Object, COFF: Infer symbol sizes from adjacent symbols

Use the position of the subsequent symbol in the object file to infer
the size of it's predecessor.  I hope to eventually remove whatever COFF
specific details from this little algorithm so that we can unify this
logic with what Mach-O does.

llvm-svn: 221444

1 files changed, 39 insertions, 7 deletions

diff --git a/llvm/lib/Object/COFFObjectFile.cpp b/llvm/lib/Object/COFFObjectFile.cpp
index 4fbb78254ea..7a0892dd98d 100644
--- a/llvm/lib/Object/COFFObjectFile.cpp
+++ b/llvm/lib/Object/COFFObjectFile.cpp
@@ -250,20 +250,52 @@ std::error_code COFFObjectFile::getSymbolSize(DataRefImpl Ref,
       return object_error::success;
     }
   }
-  // FIXME: Return the correct size. This requires looking at all the symbols
-  //        in the same section as this symbol, and looking for either the next
-  //        symbol, or the end of the section.
+
+  // Let's attempt to get the size of the symbol by looking at the address of
+  // the symbol after the symbol in question.
+  uint64_t SymbAddr;
+  if (std::error_code EC = getSymbolAddress(Ref, SymbAddr))
+    return EC;
   int32_t SectionNumber = Symb.getSectionNumber();
-  if (!COFF::isReservedSectionNumber(SectionNumber)) {
+  if (COFF::isReservedSectionNumber(SectionNumber)) {
+    // Absolute and debug symbols aren't sorted in any interesting way.
+    Result = 0;
+    return object_error::success;
+  }
+  const section_iterator SecEnd = section_end();
+  uint64_t AfterAddr = UnknownAddressOrSize;
+  for (const symbol_iterator &SymbI : symbols()) {
+    section_iterator SecI = SecEnd;
+    if (std::error_code EC = SymbI->getSection(SecI))
+      return EC;
+    // Check the symbol's section, skip it if it's in the wrong section.
+    // First, make sure it is in any section.
+    if (SecI == SecEnd)
+      continue;
+    // Second, make sure it is in the same section as the symbol in question.
+    if (!sectionContainsSymbol(SecI->getRawDataRefImpl(), Ref))
+      continue;
+    uint64_t Addr;
+    if (std::error_code EC = SymbI->getAddress(Addr))
+      return EC;
+    // We want to compare our symbol in question with the closest possible
+    // symbol that comes after.
+    if (AfterAddr > Addr && Addr > SymbAddr)
+      AfterAddr = Addr;
+  }
+  if (AfterAddr == UnknownAddressOrSize) {
+    // No symbol comes after this one, assume that everything after our symbol
+    // is part of it.
     const coff_section *Section = nullptr;
     if (std::error_code EC = getSection(SectionNumber, Section))
       return EC;
-
     Result = Section->SizeOfRawData - Symb.getValue();
-    return object_error::success;
+  } else {
+    // Take the difference between our symbol and the symbol that comes after
+    // our symbol.
+    Result = AfterAddr - SymbAddr;
   }
 
-  Result = 0;
   return object_error::success;
 }