to be compressed objects.
         std::vector<QPDFObjectHandle> pages = this->m->pdf.getAllPages();
-        for (std::vector<QPDFObjectHandle>::iterator iter = pages.begin();
-             iter != pages.end();
-             ++iter) {
-            QPDFObjectHandle& page = *iter;
+        for (auto& page: pages) {
             QPDFObjGen og = page.getObjGen();
             if (this->m->object_to_object_stream.count(og)) {
                 QTC::TC("qpdf", "QPDFWriter uncompressing page dictionary");
@@ -2521,12 +2491,9 @@ QPDFWriter::doWriteSetup()
     }
 
     // Generate reverse mapping from object stream to objects
-    for (std::map<QPDFObjGen, int>::iterator iter =
-             this->m->object_to_object_stream.begin();
-         iter != this->m->object_to_object_stream.end();
-         ++iter) {
-        QPDFObjGen obj = (*iter).first;
-        int stream = (*iter).second;
+    for (auto const& iter: this->m->object_to_object_stream) {
+        QPDFObjGen const& obj = iter.first;
+        int stream = iter.second;
         this->m->object_stream_to_objects[stream].insert(obj);
         this->m->max_ostream_index = std::max(
             this->m->max_ostream_index,
@@ -2591,11 +2558,9 @@ QPDFWriter::getWrittenXRefTable()
 {
     std::map<QPDFObjGen, QPDFXRefEntry> result;
 
-    for (std::map<int, QPDFXRefEntry>::iterator iter = this->m->xref.begin();
-         iter != this->m->xref.end();
-         ++iter) {
-        if (iter->first != 0 && iter->second.getType() != 0) {
-            result[QPDFObjGen(iter->first, 0)] = iter->second;
+    for (auto const& iter: this->m->xref) {
+        if (iter.first != 0 && iter.second.getType() != 0) {
+            result[QPDFObjGen(iter.first, 0)] = iter.second;
         }
     }
 
@@ -2605,10 +2570,8 @@ QPDFWriter::getWrittenXRefTable()
 void
 QPDFWriter::enqueuePart(std::vector<QPDFObjectHandle>& part)
 {
-    for (std::vector<QPDFObjectHandle>::iterator iter = part.begin();
-         iter != part.end();
-         ++iter) {
-        enqueueObject(*iter);
+    for (auto const& oh: part) {
+        enqueueObject(oh);
     }
 }
 
@@ -2617,14 +2580,11 @@ QPDFWriter::writeEncryptionDictionary()
 {
     this->m->encryption_dict_objid = openObject(this->m->encryption_dict_objid);
     writeString("<<");
-    for (std::map<std::string, std::string>::iterator iter =
-             this->m->encryption_dictionary.begin();
-         iter != this->m->encryption_dictionary.end();
-         ++iter) {
+    for (auto const& iter: this->m->encryption_dictionary) {
         writeString(" ");
-        writeString((*iter).first);
+        writeString(iter.first);
         writeString(" ");
-        writeString((*iter).second);
+        writeString(iter.second);
     }
     writeString(" >>");
     closeObject(this->m->encryption_dict_objid);
@@ -2937,10 +2897,8 @@ QPDFWriter::discardGeneration(
     // maps for QPDF that throw away generation numbers.
 
     out.clear();
-    for (std::map<QPDFObjGen, int>::const_iterator iter = in.begin();
-         iter != in.end();
-         ++iter) {
-        if (out.count((*iter).first.getObj())) {
+    for (auto const& iter: in) {
+        if (out.count(iter.first.getObj())) {
             throw std::runtime_error(
                 "QPDF cannot currently linearize files that contain"
                 " multiple objects with the same object ID and different"
@@ -2950,7 +2908,7 @@ QPDFWriter::discardGeneration(
                 " linearizing, and then linearize the result of that"
                 " conversion.");
         }
-        out[(*iter).first.getObj()] = (*iter).second;
+        out[iter.first.getObj()] = iter.second;
     }
 }
 
@@ -3020,10 +2978,8 @@ QPDFWriter::writeLinearized()
     // Assign numbers to all compressed objects in the second half.
     std::vector<QPDFObjectHandle>* vecs2[] = {&part7, &part8, &part9};
     for (int i = 0; i < 3; ++i) {
-        for (std::vector<QPDFObjectHandle>::iterator iter = (*vecs2[i]).begin();
-             iter != (*vecs2[i]).end();
-             ++iter) {
-            assignCompressedObjectNumbers((*iter).getObjGen());
+        for (auto const& oh: *vecs2[i]) {
+            assignCompressedObjectNumbers(oh.getObjGen());
         }
     }
     int second_half_end = this->m->next_objid - 1;
@@ -3049,10 +3005,8 @@ QPDFWriter::writeLinearized()
     // Assign numbers to all compressed objects in the first half
     std::vector<QPDFObjectHandle>* vecs1[] = {&part4, &part6};
     for (int i = 0; i < 2; ++i) {
-        for (std::vector<QPDFObjectHandle>::iterator iter = (*vecs1[i]).begin();
-             iter != (*vecs1[i]).end();
-             ++iter) {
-            assignCompressedObjectNumbers((*iter).getObjGen());
+        for (auto const& oh: *vecs1[i]) {
+            assignCompressedObjectNumbers(oh.getObjGen());
         }
     }
     int first_half_end = this->m->next_objid - 1;
@@ -3240,11 +3194,7 @@ QPDFWriter::writeLinearized()
 
         // Parts 4 through 9
 
-        for (std::list<QPDFObjectHandle>::iterator iter =
-                 this->m->object_queue.begin();
-             iter != this->m->object_queue.end();
-             ++iter) {
-            QPDFObjectHandle cur_object = (*iter);
+        for (auto const& cur_object: this->m->object_queue) {
             if (cur_object.getObjectID() == part6_end_marker) {
                 first_half_max_obj_offset = this->m->pipeline->getCount();
             }
@@ -3390,11 +3340,8 @@ QPDFWriter::enqueueObjectsStandard()
 {
     if (this->m->preserve_unreferenced_objects) {
         QTC::TC("qpdf", "QPDFWriter preserve unreferenced standard");
-        std::vector<QPDFObjectHandle> all = this->m->pdf.getAllObjects();
-        for (std::vector<QPDFObjectHandle>::iterator iter = all.begin();
-             iter != all.end();
-             ++iter) {
-            enqueueObject(*iter);
+        for (auto const& oh: this->m->pdf.getAllObjects()) {
+            enqueueObject(oh);
         }
     }
 
@@ -3407,10 +3354,8 @@ QPDFWriter::enqueueObjectsStandard()
     // Root is already there, so enqueuing it a second time is a
     // no-op.
     std::set<std::string> keys = trailer.getKeys();
-    for (std::set<std::string>::iterator iter = keys.begin();
-         iter != keys.end();
-         ++iter) {
-        enqueueObject(trailer.getKey(*iter));
+    for (auto const& key: keys) {
+        enqueueObject(trailer.getKey(key));
     }
 }
 
@@ -3424,23 +3369,18 @@ QPDFWriter::enqueueObjectsPCLm()
 
     // enqueue all pages first
     std::vector<QPDFObjectHandle> all = this->m->pdf.getAllPages();
-    for (std::vector<QPDFObjectHandle>::iterator iter = all.begin();
-         iter != all.end();
-         ++iter) {
+    for (auto& page: all) {
         // enqueue page
-        enqueueObject(*iter);
+        enqueueObject(page);
 
