[PATCH] D47976: [ELF] Fix copy relocation when two symbols share the same address.

[Fangrui Song via Phabricator via llvm-commits]

MaskRay updated this revision to Diff 150611.
MaskRay added a comment.

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Repository:
  rLLD LLVM Linker

https://reviews.llvm.org/D47976

Files:
  ELF/Relocations.cpp


Index: ELF/Relocations.cpp
===================================================================
--- ELF/Relocations.cpp
+++ ELF/Relocations.cpp
@@ -52,6 +52,7 @@
 #include "Thunks.h"
 #include "lld/Common/Memory.h"
 #include "lld/Common/Strings.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
@@ -444,21 +445,25 @@
 // If two or more symbols are at the same offset, and at least one of
 // them are copied by a copy relocation, all of them need to be copied.
 // Otherwise, they would refer different places at runtime.
+// Use a set so that if two or more symbols share the same address, we only copy
+// one but with the largest size.
 template <class ELFT>
-static std::vector<SharedSymbol *> getSymbolsAt(SharedSymbol &SS) {
+static SmallSet<SharedSymbol *, 4> getSymbolsAt(SharedSymbol &SS) {
   typedef typename ELFT::Sym Elf_Sym;
 
   SharedFile<ELFT> &File = SS.getFile<ELFT>();
 
-  std::vector<SharedSymbol *> Ret;
+  SmallSet<SharedSymbol *, 4> Ret;
   for (const Elf_Sym &S : File.getGlobalELFSyms()) {
     if (S.st_shndx == SHN_UNDEF || S.st_shndx == SHN_ABS ||
         S.st_value != SS.Value)
       continue;
     StringRef Name = check(S.getName(File.getStringTable()));
     Symbol *Sym = Symtab->find(Name);
-    if (auto *Alias = dyn_cast_or_null<SharedSymbol>(Sym))
-      Ret.push_back(Alias);
+    if (auto *Alias = dyn_cast_or_null<SharedSymbol>(Sym)) {
+      SharedSymbol* SSym = *Ret.insert(Alias).first;
+      SSym->Size = std::max(SSym->Size, Alias->Size);
+    }
   }
   return Ret;
 }


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