编译器标志在CMake CHECK

编译器标志在CMake CHECK_CXX_COMPILER_FLAG中检查两次(Compiler flag checked twice in CMake CHECK_CXX_COMPILER_FLAG)

我使用自定义宏来检查并在CMAKE中为编译添加编译器标志。我用于此的代码是：

MACRO(CheckAndAddFlag flag) # We cannot check for -Wno-foo as this won't throw a warning so we must check for the -Wfoo option directly # http://stackoverflow.com/questions/38785168/cc1plus-unrecognized-command-line-option-warning-on-any-other-warning STRING(REGEX REPLACE "^-Wno-" "-W" checkedFlag ${flag}) SET(VarName ${checkedFlag}) STRING(REPLACE "+" "X" VarName ${VarName}) STRING(REPLACE "-" "_" VarName ${VarName}) # Avoid double checks. A compiler will not magically support a flag it did not before MESSAGE(STATUS "Checking CXX_FLAG_${VarName}_SUPPORTED. Checked? ${VarName}_CHECKED= ${${VarName}_CHECKED} end") if(NOT ${VarName}_CHECKED) CHECK_CXX_COMPILER_FLAG(${checkedFlag} CXX_FLAG_${VarName}_SUPPORTED) CHECK_C_COMPILER_FLAG(${checkedFlag} C_FLAG_${VarName}_SUPPORTED) set(${VarName}_CHECKED YES CACHE INTERNAL "") MESSAGE(STATUS "Checked CXX_FLAG_${VarName}_SUPPORTED. Checked? ${VarName}_CHECKED= ${${VarName}_CHECKED} end") endif() IF (CXX_FLAG_${VarName}_SUPPORTED) set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${flag}") ENDIF () IF (C_FLAG_${VarName}_SUPPORTED) set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${flag}") ENDIF () unset(VarName) unset(checkedFlag) ENDMACRO()

我称之为：

CheckAndAddFlag("-Wno-error=type-limits") CheckAndAddFlag("-Wfloat-conversion")

通常它应该只检查每个标志一次，设置它的变量，然后运行CMake应该找到它并且不再检查它（try_compile与MSVC非常缓慢）它适用于大多数标志，但它不适用于-Wno-error=type-limits 。这里根据输出对标志进行双重检查。因此我添加了_CHECKED变量来解决这个问题，但即使这样也行不通。它会被再次检查。

一些输出：

Checking CXX_FLAG__Werror=type_limits_SUPPORTED. Checked? _Werror=type_limits_CHECKED= end Performing Test CXX_FLAG__Werror=type_limits_SUPPORTED Performing Test CXX_FLAG__Werror=type_limits_SUPPORTED - Failed Performing Test C_FLAG__Werror=type_limits_SUPPORTED Performing Test C_FLAG__Werror=type_limits_SUPPORTED - Failed Checked CXX_FLAG__Werror=type_limits_SUPPORTED. Checked? _Werror=type_limits_CHECKED= YES end Checking CXX_FLAG__Wfloat_conversion_SUPPORTED. Checked? _Wfloat_conversion_CHECKED= YES end Checking CXX_FLAG__Wlong_long_SUPPORTED. Checked? _Wlong_long_CHECKED= YES end

任何想法为什么会这样？为什么变量设置但在下一次CMAKE运行中未设置，为什么只有这个？

I use a custom macro to check and add a compiler flag to the compilation in CMAKE. The code I use for this is that:

MACRO(CheckAndAddFlag flag) # We cannot check for -Wno-foo as this won't throw a warning so we must check for the -Wfoo option directly # http://stackoverflow.com/questions/38785168/cc1plus-unrecognized-command-line-option-warning-on-any-other-warning STRING(REGEX REPLACE "^-Wno-" "-W" checkedFlag ${flag}) SET(VarName ${checkedFlag}) STRING(REPLACE "+" "X" VarName ${VarName}) STRING(REPLACE "-" "_" VarName ${VarName}) # Avoid double checks. A compiler will not magically support a flag it did not before MESSAGE(STATUS "Checking CXX_FLAG_${VarName}_SUPPORTED. Checked? ${VarName}_CHECKED= ${${VarName}_CHECKED} end") if(NOT ${VarName}_CHECKED) CHECK_CXX_COMPILER_FLAG(${checkedFlag} CXX_FLAG_${VarName}_SUPPORTED) CHECK_C_COMPILER_FLAG(${checkedFlag} C_FLAG_${VarName}_SUPPORTED) set(${VarName}_CHECKED YES CACHE INTERNAL "") MESSAGE(STATUS "Checked CXX_FLAG_${VarName}_SUPPORTED. Checked? ${VarName}_CHECKED= ${${VarName}_CHECKED} end") endif() IF (CXX_FLAG_${VarName}_SUPPORTED) set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${flag}") ENDIF () IF (C_FLAG_${VarName}_SUPPORTED) set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${flag}") ENDIF () unset(VarName) unset(checkedFlag) ENDMACRO()

And I call it e.g. with:

CheckAndAddFlag("-Wno-error=type-limits") CheckAndAddFlag("-Wfloat-conversion")

Normally it should only check each flag once, set its variable and following runs of CMake should find this and don't check it again (try_compile with MSVC is painfully slow) It does work for most of the flags, but it does not work with -Wno-error=type-limits. Here the flag gets double checked according to the output. Hence I added the _CHECKED variable to work around this, but even this does not work. It sill gets checked again.

Some output:

Checking CXX_FLAG__Werror=type_limits_SUPPORTED. Checked? _Werror=type_limits_CHECKED= end Performing Test CXX_FLAG__Werror=type_limits_SUPPORTED Performing Test CXX_FLAG__Werror=type_limits_SUPPORTED - Failed Performing Test C_FLAG__Werror=type_limits_SUPPORTED Performing Test C_FLAG__Werror=type_limits_SUPPORTED - Failed Checked CXX_FLAG__Werror=type_limits_SUPPORTED. Checked? _Werror=type_limits_CHECKED= YES end Checking CXX_FLAG__Wfloat_conversion_SUPPORTED. Checked? _Wfloat_conversion_CHECKED= YES end Checking CXX_FLAG__Wlong_long_SUPPORTED. Checked? _Wlong_long_CHECKED= YES end

Any ideas why this is happening? Why does the variable get set but is unset in the next CMAKE run and why only this?