[PATCH] D63752: Fix an issue that common symbols are not internalized under some condition.

[Rui Ueyama via Phabricator via llvm-commits]

ruiu created this revision.
ruiu added reviewers: tejohnson, MaskRay.
Herald added subscribers: dexonsmith, steven_wu, arichardson, emaste.
Herald added a reviewer: espindola.
Herald added a project: LLVM.

r360841 introduced CommonSymbol class. An unintended behavioral change
introduced by that change was that common symbols are not internalized
by LTO under some condition, as reported in
https://bugs.llvm.org/show_bug.cgi?id=41978.

This patch fixes that issue.

The issue occurred under the following condition:

1. There exists a common symbol
2. At least one DSO is given to lld

If the above conditions are met, Symbol::includeInDynsym() returned a
wrong value for a common symbol.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D63752

Files:
  lld/ELF/Symbols.cpp
  lld/test/ELF/lto/common4.ll


Index: lld/test/ELF/lto/common4.ll
===================================================================
--- /dev/null
+++ lld/test/ELF/lto/common4.ll
@@ -0,0 +1,13 @@
+; REQUIRES: x86
+; RUN: echo | llvm-mc -filetype=obj -triple=x86_64-unknown-linux -o %t.so.o
+; RUN: ld.lld -shared -o %t.so %t.so.o
+
+; RUN: llvm-as %s -o %t.o
+; RUN: ld.lld %t.o -o %t.exe -save-temps %t.so
+; RUN: llvm-dis < %t.exe.0.2.internalize.bc | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+ at a = common dso_local local_unnamed_addr global i32 0, align 4
+; CHECK-DAG: @a = internal global i32 0, align 4
Index: lld/ELF/Symbols.cpp
===================================================================
--- lld/ELF/Symbols.cpp
+++ lld/ELF/Symbols.cpp
@@ -275,13 +275,13 @@
     return false;
   if (computeBinding() == STB_LOCAL)
     return false;
+
   // If a PIE binary was not linked against any shared libraries, then we can
   // safely drop weak undef symbols from .dynsym.
   if (isUndefWeak() && Config->Pie && SharedFiles.empty())
     return false;
-  if (!isDefined())
-    return true;
-  return ExportDynamic;
+
+  return isUndefined() || isShared() || ExportDynamic;
 }
 
 // Print out a log message for --trace-symbol.


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D63752.206363.patch
Type: text/x-patch
Size: 1287 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20190625/a633c522/attachment.bin>