[cmake-developers] [CMake] Toolchains and CMAKE_FORCE_C_COMPILER in 3.5

[James Crosby]

> On 17 Feb 2016, at 14:33, Brad King <brad.king at kitware.com> wrote:
>
> One could look at adding hooks to the compiler id logic to add alternatives
> provided by the toolchain file.  Or, we could provide a way to set the compiler
> id but not also skip other checks.  In the worst case such a company could modify
> their CMake for use with such a toolchain.  I do not consider this a blocking
> issue for deprecating CMakeForceCompiler.

I think allowing the compiler id to be set might be enough – in the case that
the compiler is completely unknown, functionality is anyway going to be limited
to what the user implements/supports themselves.


> It is not just a check that linking works.  CMake actually encodes string
> literals in the compiled binary and parses it to extract them.  This allows
> us to extract information about the compiler target architecture and compiler
> capabilities.  OTOH we may not actually have to link to achieve this.
>
> Perhaps we could have a setting in a toolchain file like
>
>    set(CMAKE_TRY_COMPILE_NO_LINK 1)
>
> that tells CMake to use add_library(STATIC) instead of add_executable()
> in its generated try_compile projects.  That would avoid linking through
> the toolchain.

OK this makes a lot more sense to me now (I should have looked at the code
first ;). It seems like the option to link a static library would have all the
benefits of getting information out of the compiler itself (instead of
duplicating it in toolchain files), without having to be able to produce a
linkable executable.


> Meanwhile I've de-deprecated the module for the 3.5 release:

Thanks, this will be useful breathing space!


James

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