Re: [edk2-devel] [PATCH] OvmfPkg/X86QemuLoadImageLib: add dummy assignment to work around GCC

["Laszlo Ersek" <lersek@redhat.com>]

On 03/25/20 10:12, Ard Biesheuvel wrote:
> GCC 4.8 or 4.9 may throw the following error when building OVMF:
> 
>   Edk2/OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.c:
>       In function ‘QemuLoadKernelImage’:
>   Edk2/OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.c:416:30:
>       error: ‘CommandLine’ may be used uninitialized in this function
>                                                [-Werror=maybe-uninitialized]
>         UnicodeSPrintAsciiFormat (
>         cc1: all warnings being treated as errors
> 
> This is due to the fact that older GCCs fail to infer that CommandLine is
> never actually used unless it has been assigned. So add a redundant NULL
> assignment to help these older GCCs understand this.
> 
> Link: https://bugzilla.tianocore.org/show_bug.cgi?id=2630
> Fixes: 7c47d89003a6f ("OvmfPkg: implement QEMU loader library for X86 with ...")
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.c b/OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.c
> index c5bd6862b265..52b14a4462d8 100644
> --- a/OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.c
> +++ b/OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.c
> @@ -291,6 +291,11 @@ QemuLoadKernelImage (
>    CHAR8                     *CommandLine;
>    UINTN                     InitrdSize;
>  
> +  //
> +  // Redundant assignment to work around GCC48/GCC49 limitations.
> +  //
> +  CommandLine = NULL;
> +
>    //
>    // Load the image. This should call back into the QEMU EFI loader file system.
>    //
> 

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thanks,
Laszlo