Re: [PATCH 2/9] tests/tcg: improve check for working cross compilers

[Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>]

On 9/10/26 11:14 AM, Alex Bennée wrote:
> From: Daniel P. Berrangé <berrange@redhat.com>
> 
> When it finds a cross compiler, tests/tcg/meson.build tries
> building test_cc.c to validate that the compiler works. This
> includes "stdint.h" as a witness for working C library, however,
> that is not a good choice as it can be provided by the toolchain
> alone:
> 
>    $ rpm -ql gcc-s390x-linux-gnu  | grep /stdint.h
>    /usr/lib/gcc/s390x-linux-gnu/16/include/stdint.h
> 
> As a result, if you install the s390x GCC cross compiler, but
> not any C library, meson decides to use the host compiler instead
> of the container:
> 
>      cc for aarch64-softmmu          : aarch64-linux-gnu-gcc (from 'debian-all-test-cross' container)
>      cc for loongarch64-softmmu      : loongarch64-unknown-linux-gnu-gcc (from 'debian-loongarch-cross' container)
>      cc for riscv64-softmmu          : riscv64-linux-gnu-gcc (from 'debian-all-test-cross' container)
>      cc for s390x-softmmu            : s390x-linux-gnu-gcc
>      cc for x86_64-softmmu           : x86_64-linux-gnu-gcc (from 'debian-amd64-cross' container)
> 
> Eventually this results in failure to run 'make check':
> 
> [33/40] Generating tests/tcg/s390x-softmmu-hello with a custom command
> FAILED: [code=1] tests/tcg/s390x-softmmu-hello.test
> /usr/bin/s390x-linux-gnu-gcc /home/berrange/src/virt/qemu/tests/tcg/multiarch/system/hello.c -o tests/tcg/s390x-softmmu-hello.test -static -MMD -MF tests/tcg/s390x-softmmu-hello.d -Wall -Werror -O0 -g -fno-strict-aliasing -nostdlib -ffreestanding -Wa,--noexecstack -I /home/berrange/src/virt/qemu/tests/tcg/s390x/system/../../minilib /home/berrange/src/virt/qemu/tests/tcg/s390x/system/../../minilib/printf.c -I /home/berrange/src/virt/qemu/include/hw/s390x/ipl -march=z13 ../tests/tcg/s390x/system/../head64.S ../tests/tcg/s390x/system/../console.c
> In file included from ../tests/tcg/s390x/system/../console.c:8:
> ../tests/tcg/s390x/system/../../../../pc-bios/s390-ccw/sclp.c:11:10: fatal error: string.h: No such file or directory
>     11 | #include <string.h>
>        |          ^~~~~~~~~~
> compilation terminated.
> 
> Adding more include files to the test program ensures the
> meson probe makes a better decision.
> 
> Fixes: e5d084d622b1 (tests/tcg/meson.build: check host cross cc is working)
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> Message-ID: <20260910100120.2076092-1-berrange@redhat.com>
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> ---
>   tests/tcg/test_cc.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/tests/tcg/test_cc.c b/tests/tcg/test_cc.c
> index d3614a01fe6..fafee055b40 100644
> --- a/tests/tcg/test_cc.c
> +++ b/tests/tcg/test_cc.c
> @@ -1,7 +1,11 @@
>   /* SPDX-License-Identifier: GPL-2.0-or-later */
>   
> -/* Include a standard header to make sure cross compiler provides them */
> +/* Use some standard headers to ensure the cross compiler provides them */
>   #include <stdint.h>
> +#include <string.h>
> +#include <stdbool.h>
> +#include <stddef.h>
> +#include <stdio.h>
>   
>   int main(void)
>   {

Ideally, we should do separate tests for system vs user tests.
System ones are always compiled with -ffreestanding, while user ones 
should provide a C library.

 From this standard:

https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2338r3.html
```
A freestanding C implementation is required to provide the entirety of 
the following headers:

<float.h>
<iso646.h>
<limits.h>
<stdalign.h>
<stdarg.h>
<stdbool.h>
<stddef.h>
<stdint.h>
<stdnoreturn.h>
Most of <string.h> is required (strdup, strndup, strcoll, strxfrm, and 
strerror are excluded). This includes strtok, which requires global data.
```

Maybe for now we can just remove stdio.h from current patch, as it's not 
supposed to be provided in a freestanding environment.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>

Regards,
Pierrick