         // enqueue page contents stream
-        enqueueObject((*iter).getKey("/Contents"));
+        enqueueObject(page.getKey("/Contents"));
 
         // enqueue all the strips for each page
-        QPDFObjectHandle strips =
-            (*iter).getKey("/Resources").getKey("/XObject");
+        QPDFObjectHandle strips = page.getKey("/Resources").getKey("/XObject");
         std::set<std::string> keys = strips.getKeys();
-        for (std::set<std::string>::iterator image = keys.begin();
-             image != keys.end();
-             ++image) {
-            enqueueObject(strips.getKey(*image));
+        for (auto const& image: keys) {
+            enqueueObject(strips.getKey(image));
             enqueueObject(QPDFObjectHandle::newStream(
                 &this->m->pdf, image_transform_content));
         }
diff --git a/libqpdf/QPDF_Array.cc b/libqpdf/QPDF_Array.cc
index 0567f66b..8899bf6f 100644
--- a/libqpdf/QPDF_Array.cc
+++ b/libqpdf/QPDF_Array.cc
@@ -99,10 +99,8 @@ void
 QPDF_Array::setFromVector(std::vector<QPDFObjectHandle> const& v)
 {
     this->elements = SparseOHArray();
-    for (std::vector<QPDFObjectHandle>::const_iterator iter = v.begin();
-         iter != v.end();
-         ++iter) {
-        this->elements.append(*iter);
+    for (auto const& iter: v) {
+        this->elements.append(iter);
     }
 }
 
diff --git a/libqpdf/QPDF_Dictionary.cc b/libqpdf/QPDF_Dictionary.cc
index e5b88027..44b8a474 100644
--- a/libqpdf/QPDF_Dictionary.cc
+++ b/libqpdf/QPDF_Dictionary.cc
@@ -12,11 +12,8 @@ QPDF_Dictionary::QPDF_Dictionary(
 void
 QPDF_Dictionary::releaseResolved()
 {
-    for (std::map<std::string, QPDFObjectHandle>::iterator iter =
-             this->items.begin();
-         iter != this->items.end();
-         ++iter) {
-        QPDFObjectHandle::ReleaseResolver::releaseResolved((*iter).second);
+    for (auto& iter: this->items) {
+        QPDFObjectHandle::ReleaseResolver::releaseResolved(iter.second);
     }
 }
 
diff --git a/libqpdf/QPDF_encryption.cc b/libqpdf/QPDF_encryption.cc
index 00920082..b943777f 100644
--- a/libqpdf/QPDF_encryption.cc
+++ b/libqpdf/QPDF_encryption.cc
@@ -945,11 +945,7 @@ QPDF::initializeEncryption()
 
     if ((V == 4) || (V == 5)) {
         QPDFObjectHandle CF = encryption_dict.getKey("/CF");
-        std::set<std::string> keys = CF.getKeys();
-        for (std::set<std::string>::iterator iter = keys.begin();
-             iter != keys.end();
-             ++iter) {
-            std::string const& filter = *iter;
+        for (auto const& filter: CF.getKeys()) {
             QPDFObjectHandle cdict = CF.getKey(filter);
             if (cdict.isDictionary()) {
                 encryption_method_e method = e_none;
diff --git a/libqpdf/QPDF_linearization.cc b/libqpdf/QPDF_linearization.cc
index cdeb89a9..ec422406 100644
--- a/libqpdf/QPDF_linearization.cc
+++ b/libqpdf/QPDF_linearization.cc
@@ -583,12 +583,9 @@ QPDF::checkLinearizationInternal()
     // uncompressed.
     { // local scope
         std::map<int, int> object_stream_data;
-        for (std::map<QPDFObjGen, QPDFXRefEntry>::const_iterator iter =
-                 this->m->xref_table.begin();
-             iter != this->m->xref_table.end();
-             ++iter) {
-            QPDFObjGen const& og = (*iter).first;
-            QPDFXRefEntry const& entry = (*iter).second;
+        for (auto const& iter: this->m->xref_table) {
+            QPDFObjGen const& og = iter.first;
+            QPDFXRefEntry const& entry = iter.second;
             if (entry.getType() == 2) {
                 object_stream_data[og.getObj()] = entry.getObjStreamNumber();
             }
@@ -613,10 +610,8 @@ QPDF::checkLinearizationInternal()
     }
     qpdf_offset_t min_E = -1;
     qpdf_offset_t max_E = -1;
-    for (std::vector<QPDFObjectHandle>::iterator iter = this->m->part6.begin();
-         iter != this->m->part6.end();
-         ++iter) {
-        QPDFObjGen og((*iter).getObjGen());
+    for (auto const& oh: this->m->part6) {
+        QPDFObjGen og(oh.getObjGen());
         if (this->m->obj_cache.count(og) == 0) {
             // All objects have to have been dereferenced to be classified.
             throw std::logic_error("linearization part6 object not in cache");
@@ -651,19 +646,15 @@ QPDF::checkLinearizationInternal()
     // code.
     if (!errors.empty()) {
         result = false;
-        for (std::list<std::string>::iterator iter = errors.begin();
-             iter != errors.end();
-             ++iter) {
-            *this->m->err_stream << "WARNING: " << (*iter) << std::endl;
+        for (auto const& error: errors) {
+            *this->m->err_stream << "WARNING: " << error << std::endl;
         }
     }
 
     if (!warnings.empty()) {
         result = false;
-        for (std::list<std::string>::iterator iter = warnings.begin();
-             iter != warnings.end();
-             ++iter) {
-            *this->m->err_stream << "WARNING: " << (*iter) << std::endl;
+        for (auto const& warning: warnings) {
+            *this->m->err_stream << "WARNING: " << warning << std::endl;
         }
     }
 
@@ -678,10 +669,7 @@ QPDF::maxEnd(ObjUser const& ou)
     }
     std::set<QPDFObjGen> const& ogs = this->m->obj_user_to_objects[ou];
     qpdf_offset_t end = 0;
-    for (std::set<QPDFObjGen>::const_iterator iter = ogs.begin();
-         iter != ogs.end();
-         ++iter) {
-        QPDFObjGen const& og = *iter;
+    for (auto const& og: ogs) {
         if (this->m->obj_cache.count(og) == 0) {
             stopOnError("unknown object referenced in object user table");
         }
@@ -855,28 +843,24 @@ QPDF::checkHPageOffset(
             computed_shared.insert(obj);
         }
 
-        for (std::set<int>::iterator iter = hint_shared.begin();
-             iter != hint_shared.end();
-             ++iter) {
-            if (!computed_shared.count(*iter)) {
+        for (int iter: hint_shared) {
+            if (!computed_shared.count(iter)) {
                 // pdlin puts thumbnails here even though it shouldn't
                 warnings.push_back(
                     "page " + QUtil::int_to_string(pageno) +
-                    ": shared object " + QUtil::int_to_string(*iter) +
+                    ": shared object " + QUtil::int_to_string(iter) +
                     ": in hint table but not computed list");
             }
         }
 
-        for (std::set<int>::iterator iter = computed_shared.begin();
-             iter != computed_shared.end();
-             ++iter) {
-            if (!hint_shared.count(*iter)) {
+        for (int iter: computed_shared) {
+            if (!hint_shared.count(iter)) {
                 // Acrobat does not put some things including at least
                 // built-in fonts and procsets here, at least in some
                 // cases.
                 warnings.push_back(
                     "page " + QUtil::int_to_string(pageno) +
-                    ": shared object " + QUtil::int_to_string(*iter) +
+                    ": shared object " + QUtil::int_to_string(iter) +
                     ": in computed list but not hint table");
             }
         }
@@ -1290,13 +1274,9 @@ QPDF::calculateLinearizationData(std::map<int, int> const& object_stream_data)
     std::set<QPDFObjGen> lc_outlines;
     std::set<QPDFObjGen> lc_root;
 
