[mach-o] don't assume all sections have symbols

We were trying to examine the first symbol in a section that we wanted to
atomize by symbols, even when there wasn't one. Instead, we should make the
initial anonymous symbol cover the entire section in that situation.

llvm-svn: 211681

1 files changed, 6 insertions, 4 deletions

diff --git a/lld/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp b/lld/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp
index 2be8d3b2db0..7de85e87603 100644
--- a/lld/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp
+++ b/lld/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp
@@ -284,11 +284,13 @@ std::error_code processSymboledSection(DefinedAtom::ContentType atomType,
   if (symbols.empty() && section.content.empty())
     return std::error_code();
 
-  const uint64_t firstSymbolAddr = symbols.front()->value;
-  if (firstSymbolAddr != section.address) {
+  uint64_t anonAtomEnd = symbols.empty()
+                             ? section.address + section.content.size()
+                             : (uint64_t)symbols.front()->value;
+  if (anonAtomEnd != section.address) {
     // Section has anonymous content before first symbol.
-    atomFromSymbol(atomType, section, file, section.address, StringRef(),
-                  0, Atom::scopeTranslationUnit, firstSymbolAddr, copyRefs);
+    atomFromSymbol(atomType, section, file, section.address, StringRef(), 0,
+                   Atom::scopeTranslationUnit, anonAtomEnd, copyRefs);
   }
 
   const Symbol *lastSym = nullptr;