[CMake] Visual Studio Warning Level

[Judicaël Bedouet]

Hello,

I'm very interested in the fact that CMake could offer possibilities
to portably set default warning levels.

All people, with who I work, wondered a day how to set warning flags,
especially for gcc (Flag /W3 is already set for Visual Studio).

Different simple solutions have been found but they are not satisfactory:
- change CMAKE_C_FLAGS CMAKE_CXX_FLAGS variables when generating
files, but you could forget to do it
- set warnings in the root CMakeLists ( set (CMAKE_CXX_FLAGS
"${CMAKE_CXX_FLAGS} -Wall") ), but you can't dynamically change
warning levels


I have written some macros to portably and easily set default warning
levels but it only works for gcc/g++ and Visual Studio (See
attachment)
Macros WARNINGS, FULL_WARNINGS, NO_WARNINGS and WARNINGS_AS_ERRORS are
used to set default warning levels.
I need a REMOVE_FLAGS macro to remove flag /W3 from Visual Studio
flags (and some others if needed).
Macros WARNING_AS_ERROR and SUPPRESS_WARNING are used to set specific
flags for a platform.
It's pretty poor but it's sufficient for our projects.


I love the idea to set warning flags in platform files but I don't
understand why new files must be created. Is not it possible to add
warning variables to existent platform files in Modules/Platform ?

I wonder if it would be possible to add a CMAKE_WARNING_LEVEL variable
(like CMAKE_BUILD_TYPE) which could take values like Warning1,
Warning2, Warning3, Warning4 (or All, Full, No).
So we could define in platform files CMAKE_CXX_FLAGS_WARNING1_INIT,
CMAKE_CXX_FLAGS_WARNING2_INIT... variables (like
CMAKE_CXX_FLAGS_DEBUG_INIT, CMAKE_CXX_FLAGS_RELEASE_INIT).
The final default value for CMAKE_CXX_FLAGS would be
"${CMAKE_CXX_FLAGS_INIT} ${CMAKE_CXX_FLAGS_${CMAKE_BUILD_TYPE}_INIT}
${CMAKE_CXX_FLAGS_${CMAKE_WARNING_LEVEL}_INIT}".

I think it would be a great idea that CMake provide default and
portable warning flags.
If you need any help, I would be very pleased to contribute.

J. Bedouet


>Michael Jackson wrote:
>>
>> On Nov 22, 2008, at 1:13 PM, Robert Dailey wrote:
>>
>>> So it seems that this issue has come up before and it is an obvious
>>> feature to implement. In the meantime, can someone offer me the code
>>> for a macro I can use to easily and portably set warning levels?
>>>
>>> Thanks
>>
>>
>> pseudo code
>>
>> macro(set_warning_level level)
>>
>> if (MSVC)
>> # Set msvc type warnings
>> SET (CXX_FLAGS ${CXX_FLAGS} [your warnings here])
>>
>> elseif(GCC)
>> # set gcc type warnings
>> SET (CXX_FLAGS ${CXX_FLAGS} [your warnings here])
>>
>> else()
>> # we don't know this compiler
>> message(STATUS "Warning levels have not been defined for this compiler")
>>
>> endif()
>>
>> endmacro(set_warning_level level)
>>
>
>When this is done in CMake, that information will go into the
>Modules/Platform files.   So, it might be best to come up with something
>that uses the same idea as that.
>
>   INCLUDE(MyPlatform/${CMAKE_SYSTEM_NAME}-${CMAKE_CXX_COMPILER_ID}-CXX
>OPTIONAL )
>
>Put MyPlatform into the CMAKE_MODULE_PATH, then create platform files in
>MyPlatform/Linux-Intel-C.cmake
>
>set(${CMAKE_CXX_COMPILER_ID}-CXX-WARNING1 -W1)
>
>Then have the macro just add the specified warning variable.  If someone
>works out all the names, we can then move this stuff into CMake CVS.
>
>-Bill
>
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