Re: [PATCH v6 01/19] configure, meson: override C compiler for cmake

[Paolo Bonzini <pbonzini@redhat.com>]

On 2/18/22 04:40, Jag Raman wrote:
> 
> 
>> On Feb 17, 2022, at 7:09 AM, Peter Maydell <peter.maydell@linaro.org> wrote:
>>
>> On Thu, 17 Feb 2022 at 07:56, Jagannathan Raman <jag.raman@oracle.com> wrote:
>>>
>>> The compiler path that cmake gets from meson is corrupted. It results in
>>> the following error:
>>> | -- The C compiler identification is unknown
>>> | CMake Error at CMakeLists.txt:35 (project):
>>> | The CMAKE_C_COMPILER:
>>> | /opt/rh/devtoolset-9/root/bin/cc;-m64;-mcx16
>>> | is not a full path to an existing compiler tool.
>>>
>>> Explicitly specify the C compiler for cmake to avoid this error
>>
>> This sounds like a bug in Meson. Is there a Meson bug report
>> we can reference in the commit message here ?
> 
> Hi Peter,
> 
> This issue reproduces with the latest meson [1] also.

0.60.0 or more recent versions should have a fix, which would do exactly 
what this patch does: do not define CMAKE_C_COMPILER_LAUNCHER, and place 
the whole binaries.c variable in CMAKE_C_COMPILER.  What are the 
contents of the genrated CMakeMesonToolchainFile.cmake and 
CMakeCache.txt files, without and with your patch?

> I noticed the following about the “binaries” section [2]. The manual
> says meson could pass the values in this section to find_program [3].
> As such I’m wondering if it’s OK to set compiler flags in this section
> because find_program doesn’t seem to accept any compiler flags.

The full quote of the manual is "These can be used internally by Meson, 
or by the find_program function", and the C compiler variable "c" is in 
the former category.

There is an important difference between the flags in "binaries" and 
those in "built-in options". What is in "binaries" is used when 
requesting e.g. the compiler search path, while what is in "built-in 
options" is not.  So options like "-m32" are definitely part of 
"binaries", not "built-in options":

     $ gcc --print-multi-os-directory
     ../lib64
     $ gcc -m32 --print-multi-os-directory
     ../lib

Paolo