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.

1 files changed, 20 insertions, 14 deletions

diff --git a/libqpdf/QPDFFormFieldObjectHelper.cc b/libqpdf/QPDFFormFieldObjectHelper.cc
index 08042df2..b3c61ce5 100644
--- a/libqpdf/QPDFFormFieldObjectHelper.cc
+++ b/libqpdf/QPDFFormFieldObjectHelper.cc
@@ -4,6 +4,7 @@
 #include <qpdf/QPDFAnnotationObjectHelper.hh>
 #include <qpdf/QUtil.hh>
 #include <qpdf/Pl_QPDFTokenizer.hh>
+#include <qpdf/QIntC.hh>
 #include <stdlib.h>
 
 QPDFFormFieldObjectHelper::Members::~Members()
@@ -189,7 +190,7 @@ QPDFFormFieldObjectHelper::getQuadding()
     if (fv.isInteger())
     {
         QTC::TC("qpdf", "QPDFFormFieldObjectHelper Q present");
-        result = static_cast<int>(fv.getIntValue());
+        result = QIntC::to_int(fv.getIntValue());
     }
     return result;
 }
@@ -198,7 +199,7 @@ int
 QPDFFormFieldObjectHelper::getFlags()
 {
     QPDFObjectHandle f = getInheritableFieldValue("/Ff");
-    return f.isInteger() ? f.getIntValue() : 0;
+    return f.isInteger() ? f.getIntValueAsInt() : 0;
 }
 
 bool
@@ -245,8 +246,8 @@ QPDFFormFieldObjectHelper::getChoices()
     QPDFObjectHandle opt = getInheritableFieldValue("/Opt");
     if (opt.isArray())
     {
-        size_t n = opt.getArrayNItems();
-        for (size_t i = 0; i < n; ++i)
+        int n = opt.getArrayNItems();
+        for (int i = 0; i < n; ++i)
         {
             QPDFObjectHandle item = opt.getArrayItem(i);
             if (item.isString())
@@ -631,8 +632,8 @@ ValueSetter::writeAppearance()
         {
             // Try to make the found item the second one, but
             // adjust for under/overflow.
-            int wanted_first = found_idx - 1;
-            int wanted_last = found_idx + max_rows - 2;
+            int wanted_first = QIntC::to_int(found_idx) - 1;
+            int wanted_last = QIntC::to_int(found_idx + max_rows) - 2;
             QTC::TC("qpdf", "QPDFFormFieldObjectHelper list found");
             while (wanted_first < 0)
             {
@@ -640,7 +641,7 @@ ValueSetter::writeAppearance()
                 ++wanted_first;
                 ++wanted_last;
             }
-            while (wanted_last >= static_cast<int>(nopt))
+            while (wanted_last >= QIntC::to_int(nopt))
             {
                 QTC::TC("qpdf", "QPDFFormFieldObjectHelper list last too high");
                 if (wanted_first > 0)
@@ -650,8 +651,9 @@ ValueSetter::writeAppearance()
                 --wanted_last;
             }
             highlight = true;
-            highlight_idx = found_idx - wanted_first;
-            for (int i = wanted_first; i <= wanted_last; ++i)
+            highlight_idx = found_idx - QIntC::to_size(wanted_first);
+            for (size_t i = QIntC::to_size(wanted_first);
+                 i <= QIntC::to_size(wanted_last); ++i)
             {
                 lines.push_back(opt.at(i));
             }
@@ -672,13 +674,15 @@ ValueSetter::writeAppearance()
 
     // Write the lines centered vertically, highlighting if needed
     size_t nlines = lines.size();
-    double dy = bbox.ury - ((bbox.ury - bbox.lly - (nlines * tfh)) / 2.0);
+    double dy = bbox.ury - ((bbox.ury - bbox.lly -
+                             (static_cast<double>(nlines) * tfh)) / 2.0);
     if (highlight)
     {
         write("q\n0.85 0.85 0.85 rg\n" +
               QUtil::double_to_string(bbox.llx) + " " +
-              QUtil::double_to_string(bbox.lly + dy -
-                                      (tfh * (highlight_idx + 1))) + " " +
+              QUtil::double_to_string(
+                  bbox.lly + dy -
+                  (tfh * (static_cast<double>(highlight_idx + 1)))) + " " +
               QUtil::double_to_string(bbox.urx - bbox.llx) + " " +
               QUtil::double_to_string(tfh) +
               " re f\nQ\n");
@@ -693,8 +697,10 @@ ValueSetter::writeAppearance()
         // which doesn't seem really worth the effort.
         if (i == 0)
         {
-            write(QUtil::double_to_string(bbox.llx + dx) + " " +
-                  QUtil::double_to_string(bbox.lly + dy) + " Td\n");
+            write(QUtil::double_to_string(bbox.llx + static_cast<double>(dx)) +
+                  " " +
+                  QUtil::double_to_string(bbox.lly + static_cast<double>(dy)) +
+                  " Td\n");
         }
         else
         {