Fix sign and conversion warnings (major)

This makes all integer type conversions that have potential data loss
explicit with calls that do range checks and raise an exception. After
this commit, qpdf builds with no warnings when -Wsign-conversion
-Wconversion is used with gcc or clang or when -W3 -Wd4800 is used
with MSVC. This significantly reduces the likelihood of potential
crashes from bogus integer values.

There are some parts of the code that take int when they should take
size_t or an offset. Such places would make qpdf not support files
with more than 2^31 of something that usually wouldn't be so large. In
the event that such a file shows up and is valid, at least qpdf would
raise an error in the right spot so the issue could be legitimately
addressed rather than failing in some weird way because of a silent
overflow condition.

5 files changed, 27 insertions, 21 deletions

diff --git a/examples/pdf-create.cc b/examples/pdf-create.cc
index 1c787e2e..b27d4e17 100644
--- a/examples/pdf-create.cc
+++ b/examples/pdf-create.cc
@@ -14,6 +14,7 @@
 #include <qpdf/Pl_Buffer.hh>
 #include <qpdf/Pl_RunLength.hh>
 #include <qpdf/Pl_DCT.hh>
+#include <qpdf/QIntC.hh>
 #include <iostream>
 #include <string.h>
 #include <stdlib.h>
@@ -30,15 +31,15 @@ class ImageProvider: public QPDFObjectHandle::StreamDataProvider
     virtual ~ImageProvider();
     virtual void provideStreamData(int objid, int generation,
 				   Pipeline* pipeline);
-    int getWidth() const;
-    int getHeight() const;
+    size_t getWidth() const;
+    size_t getHeight() const;
 
   private:
-    int width;
-    int stripe_height;
+    size_t width;
+    size_t stripe_height;
     std::string color_space;
     std::string filter;
-    int n_stripes;
+    size_t n_stripes;
     std::vector<std::string> stripes;
     J_COLOR_SPACE j_color_space;
 };
@@ -88,13 +89,13 @@ ImageProvider::~ImageProvider()
 {
 }
 
-int
+size_t
 ImageProvider::getWidth() const
 {
     return width;
 }
 
-int
+size_t
 ImageProvider::getHeight() const
 {
     return stripe_height * n_stripes;
@@ -111,7 +112,8 @@ ImageProvider::provideStreamData(int objid, int generation,
     {
         p = new Pl_DCT(
             "image encoder", pipeline,
-            width, getHeight(), stripes[0].length(), j_color_space);
+            QIntC::to_uint(width), QIntC::to_uint(getHeight()),
+            QIntC::to_int(stripes[0].length()), j_color_space);
         to_delete.push_back(p);
     }
     else if (filter == "/RunLengthDecode")
@@ -121,9 +123,9 @@ ImageProvider::provideStreamData(int objid, int generation,
         to_delete.push_back(p);
     }
 
-    for (int i = 0; i < n_stripes; ++i)
+    for (size_t i = 0; i < n_stripes; ++i)
     {
-        for (int j = 0; j < width * stripe_height; ++j)
+        for (size_t j = 0; j < width * stripe_height; ++j)
         {
             p->write(
                 QUtil::unsigned_char_pointer(stripes[i].c_str()),
@@ -155,9 +157,9 @@ QPDFObjectHandle newName(std::string const& name)
     return QPDFObjectHandle::newName(name);
 }
 
-QPDFObjectHandle newInteger(int val)
+QPDFObjectHandle newInteger(size_t val)
 {
-    return QPDFObjectHandle::newInteger(val);
+    return QPDFObjectHandle::newInteger(QIntC::to_int(val));
 }
 
