Re: [PATCH v2] hw/i386/amd_iommu: Fix maybe-uninitialized error with GCC 12

[Philippe Mathieu-Daudé]

On 21/3/22 15:33, Paolo Bonzini wrote:
> Be more explicit that the loop must roll at least once.  Avoids the
> following warning:
>
>    FAILED: libqemu-x86_64-softmmu.fa.p/hw_i386_amd_iommu.c.o
>    In function 'pte_get_page_mask',
>        inlined from 'amdvi_page_walk' at hw/i386/amd_iommu.c:945:25,
>        inlined from 'amdvi_do_translate' at hw/i386/amd_iommu.c:989:5,
>        inlined from 'amdvi_translate' at hw/i386/amd_iommu.c:1038:5:
>    hw/i386/amd_iommu.c:877:38: error: 'oldlevel' may be used uninitialized 
> [-Werror=maybe-uninitialized]
>      877 |     return ~((1UL << ((oldlevel * 9) + 3)) - 1);
>          |                      ~~~~~~~~~~~~~~~~^~~~
>    hw/i386/amd_iommu.c: In function 'amdvi_translate':
>    hw/i386/amd_iommu.c:906:41: note: 'oldlevel' was declared here
>      906 |     unsigned level, present, pte_perms, oldlevel;
>          |                                         ^~~~~~~~
>    cc1: all warnings being treated as errors
>
> Having:
>
>    $ gcc --version
>    gcc (Debian 12-20220313-1) 12.0.1 20220314 (experimental)
>
> Reported-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   hw/i386/amd_iommu.c | 7 ++-----
>   1 file changed, 2 insertions(+), 5 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

Thanks!