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. :-)

15 files changed, 254 insertions, 585 deletions

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;