[PATCH] D35059: [ELF] - Handle symbols with default version early.

[George Rimar via Phabricator via llvm-commits]

grimar created this revision.
Herald added a subscriber: emaste.

This fixes last testcase provided in PR28414.
In short issue is next: when we had X@@Version symbol in object A,
we did not resolve it to X early. Then when in another object B
we had reference to undefined X, symbol X from archive was fetched.
Since both archive and object A contains another symbol Z, duplicate
symbol definition was triggered as a result.

Correct behavior is to use X@@Version from object A instead and do not fetch
any symbols from archive.


https://reviews.llvm.org/D35059

Files:
  ELF/SymbolTable.cpp
  test/ELF/Inputs/symver-archive1.s
  test/ELF/Inputs/symver-archive2.s
  test/ELF/symver-archive.s


Index: test/ELF/symver-archive.s
===================================================================
--- test/ELF/symver-archive.s
+++ test/ELF/symver-archive.s
@@ -0,0 +1,15 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t1
+# RUN: rm -f %t.a
+# RUN: llvm-ar rcs %t.a %t1
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %S/Inputs/symver-archive1.s -o %t2.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %S/Inputs/symver-archive2.s -o %t3.o
+# RUN: ld.lld -o %t.out %t2.o %t3.o %t.a
+
+.text
+.globl x
+.type x, @function
+x:
+
+.globl xx
+xx = x
Index: test/ELF/Inputs/symver-archive2.s
===================================================================
--- test/ELF/Inputs/symver-archive2.s
+++ test/ELF/Inputs/symver-archive2.s
@@ -0,0 +1 @@
+call xx at PLT
Index: test/ELF/Inputs/symver-archive1.s
===================================================================
--- test/ELF/Inputs/symver-archive1.s
+++ test/ELF/Inputs/symver-archive1.s
@@ -0,0 +1,6 @@
+.text
+.globl x
+.type x, @function
+x:
+
+.symver x, xx@@VER
Index: ELF/SymbolTable.cpp
===================================================================
--- ELF/SymbolTable.cpp
+++ ELF/SymbolTable.cpp
@@ -211,6 +211,13 @@
 // Find an existing symbol or create and insert a new one.
 template <class ELFT>
 std::pair<Symbol *, bool> SymbolTable<ELFT>::insert(StringRef Name) {
+  // <name>@@<version> means the symbol is the default version. In that
+  // case symbol <name> must exist and <name>@@<version> will be used to
+  // resolve references to <name>.
+  size_t Pos = Name.find("@@");
+  if (Pos != StringRef::npos)
+    Name = Name.take_front(Pos);
+
   auto P = Symtab.insert(
       {CachedHashStringRef(Name), SymIndex((int)SymVector.size(), false)});
   SymIndex &V = P.first->second;
@@ -712,31 +719,14 @@
       B->symbol()->VersionId = VersionId;
 }
 
-static bool isDefaultVersion(SymbolBody *B) {
-  return B->isInCurrentDSO() && B->getName().find("@@") != StringRef::npos;
-}
-
 // This function processes version scripts by updating VersionId
 // member of symbols.
 template <class ELFT> void SymbolTable<ELFT>::scanVersionScript() {
   // Symbol themselves might know their versions because symbols
   // can contain versions in the form of <name>@<version>.
   // Let them parse and update their names to exclude version suffix.
-  for (Symbol *Sym : SymVector) {
-    SymbolBody *Body = Sym->body();
-    bool IsDefault = isDefaultVersion(Body);
-    Body->parseSymbolVersion();
-
-    if (!IsDefault)
-      continue;
-
-    // <name>@@<version> means the symbol is the default version. If that's the
-    // case, the symbol is not used only to resolve <name> of version <version>
-    // but also undefined unversioned symbols with name <name>.
-    SymbolBody *S = find(Body->getName());
-    if (S && S->isUndefined())
-      S->copy(Body);
-  }
+  for (Symbol *Sym : SymVector)
+    Sym->body()->parseSymbolVersion();
 
   // Handle edge cases first.
   handleAnonymousVersion();


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