Object/COFF: Fix getSectionSize

[ruiu]

Summary

Some tools such as yasm set a bogus value to object file's
VirtualSize field, so we cannot trust this field. This patch
determines if it's an object or an executable by checking
existence of PE header.

[majnemer]

LGTM with review comments addressed.

lib/Object/COFFObjectFile.cpp

920

I would add a comment saying that VirtualSize should be zero for object files but isn't due to buggy COFF writers.

925

You could reuse the existing logic by making this if (getDOSHeader()).

lib/Object/COFFObjectFile.cpp

std::error_code COFFObjectFile::getSectionName(const coff_section *Sec,
   Res = Name;
   return std::error_code();
 }
 
 uint64_t COFFObjectFile::getSectionSize(const coff_section *Sec) const {
   // SizeOfRawData and VirtualSize change what they represent depending on
   // whether or not we have an executable image.
   //
-  // For object files, SizeOfRawData contains the size of section's data;
-  // VirtualSize is always zero.
-  //
+  // For object files, SizeOfRawData contains the size of section's data.
   // For executables, SizeOfRawData *must* be a multiple of FileAlignment; the
   // actual section size is in VirtualSize.  It is possible for VirtualSize to
   // be greater than SizeOfRawData; the contents past that point should be
   // considered to be zero.
-  uint32_t SectionSize;
-  if (Sec->VirtualSize)
-    SectionSize = std::min(Sec->VirtualSize, Sec->SizeOfRawData);
-  else
-    SectionSize = Sec->SizeOfRawData;
-
-  return SectionSize;
+  if (PE32Header || PE32PlusHeader)
+    return std::min(Sec->VirtualSize, Sec->SizeOfRawData);
+  return Sec->SizeOfRawData;
 }
 
 std::error_code
 COFFObjectFile::getSectionContents(const coff_section *Sec,
                                    ArrayRef<uint8_t> &Res) const {
   // PointerToRawData and SizeOfRawData won't make sense for BSS sections,
   // don't do anything interesting for them.
   assert((Sec->Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 &&