-    for (std::map<QPDFObjGen, std::set<ObjUser>>::iterator oiter =
-             this->m->object_to_obj_users.begin();
-         oiter != this->m->object_to_obj_users.end();
-         ++oiter) {
-        QPDFObjGen const& og = (*oiter).first;
-
-        std::set<ObjUser>& ous = (*oiter).second;
+    for (auto& oiter: this->m->object_to_obj_users) {
+        QPDFObjGen const& og = oiter.first;
+        std::set<ObjUser>& ous = oiter.second;
 
         bool in_open_document = false;
         bool in_first_page = false;
@@ -1306,10 +1286,7 @@ QPDF::calculateLinearizationData(std::map<int, int> const& object_stream_data)
         bool in_outlines = false;
         bool is_root = false;
 
-        for (std::set<ObjUser>::iterator uiter = ous.begin();
-             uiter != ous.end();
-             ++uiter) {
-            ObjUser const& ou = *uiter;
+        for (auto const& ou: ous) {
             switch (ou.ou_type) {
             case ObjUser::ou_trailer_key:
                 if (ou.key == "/Encrypt") {
@@ -1396,11 +1373,8 @@ QPDF::calculateLinearizationData(std::map<int, int> const& object_stream_data)
     { // local scope
         // Map all page objects to the containing object stream.  This
         // should be a no-op in a properly linearized file.
-        std::vector<QPDFObjectHandle> t = getAllPages();
-        for (std::vector<QPDFObjectHandle>::iterator iter = t.begin();
-             iter != t.end();
-             ++iter) {
-            pages.push_back(getUncompressedObject(*iter, object_stream_data));
+        for (auto oh: getAllPages()) {
+            pages.push_back(getUncompressedObject(oh, object_stream_data));
         }
     }
     int npages = toI(pages.size());
@@ -1427,10 +1401,8 @@ QPDF::calculateLinearizationData(std::map<int, int> const& object_stream_data)
                     " calculating linearization data");
     }
     this->m->part4.push_back(objGenToIndirect(*(lc_root.begin())));
-    for (std::set<QPDFObjGen>::iterator iter = lc_open_document.begin();
-         iter != lc_open_document.end();
-         ++iter) {
-        this->m->part4.push_back(objGenToIndirect(*iter));
+    for (auto const& og: lc_open_document) {
+        this->m->part4.push_back(objGenToIndirect(og));
     }
 
     // Part 6: first page objects.  Note: implementation note 124
@@ -1458,16 +1430,12 @@ QPDF::calculateLinearizationData(std::map<int, int> const& object_stream_data)
     // groups private and shared objects contiguously for the sake of
     // hint tables.
 
-    for (std::set<QPDFObjGen>::iterator iter = lc_first_page_private.begin();
-         iter != lc_first_page_private.end();
-         ++iter) {
-        this->m->part6.push_back(objGenToIndirect(*iter));
+    for (auto const& og: lc_first_page_private) {
+        this->m->part6.push_back(objGenToIndirect(og));
     }
 
-    for (std::set<QPDFObjGen>::iterator iter = lc_first_page_shared.begin();
-         iter != lc_first_page_shared.end();
-         ++iter) {
-        this->m->part6.push_back(objGenToIndirect(*iter));
+    for (auto const& og: lc_first_page_shared) {
+        this->m->part6.push_back(objGenToIndirect(og));
     }
 
     // Place the outline dictionary if it goes in the first page section.
@@ -1511,10 +1479,7 @@ QPDF::calculateLinearizationData(std::map<int, int> const& object_stream_data)
                         " calculating linearization data");
         }
         std::set<QPDFObjGen> ogs = this->m->obj_user_to_objects[ou];
-        for (std::set<QPDFObjGen>::iterator iter = ogs.begin();
-             iter != ogs.end();
-             ++iter) {
-            QPDFObjGen const& og = (*iter);
+        for (auto const& og: ogs) {
             if (lc_other_page_private.count(og)) {
                 lc_other_page_private.erase(og);
                 this->m->part7.push_back(objGenToIndirect(og));
@@ -1533,10 +1498,8 @@ QPDF::calculateLinearizationData(std::map<int, int> const& object_stream_data)
     // Part 8: other pages' shared objects
 
     // Order is unimportant.
-    for (std::set<QPDFObjGen>::iterator iter = lc_other_page_shared.begin();
-         iter != lc_other_page_shared.end();
-         ++iter) {
-        this->m->part8.push_back(objGenToIndirect(*iter));
+    for (auto const& og: lc_other_page_shared) {
+        this->m->part8.push_back(objGenToIndirect(og));
     }
 
     // Part 9: other objects
@@ -1555,10 +1518,7 @@ QPDF::calculateLinearizationData(std::map<int, int> const& object_stream_data)
         stopOnError("found empty pages tree while"
                     " calculating linearization data");
     }
-    for (std::set<QPDFObjGen>::iterator iter = pages_ogs.begin();
-         iter != pages_ogs.end();
-         ++iter) {
-        QPDFObjGen const& og = *iter;
+    for (auto const& og: pages_ogs) {
         if (lc_other.count(og)) {
             lc_other.erase(og);
             this->m->part9.push_back(objGenToIndirect(og));
@@ -1588,10 +1548,7 @@ QPDF::calculateLinearizationData(std::map<int, int> const& object_stream_data)
             std::set<QPDFObjGen>& ogs =
                 this->m
                     ->obj_user_to_objects[ObjUser(ObjUser::ou_thumb, toI(i))];
-            for (std::set<QPDFObjGen>::iterator iter = ogs.begin();
-                 iter != ogs.end();
-                 ++iter) {
-                QPDFObjGen const& og = *iter;
+            for (auto const& og: ogs) {
                 if (lc_thumbnail_private.count(og)) {
                     lc_thumbnail_private.erase(og);
                     this->m->part9.push_back(objGenToIndirect(og));
@@ -1606,10 +1563,8 @@ QPDF::calculateLinearizationData(std::map<int, int> const& object_stream_data)
     }
 
     // Place shared thumbnail objects
-    for (std::set<QPDFObjGen>::iterator iter = lc_thumbnail_shared.begin();
-         iter != lc_thumbnail_shared.end();
-         ++iter) {
-        this->m->part9.push_back(objGenToIndirect(*iter));
+    for (auto const& og: lc_thumbnail_shared) {
+        this->m->part9.push_back(objGenToIndirect(og));
     }
 
     // Place outlines unless in first page
@@ -1618,10 +1573,8 @@ QPDF::calculateLinearizationData(std::map<int, int> const& object_stream_data)
     }
 
     // Place all remaining objects
-    for (std::set<QPDFObjGen>::iterator iter = lc_other.begin();
-         iter != lc_other.end();
-         ++iter) {
-        this->m->part9.push_back(objGenToIndirect(*iter));
+    for (auto const& og: lc_other) {
+        this->m->part9.push_back(objGenToIndirect(og));
     }
 
