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[MC] [COFF] Make sure that weak external symbols are undefined symbols

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For comdats (e.g. caused by -ffunction-sections), Section is already
set here; make sure it's null, for the weak external symbol to be undefined.

This fixes PR46779.

Differential Revision: https://reviews.llvm.org/D84507
This commit is contained in:
Martin Storsjö 2020-07-21 23:39:37 +03:00
parent e8a94ed276
commit 1d7926a981
2 changed files with 35 additions and 0 deletions
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1
lib/MC/WinCOFFObjectWriter.cpp
View File

@ -375,6 +375,7 @@ void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &MCSym,
COFFSymbol *Local = nullptr;
if (cast<MCSymbolCOFF>(MCSym).isWeakExternal()) {
Sym->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
Sym->Section = nullptr;
COFFSymbol *WeakDefault = getLinkedSymbol(MCSym);
if (!WeakDefault) {

34
test/MC/COFF/weak-comdat.s Normal file
View File

@ -0,0 +1,34 @@
// RUN: llvm-mc -filetype=obj -triple x86_64-pc-win32 %s -o %t.o
// RUN: llvm-readobj --symbols %t.o | FileCheck %s
// Test that the weak symbol is properly undefined, while originally being
// the leader symbol for a comdat. (This can easily happen if building with
// -ffunction-sections).
.section .text$func,"xr",one_only,func
.weak func
func:
ret
// CHECK: Symbol {
// CHECK: Name: func
// CHECK-NEXT: Value: 0
// CHECK-NEXT: Section: IMAGE_SYM_UNDEFINED (0)
// CHECK-NEXT: BaseType: Null (0x0)
// CHECK-NEXT: ComplexType: Null (0x0)
// CHECK-NEXT: StorageClass: WeakExternal (0x69)
// CHECK-NEXT: AuxSymbolCount: 1
// CHECK-NEXT: AuxWeakExternal {
// CHECK-NEXT: Linked: .weak.func.default (10)
// CHECK-NEXT: Search: Alias (0x3)
// CHECK-NEXT: }
// CHECK-NEXT: }
// CHECK-NEXT: Symbol {
// CHECK-NEXT: Name: .weak.func.default
// CHECK-NEXT: Value: 0
// CHECK-NEXT: Section: .text$func (4)
// CHECK-NEXT: BaseType: Null (0x0)
// CHECK-NEXT: ComplexType: Null (0x0)
// CHECK-NEXT: StorageClass: External (0x2)
// CHECK-NEXT: AuxSymbolCount: 0
// CHECK-NEXT: }