[BUG] BENCHMARK macros do not reference full namespace for make_unique

[pitrou]

Describe the bug
In #1948 the various BENCHMARK macros were changed to something like:

#define BENCHMARK(...)                                                \
  BENCHMARK_PRIVATE_DECLARE(_benchmark_) =                            \
      (::benchmark::internal::RegisterBenchmarkInternal(              \
          benchmark::internal::make_unique<                           \
              ::benchmark::internal::FunctionBenchmark>(#__VA_ARGS__, \
                                                        __VA_ARGS__)))

This makes a relatively namespace lookup for benchmark::internal::make_unique even though the macros can be invoked from any namespace.

If the user code defined their own benchmark namespace, then the compiler fails finding make_unique. This produces errors in the Apache Arrow continuous benchmarking, for example here.

[dmah42]

oh this is only in the case that

#if (__cplusplus < 201402L || (defined(_MSC_VER) && _MSVC_LANG < 201402L))

right?

[pitrou]

I don't think, this is Linux builds with C++17.

[pitrou]

Here is a build log (g++ with -std=c++17):
https://buildkite.com/apache-arrow/arrow-bci-benchmark-on-amd64-c6a-4xlarge-linux/builds/937#0195d209-e346-4c84-8895-b82b61d1a899/95-2687

[dmah42]

then that macro should be reducing to ::std::make_unique as it does for the CI bots.

what version of g++?

[pitrou]

Please read again. The problem is that benchmark::internal::make_unique fails looking up as it does not look in the top-level ::benchmark namespace. benchmark is relative and will be looked up in the context where the macro is being used.

In other words, if I have a namespace parquet::benchmark where these macros are used, benchmark::internal::make_unique will be interpreted as parquet::benchmark::internal::make_unique.

[pitrou]

You're correctly using ::benchmark::internal::... in most places in these macros, but for make_unique you're using benchmark::internal::... which is where the issue comes from.

[dmah42]

got it.

[georgthegreat]

@LebedevRI, could you, please tag a new release including this fixup?

[LebedevRI]

@dmah42

[dmah42]

https://github.com/google/benchmark/releases/tag/v1.9.3