     // Make sure we got everything exactly once.
@@ -1658,10 +1611,7 @@ QPDF::calculateLinearizationData(std::map<int, int> const& object_stream_data)
 
     std::vector<CHSharedObjectEntry>& shared =
         this->m->c_shared_object_data.entries;
-    for (std::vector<QPDFObjectHandle>::iterator iter = this->m->part6.begin();
-         iter != this->m->part6.end();
-         ++iter) {
-        QPDFObjectHandle& oh = *iter;
+    for (auto& oh: this->m->part6) {
         int obj = oh.getObjectID();
         obj_to_index[obj] = toI(shared.size());
         shared.push_back(CHSharedObjectEntry(obj));
@@ -1670,11 +1620,7 @@ QPDF::calculateLinearizationData(std::map<int, int> const& object_stream_data)
     if (!this->m->part8.empty()) {
         this->m->c_shared_object_data.first_shared_obj =
             this->m->part8.at(0).getObjectID();
-        for (std::vector<QPDFObjectHandle>::iterator iter =
-                 this->m->part8.begin();
-             iter != this->m->part8.end();
-             ++iter) {
-            QPDFObjectHandle& oh = *iter;
+        for (auto& oh: this->m->part8) {
             int obj = oh.getObjectID();
             obj_to_index[obj] = toI(shared.size());
             shared.push_back(CHSharedObjectEntry(obj));
@@ -1696,10 +1642,7 @@ QPDF::calculateLinearizationData(std::map<int, int> const& object_stream_data)
                         " calculating linearization data");
         }
         std::set<QPDFObjGen> const& ogs = this->m->obj_user_to_objects[ou];
-        for (std::set<QPDFObjGen>::const_iterator iter = ogs.begin();
-             iter != ogs.end();
-             ++iter) {
-            QPDFObjGen const& og = *iter;
+        for (auto const& og: ogs) {
             if ((this->m->object_to_obj_users[og].size() > 1) &&
                 (obj_to_index.count(og.getObj()) > 0)) {
                 int idx = obj_to_index[og.getObj()];
@@ -1733,10 +1676,8 @@ QPDF::pushOutlinesToPart(
     this->m->c_outline_data.nobjects = 1;
     lc_outlines.erase(outlines_og);
     part.push_back(outlines);
-    for (std::set<QPDFObjGen>::iterator iter = lc_outlines.begin();
-         iter != lc_outlines.end();
-         ++iter) {
-        part.push_back(objGenToIndirect(*iter));
+    for (auto const& og: lc_outlines) {
+        part.push_back(objGenToIndirect(og));
         ++this->m->c_outline_data.nobjects;
     }
 }
diff --git a/libqpdf/QPDF_optimization.cc b/libqpdf/QPDF_optimization.cc
index 0c453126..d22aa378 100644
--- a/libqpdf/QPDF_optimization.cc
+++ b/libqpdf/QPDF_optimization.cc
@@ -90,10 +90,7 @@ QPDF::optimize(
 
     // Traverse document-level items
     std::set<std::string> keys = this->m->trailer.getKeys();
-    for (std::set<std::string>::iterator iter = keys.begin();
-         iter != keys.end();
-         ++iter) {
-        std::string const& key = *iter;
+    for (auto const& key: keys) {
         if (key == "/Root") {
             // handled separately
         } else {
@@ -105,17 +102,13 @@ QPDF::optimize(
     }
 
     keys = root.getKeys();
-    for (std::set<std::string>::iterator iter = keys.begin();
-         iter != keys.end();
-         ++iter) {
+    for (auto const& key: keys) {
         // Technically, /I keys from /Thread dictionaries are supposed
         // to be handled separately, but we are going to disregard
         // that specification for now.  There is loads of evidence
         // that pdlin and Acrobat both disregard things like this from
         // time to time, so this is almost certain not to cause any
         // problems.
-
-        std::string const& key = *iter;
         updateObjectMaps(
             ObjUser(ObjUser::ou_root_key, key),
             root.getKey(key),
@@ -212,10 +205,7 @@ QPDF::pushInheritedAttributesToPageInternal(
 
         std::set<std::string> inheritable_keys;
         std::set<std::string> keys = cur_pages.getKeys();
-        for (std::set<std::string>::iterator iter = keys.begin();
-             iter != keys.end();
-             ++iter) {
-            std::string const& key = *iter;
+        for (auto const& key: keys) {
             if ((key == "/MediaBox") || (key == "/CropBox") ||
                 (key == "/Resources") || (key == "/Rotate")) {
                 if (!allow_changes) {
@@ -298,11 +288,7 @@ QPDF::pushInheritedAttributesToPageInternal(
 
         if (!inheritable_keys.empty()) {
             QTC::TC("qpdf", "QPDF opt inheritable keys");
-            for (std::set<std::string>::iterator iter =
-                     inheritable_keys.begin();
-                 iter != inheritable_keys.end();
-                 ++iter) {
-                std::string const& key = (*iter);
+            for (auto const& key: inheritable_keys) {
                 key_ancestors[key].pop_back();
                 if (key_ancestors[key].empty()) {
                     QTC::TC("qpdf", "QPDF opt erase empty key ancestor");
@@ -315,14 +301,11 @@ QPDF::pushInheritedAttributesToPageInternal(
     } else if (type == "/Page") {
         // Add all available inheritable attributes not present in
         // this object to this object.
-        for (std::map<std::string, std::vector<QPDFObjectHandle>>::iterator
-                 iter = key_ancestors.begin();
-             iter != key_ancestors.end();
-             ++iter) {
-            std::string const& key = (*iter).first;
+        for (auto const& iter: key_ancestors) {
+            std::string const& key = iter.first;
             if (!cur_pages.hasKey(key)) {
                 QTC::TC("qpdf", "QPDF opt resource inherited");
-                cur_pages.replaceKey(key, (*iter).second.back());
+                cur_pages.replaceKey(key, iter.second.back());
             } else {
                 QTC::TC("qpdf", "QPDF opt page resource hides ancestor");
             }
@@ -404,10 +387,7 @@ QPDF::updateObjectMapsInternal(
         }
 
         std::set<std::string> keys = dict.getKeys();
-        for (std::set<std::string>::iterator iter = keys.begin();
-             iter != keys.end();
-             ++iter) {
-            std::string const& key = *iter;
+        for (auto const& key: keys) {
             if (is_page_node && (key == "/Thumb")) {
                 // Traverse page thumbnail dictionaries as a special
                 // case.
@@ -454,42 +434,28 @@ QPDF::filterCompressedObjects(std::map<int, int> const& object_stream_data)
     std::map<ObjUser, std::set<QPDFObjGen>> t_obj_user_to_objects;
     std::map<QPDFObjGen, std::set<ObjUser>> t_object_to_obj_users;
 
-    for (std::map<ObjUser, std::set<QPDFObjGen>>::iterator i1 =
-             this->m->obj_user_to_objects.begin();
-         i1 != this->m->obj_user_to_objects.end();
-         ++i1) {
-        ObjUser const& ou = (*i1).first;
-        std::set<QPDFObjGen> const& objects = (*i1).second;
-        for (std::set<QPDFObjGen>::const_iterator i2 = objects.begin();
-             i2 != objects.end();
-             ++i2) {
-            QPDFObjGen const& og = (*i2);
-            std::map<int, int>::const_iterator i3 =
-                object_stream_data.find(og.getObj());
-            if (i3 == object_stream_data.end()) {
+    for (auto const& i1: this->m->obj_user_to_objects) {
+        ObjUser const& ou = i1.first;
+        std::set<QPDFObjGen> const& objects = i1.second;
+        for (auto const& og: objects) {
+            auto i2 = object_stream_data.find(og.getObj());
+            if (i2 == object_stream_data.end()) {
                 t_obj_user_to_objects[ou].insert(og);
             } else {
-                t_obj_user_to_objects[ou].insert(QPDFObjGen((*i3).second, 0));
+                t_obj_user_to_objects[ou].insert(QPDFObjGen(i2->second, 0));
             }
         }
     }
 
