[cfe-dev] Questions on reproducibility/deterministic build

[David Blaikie via cfe-dev]

Could you provide a small standalone example and precise commands to
reproduce the case you're describing?

On Wed, Jan 13, 2021 at 9:06 AM Oleksiy Obitotskyi -X (oobitots -
GLOBALLOGIC INC at Cisco) via cfe-dev <cfe-dev at lists.llvm.org> wrote:

> Hi,
>
>
> I'm working on reproducibility (or deterministic build) issues with clang.
>
> And I got issue with compiler-rt libraries, some of the debug symbols
> comes with source absolute path, e.g.:
>
>
> strings ./build/lib64/linux/libclang_rt.fuzzer-x86_64.a | grep "lambda at"
>
> ...
>
> ---8<--- A
>
> CollectFeatures<(lambda at
> /compiler-rt/lib/fuzzer/FuzzerDriver.cpp:482:25)>
>
> ...
>
> ---8<--- B
>
> void fuzzer::TracePC::IterateInline8bitCounters(CallBack) [CallBack =
> (lambda at
>
> <some-path>/compiler-rt/lib/fuzzer/FuzzerTracePC.cpp:77:29)]
> void fuzzer::TracePC::IterateInline8bitCounters(CallBack) [CallBack =
> (lambda at
>
> <some-path>/compiler-rt/lib/fuzzer/FuzzerTracePC.cpp:85:29)]
> void fuzzer::TracePC::IterateInline8bitCounters(CallBack) [CallBack =
> (lambda at
>
> <some-path>/compiler-rt/lib/fuzzer/FuzzerTracePC.cpp:99:29)]
> void fuzzer::TracePC::IterateInline8bitCounters(CallBack) [CallBack =
> (lambda at
>
> <some-path>/compiler-rt/lib/fuzzer/FuzzerTracePC.cpp:206:33)]
> void fuzzer::TracePC::IterateCoveredFunctions(CallBack) [CallBack =
> (lambda at
>
> <some-path>/compiler-rt/lib/fuzzer/FuzzerTracePC.cpp:314:34)]
>
> ---8<--- C
> IterateInline8bitCounters<(lambda at
> /compiler-rt/lib/fuzzer/FuzzerTracePC.cpp:77:29)>
> IterateInline8bitCounters<(lambda at
> /compiler-rt/lib/fuzzer/FuzzerTracePC.cpp:85:29)>
> IterateInline8bitCounters<(lambda at
> /compiler-rt/lib/fuzzer/FuzzerTracePC.cpp:99:29)>
> IterateInline8bitCounters<(lambda at
> /compiler-rt/lib/fuzzer/FuzzerTracePC.cpp:206:33)>
> IterateCoveredFunctions<(lambda at
> /compiler-rt/lib/fuzzer/FuzzerTracePC.cpp:314:34)>
>
> ...
>
>
> Conditions:
>
> - clang version 7 used.
>
> - flags -ffile-prefix-map/debug-prefix-map/macro-prefix-map <some-path>
> are set during compilation
>
> - patch backported
> https://github.com/llvm/llvm-project/commit/56acd5a66ea3800a23be0cfdbc422624398cb096
>
>
> In section A and C debug symbols for lambda have path correctly remapped
> with prefix set in -f<file/debug/macro>-prefix-map.
>
> But section B debug symbols for the same lambda code goes without
> remapping (and it's ok TypePrinter code works properly in this case).
>
>
> For section B TypePrinter::printTag called with
> PrintingPolicy.RemapFilePaths set, but for section A the same function
> called with different PrintingPolicy and RemapFilePaths is not set.
>
>
>
> - I'm not sure is it ok that two sections generated in different way and
> what is the reason for this? The similar code with lambdas from section A
> produce only one symbol type with remapped path.
>
>
> - Is it possible and is it make sense to pass CGDebugInfo settings to the
> code Sema::BuildPredefinedExpr to apply
>
> RemapFilePaths settings to the PrintingPolicy used? As I
> understand symbols could be generated into different compilation
> stages/passes and some code generation settings could not be applied
> directly during other stages.
>
>
> Regards,
>
> Oleksiy
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>
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