diff --git a/lld/MachO/InputFiles.cpp b/lld/MachO/InputFiles.cpp --- a/lld/MachO/InputFiles.cpp +++ b/lld/MachO/InputFiles.cpp @@ -282,16 +282,24 @@ } else { auto *isec = make(segname, name, this, data, align, flags); - if (!(isDebugSection(isec->getFlags()) && - isec->getSegName() == segment_names::dwarf)) { - subsections.push_back({{0, isec}}); - } else { + if (isDebugSection(isec->getFlags()) && + isec->getSegName() == segment_names::dwarf) { // Instead of emitting DWARF sections, we emit STABS symbols to the // object files that contain them. We filter them out early to avoid // parsing their relocations unnecessarily. But we must still push an // empty map to ensure the indices line up for the remaining sections. subsections.push_back({}); debugSections.push_back(isec); + } else if (isec->getSegName() == segment_names::llvm) { + // ld64 does not appear to emit contents from sections within the __LLVM + // segment. Symbols within those sections point to bitcode metadata + // instead of actual symbols. Global symbols within those sections could + // have the same name without causing duplicate symbol errors. Push an + // empty map to ensure indices line up for the remaining sections. + // TODO: Evaluate whether the bitcode metadata is needed. + subsections.push_back({}); + } else { + subsections.push_back({{0, isec}}); } } } diff --git a/lld/test/MachO/discard-llvm-sections.s b/lld/test/MachO/discard-llvm-sections.s new file mode 100644 --- /dev/null +++ b/lld/test/MachO/discard-llvm-sections.s @@ -0,0 +1,46 @@ +# REQUIRES: x86 +# RUN: rm -rf %t; split-file %s %t +# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/foo.s -o %t/foo.o +# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/bar.s -o %t/bar.o + +## "_llvm." symbols are not special. LLD would produce duplicate symbol errors +## if they were not within the LLVM segment. + +## 1/ Test that LLD does not produce duplicate symbols errors when linking global symbols +## with the same name under the LLVM segment. +# RUN: %lld -dylib %t/foo.o %t/bar.o -o %t/libDuplicate.dylib + +## 2/ Test that all sections within an LLVM segment are dropped. +# RUN: llvm-objdump --section-headers %t/libDuplicate.dylib | FileCheck %s + +# CHECK-LABEL: Sections: +# CHECK-NEXT: Idx Name Size VMA Type +# CHECK-NEXT: 0 __text 00000000 {{[0-9a-f]+}} TEXT + +## 3/ Test that linking global symbol that is not under the LLVM segment produces duplicate +## symbols +# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin --defsym TEXT=0 %t/foo.s -o %t/foo.o +# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin --defsym TEXT=0 %t/bar.s -o %t/bar.o +# RUN: not %lld -dylib %t/foo.o %t/bar.o -o %t/libDuplicate.dylib 2>&1 | FileCheck %s --check-prefix=DUP + +# DUP: ld64.lld: error: duplicate symbol: _llvm.foo + +#--- foo.s +.globl _llvm.foo +.ifdef TEXT + .section __TEXT,__cstring +.else + .section __LLVM,__bitcode +.endif + _llvm.foo: + .asciz "test" + +#--- bar.s +.globl _llvm.foo +.ifdef TEXT + .section __TEXT,__cstring +.else + .section __LLVM,__bitcode +.endif + _llvm.foo: + .asciz "test"