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[ELF] --fortran-common: prefer STB_WEAK to COMMON 

The ELF specification says "The link editor honors the common definition and
ignores the weak ones." GNU ld and our Symbol::compare follow this, but the
--fortran-common code (D86142) made a mistake on the precedence.

Fixes https://bugs.llvm.org/show_bug.cgi?id=51082

Reviewed By: peter.smith, sfertile

Differential Revision: https://reviews.llvm.org/D105945
This commit is contained in:
Fangrui Song 2021-07-14 10:18:30 -07:00
parent 338314f9c2
commit 7de2173c2a
2 changed files with 21 additions and 5 deletions
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7
lld/ELF/InputFiles.cpp
View File

@ -1262,7 +1262,7 @@ void ArchiveFile::fetch(const Archive::Symbol &sym) {
//
// 2) Consider the tentative definition as still undefined (ie the promotion to
// a real definition happens only after all symbol resolution is done).
// The linker searches archive members for global or weak definitions to
// The linker searches archive members for STB_GLOBAL definitions to
// replace the tentative definition with. This is the behavior used by
// GNU ld.
//
@ -1278,7 +1278,7 @@ static bool isBitcodeNonCommonDef(MemoryBufferRef mb, StringRef symName,
for (const irsymtab::Reader::SymbolRef &sym :
symtabFile.TheReader.symbols()) {
if (sym.isGlobal() && sym.getName() == symName)
return !sym.isUndefined() && !sym.isCommon();
return !sym.isUndefined() && !sym.isWeak() && !sym.isCommon();
}
return false;
}
@ -1292,7 +1292,8 @@ static bool isNonCommonDef(MemoryBufferRef mb, StringRef symName,
for (auto sym : obj->template getGlobalELFSyms<ELFT>()) {
Expected<StringRef> name = sym.getName(stringtable);
if (name && name.get() == symName)
return sym.isDefined() && !sym.isCommon();
return sym.isDefined() && sym.getBinding() == STB_GLOBAL &&
!sym.isCommon();
}
return false;
}

19
lld/test/ELF/common-archive-lookup.s
View File

@ -20,6 +20,7 @@
## Bitcode files.
# RUN: llvm-as -o 1.bc commonblock.ll
# RUN: llvm-as -o 2.bc blockdata.ll
# RUN: llvm-as -o 3.bc weak.ll
## Bitcode archive.
# RUN: llvm-ar crs 4.a 1.bc 2.bc
@ -31,10 +32,10 @@
# RUN: llvm-objdump -D -j .data 2 | FileCheck --check-prefix=TEST1 %s
# RUN: ld.lld -o 3 main.o 2.a
# RUN: llvm-objdump -D -j .data 3 | FileCheck --check-prefix=TEST1 %s
# RUN: llvm-objdump -t 3 | FileCheck --check-prefix=BSS %s
# RUN: ld.lld -o 4 main.o --start-lib 1.o weak_data_only.o --end-lib
# RUN: llvm-objdump -D -j .data 4 | FileCheck --check-prefix=TEST1 %s
# RUN: llvm-objdump -t 4 | FileCheck --check-prefix=BSS %s
# RUN: ld.lld -o 5 main.o 3.a --print-map | FileCheck --check-prefix=MAP %s
@ -63,6 +64,9 @@
# RUN: ld.lld -o - main.o --start-lib 1.bc 2.bc --end-lib --lto-emit-asm | \
# RUN: FileCheck --check-prefix=ASM %s
## COMMON overrides weak. Don't extract 3.bc which provides a weak definition.
# RUN: ld.lld -o /dev/null main.o --start-lib 1.bc 3.bc --end-lib -y block | FileCheck --check-prefix=LTO_WEAK %s
## Old FORTRAN that mixes use of COMMON blocks and BLOCK DATA requires that we
## search through archives for non-tentative definitions (from the BLOCK DATA)
## to replace the tentative definitions (from the COMMON block(s)).
@ -75,6 +79,7 @@
# TEST1-NEXT: fb 21 09 40
# TEST1-NEXT: ...
# BSS: [[#%x,]] g O .bss 0000000000000028 block
# NFC: Name: block
# NFC-NEXT: Value:
@ -100,6 +105,10 @@
# ASM-NEXT: .long 5
# ASM: .size block, 20
# LTO_WEAK: 1.bc: common definition of block
# LTO_WEAK: <internal>: reference to block
# LTO_WEAK-NOT: {{.}}
#--- ref.s
.text
.abiversion 2
@ -167,6 +176,12 @@ target triple = "powerpc64le-unknown-linux-gnu"
@block = dso_local local_unnamed_addr global [5 x i32] [i32 5, i32 0, i32 0, i32 0, i32 0], align 4
#--- weak.ll
target datalayout = "e-m:e-i64:64-n32:64-S128-v256:256:256-v512:512:512"
target triple = "powerpc64le-unknown-linux-gnu"
@block = weak dso_local global [5 x i32] [i32 5, i32 0, i32 0, i32 0, i32 0], align 4
#--- commonblock.ll
target datalayout = "e-m:e-i64:64-n32:64-S128-v256:256:256-v512:512:512"
target triple = "powerpc64le-unknown-linux-gnu"