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[ELF] --exclude-libs: don't assign VER_NDX_LOCAL to undefined symbols 

Suggested by Peter Collingbourne.

Non-VER_NDX_GLOBAL versions should not be assigned to defined symbols. --exclude-libs violates this and can cause a spurious error "cannot refer to absolute symbol" after D71795.

excludeLibs incorrectly assigns VER_NDX_LOCAL to an undefined weak symbol =>
isPreemptible is false =>
R_PLT_PC is optimized to R_PC =>
in isStaticLinkTimeConstant, an error is emitted.

Reviewed By: pcc, grimar

Differential Revision: https://reviews.llvm.org/D72681
This commit is contained in:
Fangrui Song 2020-01-13 21:30:05 -08:00
parent 2948ec5ca9
commit 40c5bd4212
2 changed files with 20 additions and 1 deletions
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2
lld/ELF/Driver.cpp
View File

@ -1375,7 +1375,7 @@ static void excludeLibs(opt::InputArgList &args) {
if (!file->archiveName.empty())
if (all || libs.count(path::filename(file->archiveName)))
for (Symbol *sym : file->getSymbols())
if (!sym->isLocal() && sym->file == file)
if (!sym->isUndefined() && !sym->isLocal() && sym->file == file)
sym->versionId = VER_NDX_LOCAL;
};

19
lld/test/ELF/exclude-libs-undef.s Normal file
View File

@ -0,0 +1,19 @@
# REQUIRES: x86
## Test we don't assign VER_NDX_LOCAL to an undefined symbol.
## If we do, an undefined weak will become non-preemptible,
## and we will report an error when an R_PLT_PC (optimized to R_PC)
## references the undefined weak (considered absolute).
# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
# RUN: rm -f %t.a
# RUN: llvm-ar rc %t.a %t.o
# RUN: ld.lld -shared --whole-archive --exclude-libs=ALL %t.a -o %t.so
# RUN: llvm-readelf --dyn-syms %t.so | FileCheck %s
# CHECK: 1: {{.*}} WEAK DEFAULT UND bar
# CHECK-NOT: 2:
.globl foo
.weak bar
foo:
call bar