[PATCH] D136078: Use-after-return sanitizer binary metadata

[Marco Elver via Phabricator via cfe-commits]

melver added a comment.

In D136078#3964100 <https://reviews.llvm.org/D136078#3964100>, @dvyukov wrote:

> @melver Re this failure:
>
>   ******************** TEST 'Clang :: Instrumentation/SanitizerBinaryMetadata/uar.cpp' FAILED ********************
>   Script:
>   --
>   : 'RUN: at line 4';   /home/buildbot/as-worker-91/clang-with-lto-ubuntu/build/stage1/bin/clang --driver-mode=g++ /home/buildbot/as-worker-91/clang-with-lto-ubuntu/llvm-project/clang/test/Instrumentation/SanitizerBinaryMetadata/uar.cpp -o /home/buildbot/as-worker-91/clang-with-lto-ubuntu/build/stage1/tools/clang/test/Instrumentation/SanitizerBinaryMetadata/Output/uar.cpp.tmp -fexperimental-sanitize-metadata=covered,uar && /home/buildbot/as-worker-91/clang-with-lto-ubuntu/build/stage1/tools/clang/test/Instrumentation/SanitizerBinaryMetadata/Output/uar.cpp.tmp | /home/buildbot/as-worker-91/clang-with-lto-ubuntu/build/stage1/bin/FileCheck /home/buildbot/as-worker-91/clang-with-lto-ubuntu/llvm-project/clang/test/Instrumentation/SanitizerBinaryMetadata/uar.cpp
>   --
>   Exit Code: 1
>   Command Output (stderr):
>   --
>   /usr/local/bin/ld: sanmd_covered has both ordered [`sanmd_covered[_Z7consumeIjET_RPKcS2_]' in /tmp/lit-tmp-2jisr97l/uar-d5d8d4.o] and unordered [`sanmd_covered[__dummy_sanmd_covered]' in /tmp/lit-tmp-2jisr97l/uar-d5d8d4.o] sections
>   /usr/local/bin/ld: final link failed: Bad value
>   clang-16: error: linker command failed with exit code 1 (use -v to see invocation)
>
> https://lab.llvm.org/buildbot/#/builders/124/builds/5759/steps/7/logs/stdio
>
> This looks like a latent issue which is just exposed by the test.
>
> As far as I understand this happens because this dummy variable somehow ends up in an "unordered" section, while other "real" metadata objects end up in "ordered" sections:
>
>   void SanitizerBinaryMetadata::createZeroSizedObjectInSection(
>       Type *Ty, StringRef SectionSuffix) {
>     auto *DummyInit = ConstantAggregateZero::get(ArrayType::get(Ty, 0));
>     auto *DummyEntry = new GlobalVariable(Mod, DummyInit->getType(), true,
>                                           GlobalVariable::ExternalLinkage,
>                                           DummyInit, "__dummy_" + SectionSuffix);
>     DummyEntry->setSection(getSectionName(SectionSuffix));
>     DummyEntry->setVisibility(GlobalValue::HiddenVisibility);
>     if (TargetTriple.supportsCOMDAT())
>       DummyEntry->setComdat(Mod.getOrInsertComdat(DummyEntry->getName()));
>     // Make sure the section isn't discarded by gc-sections.
>     appendToUsed(Mod, DummyEntry);
>   }
>
> I don't see any method on GlobalVariable to set the section to "ordered".
>
> The only idea I have is to print dummy object in AsmPrinter the same way we print all other metadata objects (then I assume it will have the same properties as other objects).
>
> Do you have any other ideas on how to dead with this?

It's strange we've not encountered this elsewhere - this must be some special (old?) linker. I'll investigate...


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