-    for (std::map<QPDFObjGen, std::set<ObjUser>>::iterator i1 =
-             this->m->object_to_obj_users.begin();
-         i1 != this->m->object_to_obj_users.end();
-         ++i1) {
-        QPDFObjGen const& og = (*i1).first;
-        std::set<ObjUser> const& objusers = (*i1).second;
-        for (std::set<ObjUser>::const_iterator i2 = objusers.begin();
-             i2 != objusers.end();
-             ++i2) {
-            ObjUser const& ou = (*i2);
-            std::map<int, int>::const_iterator i3 =
-                object_stream_data.find(og.getObj());
-            if (i3 == object_stream_data.end()) {
+    for (auto const& i1: this->m->object_to_obj_users) {
+        QPDFObjGen const& og = i1.first;
+        std::set<ObjUser> const& objusers = i1.second;
+        for (auto const& ou: objusers) {
+            auto i2 = object_stream_data.find(og.getObj());
+            if (i2 == object_stream_data.end()) {
                 t_object_to_obj_users[og].insert(ou);
             } else {
-                t_object_to_obj_users[QPDFObjGen((*i3).second, 0)].insert(ou);
+                t_object_to_obj_users[QPDFObjGen(i2->second, 0)].insert(ou);
             }
         }
     }
diff --git a/libqpdf/QPDF_pages.cc b/libqpdf/QPDF_pages.cc
index c2b2dd1a..89a782f4 100644
--- a/libqpdf/QPDF_pages.cc
+++ b/libqpdf/QPDF_pages.cc
@@ -319,8 +319,7 @@ int
 QPDF::findPage(QPDFObjGen const& og)
 {
     flattenPagesTree();
-    std::map<QPDFObjGen, int>::iterator it =
-        this->m->pageobj_to_pages_pos.find(og);
+    auto it = this->m->pageobj_to_pages_pos.find(og);
     if (it == this->m->pageobj_to_pages_pos.end()) {
         QTC::TC("qpdf", "QPDF_pages findPage not found");
         setLastObjectDescription("page object", og.getObj(), og.getGen());
diff --git a/libqpdf/QUtil.cc b/libqpdf/QUtil.cc
index 5fa6c4b9..22962199 100644
--- a/libqpdf/QUtil.cc
+++ b/libqpdf/QUtil.cc
@@ -786,14 +786,13 @@ QUtil::hex_decode(std::string const& input)
 {
     std::string result;
     size_t pos = 0;
-    for (std::string::const_iterator p = input.begin(); p != input.end(); ++p) {
-        char ch = *p;
+    for (auto ch: input) {
         bool skip = false;
-        if ((*p >= 'A') && (*p <= 'F')) {
+        if ((ch >= 'A') && (ch <= 'F')) {
             ch = QIntC::to_char(ch - 'A' + 10);
-        } else if ((*p >= 'a') && (*p <= 'f')) {
+        } else if ((ch >= 'a') && (ch <= 'f')) {
             ch = QIntC::to_char(ch - 'a' + 10);
-        } else if ((*p >= '0') && (*p <= '9')) {
+        } else if ((ch >= '0') && (ch <= '9')) {
             ch = QIntC::to_char(ch - '0');
         } else {
             skip = true;
@@ -1921,12 +1920,10 @@ QUtil::possible_repaired_encodings(std::string supplied)
     // De-duplicate
     std::vector<std::string> t;
     std::set<std::string> seen;
-    for (std::vector<std::string>::iterator iter = result.begin();
-         iter != result.end();
-         ++iter) {
-        if (!seen.count(*iter)) {
-            seen.insert(*iter);
-            t.push_back(*iter);
+    for (auto const& iter: result) {
+        if (!seen.count(iter)) {
+            seen.insert(iter);
+            t.push_back(iter);
         }
     }
     return t;
diff --git a/libtests/json.cc b/libtests/json.cc
index 17a5d574..43f2b3c6 100644
--- a/libtests/json.cc
+++ b/libtests/json.cc
@@ -130,10 +130,8 @@ check_schema(
     std::list<std::string> errors;
     std::cout << "--- " << description << std::endl;
     assert(exp == obj.checkSchema(schema, flags, errors));
-    for (std::list<std::string>::iterator iter = errors.begin();
-         iter != errors.end();
-         ++iter) {
-        std::cout << *iter << std::endl;
+    for (auto const& error: errors) {
+        std::cout << error << std::endl;
     }
     std::cout << "---" << std::endl;
 }
diff --git a/libtests/numrange.cc b/libtests/numrange.cc
index d1548fe9..c0bf5bd7 100644
--- a/libtests/numrange.cc
+++ b/libtests/numrange.cc
@@ -9,10 +9,8 @@ test_numrange(char const* range)
     } else {
         std::vector<int> result = QUtil::parse_numrange(range, 15);
         std::cout << "numeric range " << range << " ->";
-        for (std::vector<int>::iterator iter = result.begin();
-             iter != result.end();
-             ++iter) {
-            std::cout << " " << *iter;
+        for (int i: result) {
+            std::cout << " " << i;
         }
         std::cout << std::endl;
     }
diff --git a/libtests/qutil.cc b/libtests/qutil.cc
index eb16bf0b..017f371b 100644
--- a/libtests/qutil.cc
+++ b/libtests/qutil.cc
@@ -229,12 +229,10 @@ print_utf8(unsigned long val)
         // Emacs has trouble with utf-8 encoding files with characters
         // outside the 16-bit portion, so just show the character
         // values.
-        for (std::string::iterator iter = result.begin(); iter != result.end();
-             ++iter) {
+        for (auto const& ch: result) {
             std::cout << " "
                       << QUtil::int_to_string_base(
-                             static_cast<int>(
-                                 static_cast<unsigned char>(*iter)),
+                             static_cast<int>(static_cast<unsigned char>(ch)),
                              16,
                              2);
         }
@@ -289,11 +287,10 @@ print_utf16(unsigned long val)
 {
     std::string result = QUtil::toUTF16(val);
     std::cout << "0x" << QUtil::uint_to_string_base(val, 16) << " ->";
-    for (std::string::iterator iter = result.begin(); iter != result.end();
-         ++iter) {
+    for (auto const& ch: result) {
         std::cout << " "
                   << QUtil::int_to_string_base(
-                         static_cast<int>(static_cast<unsigned char>(*iter)),
+                         static_cast<int>(static_cast<unsigned char>(ch)),
                          16,
                          2);
     }
@@ -516,10 +513,8 @@ void
 read_from_file_test()
 {
     std::list<std::string> lines = QUtil::read_lines_from_file("other-file");
-    for (std::list<std::string>::iterator iter = lines.begin();
-         iter != lines.end();
-         ++iter) {
-        std::cout << *iter << std::endl;
+    for (auto const& line: lines) {
+        std::cout << line << std::endl;
     }
     // Test the other versions and make sure we get the same results
     {
diff --git a/qpdf/test_driver.cc b/qpdf/test_driver.cc
index e0e77cfe..f0c56176 100644
--- a/qpdf/test_driver.cc
+++ b/qpdf/test_driver.cc
@@ -383,14 +383,9 @@ test_5(QPDF& pdf, char const* arg2)
     QPDFPageDocumentHelper dh(pdf);
     std::vector<QPDFPageObjectHelper> pages = dh.getAllPages();
     int pageno = 0;
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter) {
-        QPDFPageObjectHelper& page(*iter);
+    for (auto& page: pages) {
         ++pageno;
-
         std::cout << "page " << pageno << ":" << std::endl;
-
         std::cout << "  images:" << std::endl;
         std::map<std::string, QPDFObjectHandle> images = page.getImages();
         for (auto const& iter2: images) {
@@ -714,19 +709,19 @@ test_15(QPDF& pdf, char const* arg2)
     // a shallow copy.
     QPDFObjectHandle page_template = pages.at(0);
     std::vector<QPDFObjectHandle> new_pages;
-    for (std::vector<QPDFObjectHandle>::iterator iter = contents.begin();
-         iter != contents.end();
-         ++iter) {
+    bool first = true;
+    for (auto const& iter: contents) {
         // We will retain indirect object references to other
         // indirect objects other than page content.
         QPDFObjectHandle page = page_template.shallowCopy();
-        page.replaceKey("/Contents", *iter);
-        if (iter == contents.begin()) {
+        page.replaceKey("/Contents", iter);
+        if (first) {
             // leave direct
-            new_pages.push_back(page);
+            first = false;
         } else {
-            new_pages.push_back(pdf.makeIndirectObject(page));
+            page = pdf.makeIndirectObject(page);
         }
+        new_pages.push_back(page);
     }
 
