[llvm-dev] Issue combining SanitizerCoverage with LTO

[Roman Lebedev via llvm-dev]

I believe i have reported a related issue in
https://bugs.llvm.org/show_bug.cgi?id=41734
"-fsanitize-coverage=inline-8bit-counters + ThinLTO = lld crash"

On Wed, Dec 4, 2019 at 12:56 AM Eli Friedman via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
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> An issue was reported to me that involved using “-fsanitize-coverage=trace-pc-guard -flto=thin”.
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> Currently, what seems to happen is that the sancov instrumentation gets inserted at compile-time, then at LTO-time some instrumented functions get erased.  The associated sancov globals don’t get erased, though.  The end result is that some sancov globals have null MD_associated metadata, and the linker prints an error like “incompatible section flags for __sancov_guards”.  This seems to happen for any program where a function is erased at link time.  For example, the following program:
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> void testfn(){}
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> __attribute((visibility("hidden"))) void testfn2(){}
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> I’m not sure how __sancov_guards is supposed to work in this context.  Is LTO misbehaving, or is SanitizerCoverage making bad assumptions?
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> -Eli
Roman

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