 void add_page(QPDFPageDocumentHelper& dh, QPDFObjectHandle font,
@@ -173,8 +175,8 @@ void add_page(QPDFPageDocumentHelper& dh, QPDFObjectHandle font,
     // compression.
     ImageProvider* p = new ImageProvider(color_space, filter);
     PointerHolder<QPDFObjectHandle::StreamDataProvider> provider(p);
-    int width = p->getWidth();
-    int height = p->getHeight();
+    size_t width = p->getWidth();
+    size_t height = p->getHeight();
     QPDFObjectHandle image = QPDFObjectHandle::newStream(&pdf);
     image.replaceDict(QPDFObjectHandle::parse(
                           "<<"
@@ -335,8 +337,8 @@ static void check(char const* filename,
                 unsigned int mismatches = 0;
                 int tolerance = (
                     desired_filter == "/DCTDecode" ? 10 : 0);
-                unsigned int threshold = (
-                    desired_filter == "/DCTDecode" ? len / 40 : 0);
+                size_t threshold = (
+                    desired_filter == "/DCTDecode" ? len / 40U : 0);
                 for (size_t i = 0; i < len; ++i)
                 {
                     int delta = actual_bytes[i] - desired_bytes[i];
diff --git a/examples/pdf-double-page-size.cc b/examples/pdf-double-page-size.cc
index 06c98921..6c5e5913 100644
--- a/examples/pdf-double-page-size.cc
+++ b/examples/pdf-double-page-size.cc
@@ -34,7 +34,7 @@ static void doubleBoxSize(QPDFObjectHandle& page, char const* box_name)
 				 " is not an array of four elements");
     }
     std::vector<QPDFObjectHandle> doubled;
-    for (unsigned int i = 0; i < 4; ++i)
+    for (int i = 0; i < 4; ++i)
     {
 	doubled.push_back(
 	    QPDFObjectHandle::newReal(
diff --git a/examples/pdf-invert-images.cc b/examples/pdf-invert-images.cc
index 1469d9cc..a149c495 100644
--- a/examples/pdf-invert-images.cc
+++ b/examples/pdf-invert-images.cc
@@ -7,6 +7,7 @@
 #include <qpdf/QUtil.hh>
 #include <qpdf/Buffer.hh>
 #include <qpdf/QPDFWriter.hh>
+#include <qpdf/QIntC.hh>
 
 static char const* whoami = 0;
 
@@ -56,7 +57,7 @@ ImageInverter::provideStreamData(int objid, int generation,
     unsigned char ch;
     for (size_t i = 0; i < size; ++i)
     {
-	ch = static_cast<unsigned char>(0xff) - buf[i];
+	ch = QIntC::to_uchar(0xff - buf[i]);
 	pipeline->write(&ch, 1);
     }
     pipeline->finish();
diff --git a/examples/pdf-parse-content.cc b/examples/pdf-parse-content.cc
index 8659fbe3..254fcdfe 100644
--- a/examples/pdf-parse-content.cc
+++ b/examples/pdf-parse-content.cc
@@ -6,6 +6,7 @@
 #include <qpdf/QPDFPageDocumentHelper.hh>
 #include <qpdf/QPDFPageObjectHelper.hh>
 #include <qpdf/QUtil.hh>
+#include <qpdf/QIntC.hh>
 
 static char const* whoami = 0;
 
@@ -72,12 +73,12 @@ int main(int argc, char* argv[])
 	pdf.processFile(filename);
         std::vector<QPDFPageObjectHelper> pages =
             QPDFPageDocumentHelper(pdf).getAllPages();
-        if ((pageno < 1) || (static_cast<size_t>(pageno) > pages.size()))
+        if ((pageno < 1) || (QIntC::to_size(pageno) > pages.size()))
         {
             usage();
         }
 
-        QPDFPageObjectHelper& page = pages.at(pageno-1);
+        QPDFPageObjectHelper& page = pages.at(QIntC::to_size(pageno-1));
         ParserCallbacks cb;
         page.parsePageContents(&cb);
     }
diff --git a/examples/pdf-split-pages.cc b/examples/pdf-split-pages.cc
index b6dd701b..7857d649 100644
--- a/examples/pdf-split-pages.cc
+++ b/examples/pdf-split-pages.cc
@@ -8,6 +8,7 @@
 #include <qpdf/QPDFPageDocumentHelper.hh>
 #include <qpdf/QPDFWriter.hh>
 #include <qpdf/QUtil.hh>
+#include <qpdf/QIntC.hh>
 
 #include <iostream>
 #include <stdlib.h>
@@ -24,7 +25,8 @@ static void process(char const* whoami,
     inpdf.processFile(infile);
     std::vector<QPDFPageObjectHelper> pages =
         QPDFPageDocumentHelper(inpdf).getAllPages();
-    int pageno_len = QUtil::int_to_string(pages.size()).length();
+    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)