Open
Description
openedon Oct 9, 2023
See downstream bug:
When building the following code:
void BM_ParentBasedSamplerConstruction(benchmark::State &state)
{
while (state.KeepRunning())
{
benchmark::DoNotOptimize(ParentBasedSampler(std::make_shared<AlwaysOnSampler>())); // line 49
}
}
and
void BM_TraceIdRatioBasedSamplerConstruction(benchmark::State &state)
{
while (state.KeepRunning())
{
benchmark::DoNotOptimize(TraceIdRatioBasedSampler(0.01)); // line 58
}
}
the build fails with GCC 7.4.1, GCC 7.5.0, GCC 12.3.0.
The error reported is:
[ 56%] Building CXX object sdk/test/trace/CMakeFiles/sampler_benchmark.dir/sampler_benchmark.cc.o
In file included from /home/malff/CODE/MARC_GITHUB/opentelemetry-cpp/sdk/test/trace/sampler_benchmark.cc:17:
/opt/benchmark-1.8.2/include/benchmark/benchmark.h: In instantiation of ‘typename std::enable_if<((! std::is_trivially_copyable<_Tp>::value) || (sizeof (Tp) > sizeof (Tp*)))>::type benchmark::DoNotOptimize(Tp&&) [with Tp = opentelemetry::v1::sdk::trace::ParentBasedSampler; typename std::enable_if<((! std::is_trivially_copyable<_Tp>::value) || (sizeof (Tp) > sizeof (Tp*)))>::type = void]’:
/home/malff/CODE/MARC_GITHUB/opentelemetry-cpp/sdk/test/trace/sampler_benchmark.cc:49:29: required from here
/opt/benchmark-1.8.2/include/benchmark/benchmark.h:540:3: error: read-only reference ‘value’ used as ‘asm’ output
540 | asm volatile("" : "+m"(value) : : "memory");
| ^~~
/opt/benchmark-1.8.2/include/benchmark/benchmark.h: In instantiation of ‘typename std::enable_if<((! std::is_trivially_copyable<_Tp>::value) || (sizeof (Tp) > sizeof (Tp*)))>::type benchmark::DoNotOptimize(Tp&&) [with Tp = opentelemetry::v1::sdk::trace::TraceIdRatioBasedSampler; typename std::enable_if<((! std::is_trivially_copyable<_Tp>::value) || (sizeof (Tp) > sizeof (Tp*)))>::type = void]’:
/home/malff/CODE/MARC_GITHUB/opentelemetry-cpp/sdk/test/trace/sampler_benchmark.cc:58:29: required from here
/opt/benchmark-1.8.2/include/benchmark/benchmark.h:540:3: error: read-only reference ‘value’ used as ‘asm’ output
make[2]: *** [sdk/test/trace/CMakeFiles/sampler_benchmark.dir/build.make:76: sdk/test/trace/CMakeFiles/sampler_benchmark.dir/sampler_benchmark.cc.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:4217: sdk/test/trace/CMakeFiles/sampler_benchmark.dir/all] Error 2
make: *** [Makefile:146: all] Error 2
Verified with benchmark 1.8.2 and 1.8.3.
Note that the same code builds fine with CLang.
If this matters, ParentBasedSampler and TraceIdRatioBasedSampler are classes: what is benchmarked here is a call to the constructor.
Note how the benchmark header file is different for GCC, with:
The build failure occurs in:
template <class Tp>
inline BENCHMARK_ALWAYS_INLINE
typename std::enable_if<!std::is_trivially_copyable<Tp>::value ||
(sizeof(Tp) > sizeof(Tp*))>::type
DoNotOptimize(Tp&& value) {
asm volatile("" : "+m"(value) : : "memory"); // line 540
}
Expected result is a successful build with both GCC and Clang.
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