     // Now insert the pages
@@ -1269,14 +1264,11 @@ test_35(QPDF& pdf, char const* arg2)
             attachments[filename] = stream.getStreamData();
         }
     }
-    for (std::map<std::string, std::shared_ptr<Buffer>>::iterator iter =
-             attachments.begin();
-         iter != attachments.end();
-         ++iter) {
-        std::string const& filename = (*iter).first;
+    for (auto const& iter: attachments) {
+        std::string const& filename = iter.first;
         std::string data = std::string(
-            reinterpret_cast<char const*>((*iter).second->getBuffer()),
-            (*iter).second->getSize());
+            reinterpret_cast<char const*>(iter.second->getBuffer()),
+            iter.second->getSize());
         bool is_binary = false;
         for (size_t i = 0; i < data.size(); ++i) {
             if ((data.at(i) < 0) || (data.at(i) > 126)) {
@@ -1338,10 +1330,7 @@ test_37(QPDF& pdf, char const* arg2)
     // Parse content streams of all pages
     std::vector<QPDFPageObjectHelper> pages =
         QPDFPageDocumentHelper(pdf).getAllPages();
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter) {
-        QPDFPageObjectHelper& page(*iter);
+    for (auto& page: pages) {
         ParserCallbacks cb;
         page.parseContents(&cb);
     }
@@ -1364,16 +1353,11 @@ test_39(QPDF& pdf, char const* arg2)
     std::vector<QPDFPageObjectHelper> pages =
         QPDFPageDocumentHelper(pdf).getAllPages();
     int pageno = 0;
-    for (std::vector<QPDFPageObjectHelper>::iterator p_iter = pages.begin();
-         p_iter != pages.end();
-         ++p_iter) {
+    for (auto& page: pages) {
         std::cout << "page " << ++pageno << std::endl;
-        std::map<std::string, QPDFObjectHandle> images = (*p_iter).getImages();
-        for (std::map<std::string, QPDFObjectHandle>::iterator i_iter =
-                 images.begin();
-             i_iter != images.end();
-             ++i_iter) {
-            QPDFObjectHandle image_dict = (*i_iter).second.getDict();
+        std::map<std::string, QPDFObjectHandle> images = page.getImages();
+        for (auto& i_iter: images) {
+            QPDFObjectHandle image_dict = i_iter.second.getDict();
             std::cout << "filter: "
                       << image_dict.getKey("/Filter").unparseResolved()
                       << ", color space: "
@@ -1404,10 +1388,8 @@ test_41(QPDF& pdf, char const* arg2)
     // with coalesce.pdf.
     std::vector<QPDFPageObjectHelper> pages =
         QPDFPageDocumentHelper(pdf).getAllPages();
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter) {
-        (*iter).addContentTokenFilter(
+    for (auto& page: pages) {
+        page.addContentTokenFilter(
             std::shared_ptr<QPDFObjectHandle::TokenFilter>(new TokenFilter()));
     }
     QPDFWriter w(pdf, "a.pdf");
@@ -1537,11 +1519,7 @@ test_43(QPDF& pdf, char const* arg2)
     }
     std::cout << "iterating over form fields\n";
     std::vector<QPDFFormFieldObjectHelper> form_fields = afdh.getFormFields();
-    for (std::vector<QPDFFormFieldObjectHelper>::iterator iter =
-             form_fields.begin();
-         iter != form_fields.end();
-         ++iter) {
-        QPDFFormFieldObjectHelper ffh(*iter);
+    for (auto& ffh: form_fields) {
         std::cout << "Field: " << ffh.getObjectHandle().unparse() << std::endl;
         QPDFFormFieldObjectHelper node = ffh;
         while (!node.isNull()) {
@@ -1571,29 +1549,17 @@ test_43(QPDF& pdf, char const* arg2)
         std::cout << "  Quadding: " << ffh.getQuadding() << std::endl;
         std::vector<QPDFAnnotationObjectHelper> annotations =
             afdh.getAnnotationsForField(ffh);
-        for (std::vector<QPDFAnnotationObjectHelper>::iterator i2 =
-                 annotations.begin();
-             i2 != annotations.end();
-             ++i2) {
-            std::cout << "  Annotation: " << (*i2).getObjectHandle().unparse()
+        for (auto& aoh: annotations) {
+            std::cout << "  Annotation: " << aoh.getObjectHandle().unparse()
                       << std::endl;
         }
     }
     std::cout << "iterating over annotations per page\n";
-    std::vector<QPDFPageObjectHelper> pages =
-        QPDFPageDocumentHelper(pdf).getAllPages();
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter) {
-        std::cout << "Page: " << (*iter).getObjectHandle().unparse()
-                  << std::endl;
+    for (auto& page: QPDFPageDocumentHelper(pdf).getAllPages()) {
+        std::cout << "Page: " << page.getObjectHandle().unparse() << std::endl;
         std::vector<QPDFAnnotationObjectHelper> annotations =
-            afdh.getWidgetAnnotationsForPage(*iter);
-        for (std::vector<QPDFAnnotationObjectHelper>::iterator i2 =
-                 annotations.begin();
-             i2 != annotations.end();
-             ++i2) {
-            QPDFAnnotationObjectHelper ah(*i2);
+            afdh.getWidgetAnnotationsForPage(page);
+        for (auto& ah: annotations) {
             std::cout << "  Annotation: " << ah.getObjectHandle().unparse()
                       << std::endl;
             std::cout
@@ -1623,10 +1589,7 @@ test_44(QPDF& pdf, char const* arg2)
     // Set form fields.
     QPDFAcroFormDocumentHelper afdh(pdf);
     std::vector<QPDFFormFieldObjectHelper> fields = afdh.getFormFields();
-    for (std::vector<QPDFFormFieldObjectHelper>::iterator iter = fields.begin();
-         iter != fields.end();
-         ++iter) {
-        QPDFFormFieldObjectHelper& field(*iter);
+    for (auto& field: fields) {
         QPDFObjectHandle ft = field.getInheritableFieldValue("/FT");
         if (ft.isName() && (ft.getName() == "/Tx")) {
             // \xc3\xb7 is utf-8 for U+00F7 (divided by)
@@ -1950,23 +1913,16 @@ static void
 test_49(QPDF& pdf, char const* arg2)
 {
     // Outlines
-    std::vector<QPDFPageObjectHelper> pages =
-        QPDFPageDocumentHelper(pdf).getAllPages();
     QPDFOutlineDocumentHelper odh(pdf);
     int pageno = 0;
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter, ++pageno) {
-        std::vector<QPDFOutlineObjectHelper> outlines =
-            odh.getOutlinesForPage((*iter).getObjectHandle().getObjGen());
-        for (std::vector<QPDFOutlineObjectHelper>::iterator oiter =
-                 outlines.begin();
-             oiter != outlines.end();
-             ++oiter) {
-            std::cout << "page " << pageno << ": " << (*oiter).getTitle()
-                      << " -> " << (*oiter).getDest().unparseResolved()
-                      << std::endl;
+    for (auto& page: QPDFPageDocumentHelper(pdf).getAllPages()) {
+        auto outlines =
+            odh.getOutlinesForPage(page.getObjectHandle().getObjGen());
+        for (auto& ol: outlines) {
+            std::cout << "page " << pageno << ": " << ol.getTitle() << " -> "
+                      << ol.getDest().unparseResolved() << std::endl;
         }
+        ++pageno;
     }
 }
 
