[CMake] Checking for compatible compiler flags

[Michael Hertling]

On 08/07/2011 09:33 PM, Hans Johnson wrote:
> Hello,
> 
> I'm trying to use the cmake feature for testing if compiler flags are valid,
> but I am running into trouble with these two complier flags.  I can not
> figure out how to proper escape the "+" or the "%" that I believe are
> causing the failures.
> 
> cat CMakeLists.txt 
> ============================================
> project(TestCompilerFlagTest)
> 
> include(CheckCCompilerFlag)
> include(CheckCXXCompilerFlag)
> 
> set(flag -Wno-c++0x-static-nonintegral-init)
> check_cxx_compiler_flag(${flag} CXX_HAS_WARNING${flag})
> set(flag -features=no%anachronisms )
> check_cxx_compiler_flag(${flag} CXX_HAS_WARNING${flag})
> ============================================
> 
> I'd appreciate any help in resolving this.
> 
> A more robust version of  /opt/cmake-2.8.4-Darwin-universal/CMake
> 2.8-4.app/Contents/share/cmake-2.8/Modules/CheckCXXCompilerFlag.cmake
>  for use in ITK (and Slicer/SimpleITK/BRAINS) would also be acceptable.
> 
> Thanks in advance.
> 
> Hans

The result variable's name, i.e. CHECK_CXX_COMPILER_FLAG()'s second
argument, undergoes a regex evaluation in CHECK_CXX_SOURCE_COMPILES(),
so it mustn't contain regex-sensitive characters like "+". The "=" and
"%" in the other test seem to pass CHECK_CXX_COMPILER_FLAG(), but bail
out on another occasion. In general, IMO, using any special characters
except for "_" in identifiers means asking for trouble. Thus, restrict
yourself to "[A-Za-z][A-Za-z0-9_]*" - or "[A-Za-z_][A-Za-z0-9_]*" with
regard to internal variables - and your issue will probably go away.

Regards,

Michael