[llvm-objdump] Replace array_pod_sort with llvm::stable_sort

[MaskRay]

Summary

llvm-objdump.test has 3 array_pod_sort() used for symbolization.
array_pod_start() calls qsort() internally and can have different
behaviors across different libcs. Use llvm::stable_sort instead.

[thopre]

LGTM. This is what I think is causing tools/llvm-objdump/X86/disassemble-functions.test to fail in some settings (see my comment https://reviews.llvm.org/D75631#1940245)

llvm/tools/llvm-objdump/llvm-objdump.cpp

1205–1207

Also non allocatable sections have 0 for start address. Dunno if it's worth mentioning.

[davidb]

Thanks for this!

[davidb]

llvm/tools/llvm-objdump/llvm-objdump.cpp

1205–1207

Might be worth considering this as a future change. I think excluding sections that do not have SHF_ALLOC could cause issues in some cases where one might forget to set the appropriate section flags in assembly.

[jhenderson]

llvm/tools/llvm-objdump/llvm-objdump.cpp

1207

Here and below: stabalize -> stabilize.

[MaskRay]

llvm/tools/llvm-objdump/llvm-objdump.cpp

1207

Thanks! Fixed by 579a7a1938403c272706e91fe6c9367ff682eea1

llvm/tools/llvm-objdump/llvm-objdump.cpp

static void disassembleObject(const Target *TheTarget, const ObjectFile *Obj,
   }
   if (AllSymbols.empty() && Obj->isELF())
     addDynamicElfSymbols(Obj, AllSymbols);
 
   BumpPtrAllocator A;
   StringSaver Saver(A);
   addPltEntries(Obj, AllSymbols, Saver);
 
-  // Create a mapping from virtual address to section.
+  // Create a mapping from virtual address to section. An empty section can
+  // cause more than one section at the same address. Use a stable sort to
+  // stabalize the output.
   std::vector<std::pair<uint64_t, SectionRef>> SectionAddresses;
   for (SectionRef Sec : Obj->sections())
     SectionAddresses.emplace_back(Sec.getAddress(), Sec);
-  array_pod_sort(SectionAddresses.begin(), SectionAddresses.end());
+  stable_sort(SectionAddresses);
 
   // Linked executables (.exe and .dll files) typically don't include a real
   // symbol table but they might contain an export table.
   if (const auto *COFFObj = dyn_cast<COFFObjectFile>(Obj)) {
     for (const auto &ExportEntry : COFFObj->export_directories()) {
       StringRef Name;
       if (std::error_code EC = ExportEntry.getSymbolName(Name))
         reportError(errorCodeToError(EC), Obj->getFileName());
for (const auto &ExportEntry : COFFObj->export_directories()) {
         --Sec;
         AllSymbols[Sec->second].emplace_back(VA, Name, ELF::STT_NOTYPE);
       } else
         AbsoluteSymbols.emplace_back(VA, Name, ELF::STT_NOTYPE);
     }
   }
 
   // Sort all the symbols, this allows us to use a simple binary search to find
-  // a symbol near an address.
+  // Multiple symbols can have the same address. Use a stable sort to stabalize
+  // the output.
   StringSet<> FoundDisasmSymbolSet;
   for (std::pair<const SectionRef, SectionSymbolsTy> &SecSyms : AllSymbols)
-    array_pod_sort(SecSyms.second.begin(), SecSyms.second.end());
-  array_pod_sort(AbsoluteSymbols.begin(), AbsoluteSymbols.end());
+    stable_sort(SecSyms.second);
+  stable_sort(AbsoluteSymbols);
 
   for (const SectionRef &Section : ToolSectionFilter(*Obj)) {
     if (FilterSections.empty() && !DisassembleAll &&
         (!Section.isText() || Section.isVirtual()))
       continue;
 
     uint64_t SectionAddr = Section.getAddress();
     uint64_t SectSize = Section.getSize();