@@ -1981,11 +1937,8 @@ test_50(QPDF& pdf, char const* arg2)
     std::cout << d1.getJSON().unparse() << std::endl;
     // Top-level type mismatch
     d1.mergeResources(d2.getKey("/k1"));
-    std::set<std::string> names = d1.getResourceNames();
-    for (std::set<std::string>::iterator iter = names.begin();
-         iter != names.end();
-         ++iter) {
-        std::cout << *iter << std::endl;
+    for (auto const& name: d1.getResourceNames()) {
+        std::cout << name << std::endl;
     }
 }
 
@@ -2064,11 +2017,8 @@ test_53(QPDF& pdf, char const* arg2)
     root.replaceKey(
         "/Q1", pdf.makeIndirectObject(QPDFObjectHandle::newString("potato")));
     std::cout << "all objects" << std::endl;
-    std::vector<QPDFObjectHandle> all = pdf.getAllObjects();
-    for (std::vector<QPDFObjectHandle>::iterator iter = all.begin();
-         iter != all.end();
-         ++iter) {
-        std::cout << (*iter).unparse() << std::endl;
+    for (auto& obj: pdf.getAllObjects()) {
+        std::cout << obj.unparse() << std::endl;
     }
 
     QPDFWriter w(pdf, "a.pdf");
diff --git a/qpdf/test_parsedoffset.cc b/qpdf/test_parsedoffset.cc
index aecaf404..26a50875 100644
--- a/qpdf/test_parsedoffset.cc
+++ b/qpdf/test_parsedoffset.cc
@@ -52,21 +52,17 @@ walk(
 
     if (obj.isArray()) {
         std::vector<QPDFObjectHandle> array = obj.getArrayAsVector();
-        for (std::vector<QPDFObjectHandle>::iterator iter = array.begin();
-             iter != array.end();
-             ++iter) {
-            if (!iter->isIndirect()) {
+        for (auto& oh: array) {
+            if (!oh.isIndirect()) {
                 // QPDF::GetAllObjects() enumerates all indirect objects.
                 // So only the direct objects are recursed here.
-                walk(stream_number, *iter, result);
+                walk(stream_number, oh, result);
             }
         }
     } else if (obj.isDictionary()) {
         std::set<std::string> keys = obj.getKeys();
-        for (std::set<std::string>::iterator iter = keys.begin();
-             iter != keys.end();
-             ++iter) {
-            QPDFObjectHandle item = obj.getKey(*iter);
+        for (auto const& key: keys) {
+            QPDFObjectHandle item = obj.getKey(key);
             if (!item.isIndirect()) {
                 // QPDF::GetAllObjects() enumerates all indirect objects.
                 // So only the direct objects are recursed here.
@@ -88,21 +84,19 @@ process(
     std::vector<QPDFObjectHandle> objs = qpdf.getAllObjects();
     std::map<QPDFObjGen, QPDFXRefEntry> xrefs = qpdf.getXRefTable();
 
-    for (std::vector<QPDFObjectHandle>::iterator iter = objs.begin();
-         iter != objs.end();
-         ++iter) {
-        if (xrefs.count(iter->getObjGen()) == 0) {
-            std::cerr << iter->getObjectID() << "/" << iter->getGeneration()
+    for (auto const& oh: objs) {
+        if (xrefs.count(oh.getObjGen()) == 0) {
+            std::cerr << oh.getObjectID() << "/" << oh.getGeneration()
                       << " is not found in xref table" << std::endl;
             std::exit(2);
         }
 
-        QPDFXRefEntry xref = xrefs[iter->getObjGen()];
+        QPDFXRefEntry xref = xrefs[oh.getObjGen()];
         size_t stream_number;
 
         switch (xref.getType()) {
         case 0:
-            std::cerr << iter->getObjectID() << "/" << iter->getGeneration()
+            std::cerr << oh.getObjectID() << "/" << oh.getGeneration()
                       << " xref entry is free" << std::endl;
             std::exit(2);
         case 1:
@@ -116,7 +110,7 @@ process(
             std::exit(2);
         }
 
-        walk(stream_number, *iter, result);
+        walk(stream_number, oh, result);
     }
 }
 
@@ -146,11 +140,8 @@ main(int argc, char* argv[])
                           << std::endl;
             }
 
-            for (std::vector<std::pair<qpdf_offset_t, std::string>>::iterator
-                     iter = table[i].begin();
-                 iter != table[i].end();
-                 ++iter) {
-                std::cout << iter->second << std::endl;
+            for (auto const& iter: table[i]) {
+                std::cout << iter.second << std::endl;
             }
         }
 
diff --git a/qpdf/test_pdf_doc_encoding.cc b/qpdf/test_pdf_doc_encoding.cc
index 3dafceac..c705fd2f 100644
--- a/qpdf/test_pdf_doc_encoding.cc
+++ b/qpdf/test_pdf_doc_encoding.cc
@@ -27,10 +27,8 @@ main(int argc, char* argv[])
     }
     char const* infilename = argv[1];
     std::list<std::string> lines = QUtil::read_lines_from_file(infilename);
-    for (std::list<std::string>::iterator iter = lines.begin();
-         iter != lines.end();
-         ++iter) {
-        QPDFObjectHandle str = QPDFObjectHandle::newString(*iter);
+    for (auto const& line: lines) {
+        QPDFObjectHandle str = QPDFObjectHandle::newString(line);
         std::cout << str.getUTF8Value() << std::endl;
     }
     return 0;
diff --git a/qpdf/test_pdf_unicode.cc b/qpdf/test_pdf_unicode.cc
index ead143b3..006b1183 100644
--- a/qpdf/test_pdf_unicode.cc
+++ b/qpdf/test_pdf_unicode.cc
@@ -27,10 +27,8 @@ main(int argc, char* argv[])
     }
     char const* infilename = argv[1];
     std::list<std::string> lines = QUtil::read_lines_from_file(infilename);
-    for (std::list<std::string>::iterator iter = lines.begin();
-         iter != lines.end();
-         ++iter) {
-        QPDFObjectHandle str = QPDFObjectHandle::newUnicodeString(*iter);
+    for (auto const& line: lines) {
+        QPDFObjectHandle str = QPDFObjectHandle::newUnicodeString(line);
         std::cout << str.getUTF8Value() << " // " << str.unparseBinary()
                   << std::endl;
     }
diff --git a/qpdf/test_renumber.cc b/qpdf/test_renumber.cc
index da4d7c1d..206ef49a 100644
--- a/qpdf/test_renumber.cc
+++ b/qpdf/test_renumber.cc
@@ -97,10 +97,8 @@ compare(QPDFObjectHandle a, QPDFObjectHandle b)
                 return false;
             }
 
