[cmake-developers] c++ feature detection and usage requirements

[Stephen Kelly]

Brad King wrote:

> On 08/30/2013 08:02 AM, Stephen Kelly wrote:
>> It turns out that in order to do this, the compiler features would
>> have to be listed independently of Modules/Compiler/${ID}.cmake.
>> Otherwise I wouldn't be able to check the MSVC features while using GNU.
>> 
>> Maybe they should be listed in
>> Modules/CompilerFeatures/${ID}-${LANG}.cmake instead?
> 
> Why do you need to check features of a compiler not currently enabled?
> Without being enabled we don't even know what version of the other
> compiler to check.

CMake has the information for all compilers, and the idea was to use that 
information to generate a header for use with all of them.

Stephen Kelly wrote:
> The header file would have the preprocessor tests and version checks for
> the known compilers. That is, the generated header file would be the same
> on all platforms, and would look something like qcompilerdetection.h, but
> with a customizable prefix for the macros.

 http://thread.gmane.org/gmane.comp.programming.tools.cmake.devel/6726/focus=7655

However, thinking about it again, I think you're right that that is not 
necessary. The built package and generated header is compiler/platform 
specific anyway, unlike qcompilerdetection.h, which is a source file 
identical in the packages for all platforms.

> 
> I thought the idea was to specify in target_compiler_features the
> features needed so they would be published in the target interface.
> Then whatever compiler is used can have its feature set tested against
> the requirements.  This would work both in-project and in consumers, no?

Yes, I went on something of a tangent here.

Thanks,

Steve.