[CMake] Toolchains and CMAKE_FORCE_C_COMPILER in 3.5

[Chuck Atkins]

Hi Thibault,

Can you post your toolchain file?

- Chuck

On Tue, Feb 9, 2016 at 9:10 AM, Thibault Genessay <tibogens at gmail.com>
wrote:

> Hi,
>
> I'm a long time user of CMake (and huge fan of it) but newly registered on
> this list, so please forgive me if I have missed something regarding the
> new 3.5 series.
>
> I use CMake with the GCC ARM Embedded compiler (
> https://launchpad.net/gcc-arm-embedded) to cross-compile my project
> (Windows host, STM32 target, MinGW binutils). Like many users (all?) I had
> to create a toolchain file because CMake doesn't support this
> compiler/setup out of the box. I have taken inspiration from the many
> Google hits and had a working setup until 3.5. This setup relied on the
> CMAKE_FORCE_<lang>_COMPILER macros.
>
> I installed 3.5 and the build broke, CMake complaining that this macro was
> deprecated and should not be used because of the many improvements on the
> compiler detection side. OK, so I removed the offending lines, simply
> setting the CMAKE_C_COMPILER variable to the compiler's executable ... and
> suddenly I remember why I did use this FORCE hack in the first place: CMake
> tells me my compiler is broken because it cannot compile a test program
> (undefined symbol: _exit). This is somehow correct, as I compile for bare
> metal and I am providing the _exit function in my code. This is a
> misunderstanding the CMAKE_FORCE_C_COMPILER works around by simply saying
> "believe me, this compiler works".
>
> Now I am left without many options: I can't use the FORCE hack, and I
> can't convince CMake my compiler is OK. I am very open to redesign my
> toolchain file, or use a stock one from CMake, or whatever this takes, but
> I simply do not know how to proceed. Actually, I feel my current toolchain
> file, although functional, is not "clean" but never had enough time to do
> it. Now that it's a blocking issue, I do have time :)
>
> I rolled back to 3.4 and things work so I'm safe for now. But I would be
> very glad if somebody knew more about this specific problem, or this
> compiler, or toolchain file writing in general. I would love to write a
> "stock" toolchain file for this compiler but I simply do not know enough
> (nor I can find enough up-to-date documentation).
>
> Thanks for reading,
> Cheers
>
> Thibault
>
>
>
>
>
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