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

[Jag Raman <jag.raman@oracle.com>]

> On Feb 18, 2022, at 7:13 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> 
> 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’ll checkout what’s going on at my end. But the issue reproduces with
meson 0.61 from what I can tell:
# ../configure --target-list=x86_64-softmmu --enable-debug --enable-vfio-user-server;
The Meson build system
Version: 0.61.2
…
…
| /opt/rh/devtoolset-9/root/usr/bin/cc;-m64;-mcx16

| is not a full path to an existing compiler tool.


Concerning the generated files, I see the following in CMakeMesonToolchainFile.cmake:
Without patch: set(CMAKE_C_COMPILER "/opt/rh/devtoolset-9/root/usr/bin/cc" "-m64" "-mcx16”)
With patch: set(CMAKE_C_COMPILER "cc" "-m64" "-mcx16")

> 
>> 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

Do you know if the “host_machine” section in cross build
definition file [1] would be any help here?

[1]: https://mesonbuild.com/Cross-compilation.html#machine-entries

--
Jag

> 
> Paolo