[ELF] Do not error for missing version when symbol has local version.

If a symbol with an undefined version in a DSO is not going to be
exported into the dynamic symbol table then do not give an error message
for the missing version. This can happen with the --exclude-libs option
which implicitly gives all symbols in a static library the local version.
This matches the behavior of ld.gold and is exploited by the Bionic
dynamic linker on Arm.

Differential Revision: https://reviews.llvm.org/D43126

llvm-svn: 332224

lld/ELF/Symbols.cpp

@@ -196,8 +196,10 @@ void Symbol::parseSymbolVersion() {
   // It is an error if the specified version is not defined.
   // Usually version script is not provided when linking executable,
   // but we may still want to override a versioned symbol from DSO,
-  // so we do not report error in this case.
-  if (Config->Shared)
+  // so we do not report error in this case. We also do not error
+  // if the symbol has a local version as it won't be in the dynamic
+  // symbol table.
+  if (Config->Shared && VersionId != VER_NDX_LOCAL)
     error(toString(File) + ": symbol " + S + " has undefined version " +
           Verstr);
 }

lld/test/ELF/Inputs/versiondef.s

@@ -0,0 +1,9 @@
+.text
+.globl func_impl
+func_impl:
+  ret
+.globl func_impl2
+func_impl2:
+  ret
+.symver func_impl, func@@VER2
+.symver func_impl2, func@VER

lld/test/ELF/version-exclude-libs.s

@@ -0,0 +1,30 @@
+// REQUIRES: x86
+// RUN: llvm-mc %p/Inputs/versiondef.s -o %t.o -filetype=obj -triple=x86_64-pc-linux
+// RUN: llvm-ar -r %t.a %t.o
+// RUN: llvm-mc %s -o %t2.o -filetype=obj -triple=x86_64-pc-linux
+// RUN: ld.lld %t2.o %t.a --shared --exclude-libs ALL -o %t.so
+// RUN: llvm-readobj -symbols %t.so | FileCheck %s
+// RUN: llvm-readobj -dyn-symbols %t.so | FileCheck -check-prefix CHECK-DYN %s
+// RUN: not ld.lld %t2.o %t.a --shared -o %t.so 2>&1 | FileCheck -check-prefix=CHECK-ERR %s
+
+// Test that we do not give an error message for undefined versions when the
+// symbol is not exported to the dynamic symbol table.
+
+// CHECK:          Name: func
+// CHECK-NEXT:     Value:
+// CHECK-NEXT:     Size:
+// CHECK-NEXT:     Binding: Local (0x0)
+
+// CHECK-DYN-NOT: func
+
+// CHECK-ERR: symbol func@@VER2 has undefined version VER2
+// CHECK-ERR-NEXT: symbol func@VER has undefined version VER
+
+ .text
+ .globl _start
+ .globl func
+_start:
+ ret
+
+ .data
+ .quad func