[PATCH] D115041: [ELF] Do not report undefined weak references in shared libraries

[Igor Kudrin via Phabricator via llvm-commits]

ikudrin created this revision.
ikudrin added reviewers: MaskRay, psmith, jrtc27.
ikudrin added a project: lld.
Herald added subscribers: arichardson, emaste.
ikudrin requested review of this revision.
Herald added a project: LLVM.

This fixes an issue introduced in D101996 <https://reviews.llvm.org/D101996>.

      

A weak reference in a shared library could be incorrectly reported if there is another library that has a strong reference to the same symbol.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D115041

Files:
  lld/ELF/InputFiles.cpp
  lld/test/ELF/allow-shlib-undefined-weak.s


Index: lld/test/ELF/allow-shlib-undefined-weak.s
===================================================================
--- /dev/null
+++ lld/test/ELF/allow-shlib-undefined-weak.s
@@ -0,0 +1,53 @@
+REQUIRES: x86
+
+RUN: rm -rf %t.dir
+RUN: split-file %s %t.dir
+RUN: cd %t.dir
+
+## Verify that in the following case:
+##
+##   <exec>
+##   +- ref.so (weak reference to foo)
+##   +- wrap.so (non-weak reference to foo)
+##      +- def.so (defines foo)
+##
+## we don't report that foo is undefined in ref.so when linking <exec>.
+
+RUN: llvm-mc -filetype=obj -triple=x86_64 ref.s -o ref.o
+RUN: llvm-mc -filetype=obj -triple=x86_64 wrap.s -o wrap.o
+RUN: llvm-mc -filetype=obj -triple=x86_64 def.s -o def.o
+RUN: ld.lld -shared ref.o -o ref.so
+RUN: ld.lld -shared def.o -o def.so
+RUN: ld.lld -shared wrap.o def.so -o wrap.so
+
+RUN: llvm-mc -filetype=obj -triple=x86_64 start.s -o start.o
+RUN: ld.lld start.o wrap.so ref.so -o /dev/null 2>&1 | \
+RUN:   FileCheck %s --allow-empty
+
+CHECK-NOT: undefined reference to foo [--no-allow-shlib-undefined]
+
+#--- start.s
+.globl _start
+_start:
+  callq wrap_get_foo at PLT
+
+#--- ref.s
+.weak foo
+.globl ref_get_foo
+ref_get_foo:
+  movq foo at GOTPCREL(%rip), %rax
+  movl (%rax), %eax
+  retq
+
+#--- wrap.s
+.globl wrap_get_foo
+wrap_get_foo:
+  movq foo at GOTPCREL(%rip), %rax
+  movl (%rax), %eax
+  retq
+
+#--- def.s
+.data
+.globl foo
+foo:
+  .long 0
Index: lld/ELF/InputFiles.cpp
===================================================================
--- lld/ELF/InputFiles.cpp
+++ lld/ELF/InputFiles.cpp
@@ -1536,7 +1536,7 @@
       Symbol *s = symtab->addSymbol(
           Undefined{this, name, sym.getBinding(), sym.st_other, sym.getType()});
       s->exportDynamic = true;
-      if (s->isUndefined() && !s->isWeak() &&
+      if (s->isUndefined() && sym.getBinding() == STB_GLOBAL &&
           config->unresolvedSymbolsInShlib != UnresolvedPolicy::Ignore)
         requiredSymbols.push_back(s);
       continue;


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