-            for (std::set<std::string>::iterator iter = keys_a.begin();
-                 iter != keys_a.end();
-                 ++iter) {
-                if (!compare(a.getKey(*iter), b.getKey(*iter))) {
+            for (auto const& key: keys_a) {
+                if (!compare(a.getKey(key), b.getKey(key))) {
                     std::cerr << "different dictionary item" << std::endl;
                     return false;
                 }
@@ -130,19 +128,17 @@ compare_xref_table(
         return false;
     }
 
-    for (std::map<QPDFObjGen, QPDFXRefEntry>::iterator iter = a.begin();
-         iter != a.end();
-         ++iter) {
-        std::cout << "xref entry for " << iter->first.getObj() << "/"
-                  << iter->first.getGen() << std::endl;
+    for (auto const& iter: a) {
+        std::cout << "xref entry for " << iter.first.getObj() << "/"
+                  << iter.first.getGen() << std::endl;
 
-        if (b.count(iter->first) == 0) {
+        if (b.count(iter.first) == 0) {
             std::cerr << "not found" << std::endl;
             return false;
         }
 
-        QPDFXRefEntry xref_a = iter->second;
-        QPDFXRefEntry xref_b = b[iter->first];
+        QPDFXRefEntry xref_a = iter.second;
+        QPDFXRefEntry xref_b = b[iter.first];
         if (xref_a.getType() != xref_b.getType()) {
             std::cerr << "different xref entry type" << std::endl;
             return false;
@@ -235,10 +231,8 @@ main(int argc, char* argv[])
 
         std::cout << "--- compare between input and renumbered objects ---"
                   << std::endl;
-        for (std::vector<QPDFObjectHandle>::iterator iter = objs_in.begin();
-             iter != objs_in.end();
-             ++iter) {
-            QPDFObjGen og_in = iter->getObjGen();
+        for (auto const& iter: objs_in) {
+            QPDFObjGen og_in = iter.getObjGen();
             QPDFObjGen og_ren = w.getRenumberedObjGen(og_in);
 
             std::cout << "input " << og_in.getObj() << "/" << og_in.getGen()
@@ -250,7 +244,7 @@ main(int argc, char* argv[])
                 continue;
             }
 
-            if (!compare(*iter, qpdf_ren.getObjectByObjGen(og_ren))) {
+            if (!compare(iter, qpdf_ren.getObjectByObjGen(og_ren))) {
                 std::cerr << "different" << std::endl;
                 std::exit(2);
             }
diff --git a/qpdf/test_tokenizer.cc b/qpdf/test_tokenizer.cc
index c3cda112..f1155a28 100644
--- a/qpdf/test_tokenizer.cc
+++ b/qpdf/test_tokenizer.cc
@@ -99,14 +99,13 @@ static std::string
 sanitize(std::string const& value)
 {
     std::string result;
-    for (std::string::const_iterator iter = value.begin(); iter != value.end();
-         ++iter) {
-        if ((*iter >= 32) && (*iter <= 126)) {
-            result.append(1, *iter);
+    for (auto const& iter: value) {
+        if ((iter >= 32) && (iter <= 126)) {
+            result.append(1, iter);
         } else {
             result += "\\x" +
                 QUtil::int_to_string_base(
-                          static_cast<unsigned char>(*iter), 16, 2);
+                          static_cast<unsigned char>(iter), 16, 2);
         }
     }
     return result;
@@ -203,12 +202,10 @@ process(char const* filename, bool include_ignorable, size_t max_len)
     std::vector<QPDFPageObjectHelper> pages =
         QPDFPageDocumentHelper(qpdf).getAllPages();
     int pageno = 0;
-    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
-         iter != pages.end();
-         ++iter) {
+    for (auto& page: pages) {
         ++pageno;
         Pl_Buffer plb("buffer");
-        (*iter).pipeContents(&plb);
+        page.pipeContents(&plb);
         auto content_data = plb.getBufferSharedPointer();
         BufferInputSource* bis =
             new BufferInputSource("content data", content_data.get());
@@ -223,20 +220,16 @@ process(char const* filename, bool include_ignorable, size_t max_len)
     }
 
     // Tokenize object streams
-    std::vector<QPDFObjectHandle> all = qpdf.getAllObjects();
-    for (std::vector<QPDFObjectHandle>::iterator iter = all.begin();
-         iter != all.end();
-         ++iter) {
-        if ((*iter).isStream() && (*iter).getDict().getKey("/Type").isName() &&
-            (*iter).getDict().getKey("/Type").getName() == "/ObjStm") {
-            std::shared_ptr<Buffer> b =
-                (*iter).getStreamData(qpdf_dl_specialized);
+    for (auto& obj: qpdf.getAllObjects()) {
+        if (obj.isStream() && obj.getDict().getKey("/Type").isName() &&
+            obj.getDict().getKey("/Type").getName() == "/ObjStm") {
+            std::shared_ptr<Buffer> b = obj.getStreamData(qpdf_dl_specialized);
             BufferInputSource* bis =
                 new BufferInputSource("object stream data", b.get());
             is = std::shared_ptr<InputSource>(bis);
             dump_tokens(
                 is,
-                "OBJECT STREAM " + QUtil::int_to_string((*iter).getObjectID()),
+                "OBJECT STREAM " + QUtil::int_to_string(obj.getObjectID()),
                 max_len,
                 include_ignorable,
                 false,
diff --git a/qpdf/test_xref.cc b/qpdf/test_xref.cc
index 238ef2a0..2c89dce7 100644
--- a/qpdf/test_xref.cc
+++ b/qpdf/test_xref.cc
@@ -21,26 +21,24 @@ main(int argc, char* argv[])
 
         std::map<QPDFObjGen, QPDFXRefEntry> xref = qpdf.getXRefTable();
 
-        for (std::map<QPDFObjGen, QPDFXRefEntry>::iterator iter = xref.begin();
-             iter != xref.end();
-             ++iter) {
-            std::cout << iter->first.getObj() << "/" << iter->first.getGen()
+        for (auto const& iter: xref) {
+            std::cout << iter.first.getObj() << "/" << iter.first.getGen()
                       << ", ";
-            switch (iter->second.getType()) {
+            switch (iter.second.getType()) {
             case 0:
                 std::cout << "free entry" << std::endl;
                 break;
             case 1:
                 std::cout << "uncompressed, offset = "
-                          << iter->second.getOffset() << " (0x" << std::hex
-                          << iter->second.getOffset() << std::dec << ")"
+                          << iter.second.getOffset() << " (0x" << std::hex
+                          << iter.second.getOffset() << std::dec << ")"
                           << std::endl;
                 break;
             case 2:
                 std::cout << "compressed, stream number = "
-                          << iter->second.getObjStreamNumber()
+                          << iter.second.getObjStreamNumber()
                           << ", stream index = "
-                          << iter->second.getObjStreamIndex() << std::endl;
+                          << iter.second.getObjStreamIndex() << std::endl;
                 break;
             default:
                 std::cerr << "unknown" << std::endl;