Re: [PATCH for-9.0] meson.build: Disable -fzero-call-used-regs on OpenBSD

[Thomas Huth <thuth@redhat.com>]

On 11/04/2024 14.08, Thomas Huth wrote:
> QEMU currently does not work on OpenBSD since the -fzero-call-used-regs

That should be "OpenBSD 7.5" ... older versions are fine since they are 
using an older version of Clang that does not have -fzero-call-used-regs 
yet, I think.

  Thomas


> option that we added to meson.build recently does not work with the
> "retguard" extension from OpenBSD's Clang. Thus let's disable the
> -fzero-call-used-regs here until there's a better solution available.
> 
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2278
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>   Note: Given that we're close to the release, I think the host_os check
>   is the best we can do ... the problem does not seem to trigger in all
>   functions, only if certain registers are used by the compiler, so a
>   more sophisticated check here seems to be too fragile to me right now.
> 
>   meson.build | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/meson.build b/meson.build
> index c9c3217ba4..91a0aa64c6 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -562,7 +562,11 @@ hardening_flags = [
>   #
>   # NB: Clang 17 is broken and SEGVs
>   # https://github.com/llvm/llvm-project/issues/75168
> -if cc.compiles('extern struct { void (*cb)(void); } s; void f(void) { s.cb(); }',
> +#
> +# NB2: This clashes with the "retguard" extension of OpenBSD's Clang
> +# https://gitlab.com/qemu-project/qemu/-/issues/2278
> +if host_os != 'openbsd' and \
> +   cc.compiles('extern struct { void (*cb)(void); } s; void f(void) { s.cb(); }',
>                  name: '-fzero-call-used-regs=used-gpr',
>                  args: ['-O2', '-fzero-call-used-regs=used-gpr'])
>       hardening_flags += '-fzero-call-used-regs=used-gpr'