Fix Clang builds on Windows (#1021)

Fixes #974. The `cxx_feature_check` now has an additional
optional argument which can be used to supply extra cmake flags
to pass to the `try_compile` command. The `CMAKE_CXX_STANDARD=14`
flag was determined to be the minimum flag necessary to correctly
compile and run the regex feature checks when compiling with Clang
under Windows (n.b. this does *not* refer to clang-cl, the frontend
to the MSVC compiler). The additional flag is not enabled for any
other compiler/platform tuple.
This commit is contained in:
Jeremy Ong 2020-08-27 04:17:19 -06:00 committed by GitHub
parent 4857962394
commit 01c0ab7cbb
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 15 additions and 3 deletions

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@ -245,11 +245,17 @@ if (BENCHMARK_USE_LIBCXX)
endif()
endif(BENCHMARK_USE_LIBCXX)
set(EXTRA_CXX_FLAGS "")
if (WIN32 AND "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
# Clang on Windows fails to compile the regex feature check under C++11
set(EXTRA_CXX_FLAGS "-DCMAKE_CXX_STANDARD=14")
endif()
# C++ feature checks
# Determine the correct regular expression engine to use
cxx_feature_check(STD_REGEX)
cxx_feature_check(GNU_POSIX_REGEX)
cxx_feature_check(POSIX_REGEX)
cxx_feature_check(STD_REGEX ${EXTRA_CXX_FLAGS})
cxx_feature_check(GNU_POSIX_REGEX ${EXTRA_CXX_FLAGS})
cxx_feature_check(POSIX_REGEX ${EXTRA_CXX_FLAGS})
if(NOT HAVE_STD_REGEX AND NOT HAVE_GNU_POSIX_REGEX AND NOT HAVE_POSIX_REGEX)
message(FATAL_ERROR "Failed to determine the source files for the regular expression backend")
endif()
@ -257,6 +263,7 @@ if (NOT BENCHMARK_ENABLE_EXCEPTIONS AND HAVE_STD_REGEX
AND NOT HAVE_GNU_POSIX_REGEX AND NOT HAVE_POSIX_REGEX)
message(WARNING "Using std::regex with exceptions disabled is not fully supported")
endif()
cxx_feature_check(STEADY_CLOCK)
# Ensure we have pthreads
set(THREADS_PREFER_PTHREAD_FLAG ON)

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@ -27,6 +27,11 @@ function(cxx_feature_check FILE)
return()
endif()
if (ARGC GREATER 1)
message(STATUS "Enabling additional flags: ${ARGV1}")
list(APPEND BENCHMARK_CXX_LINKER_FLAGS ${ARGV1})
endif()
if (NOT DEFINED COMPILE_${FEATURE})
message(STATUS "Performing Test ${FEATURE}")
if(CMAKE_CROSSCOMPILING)