linux-kernel - Re: [PATCH] KVM: selftests: Assert that vasprintf() is successful

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Date:   Thu, 14 Sep 2023 10:02:28 +0200
From:   Andrew Jones <ajones@...tanamicro.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Haibo Xu <haibo1.xu@...el.com>,
        Anup Patel <anup@...infault.org>
Subject: Re: [PATCH] KVM: selftests: Assert that vasprintf() is successful

On Wed, Sep 13, 2023 at 06:06:36PM -0700, Sean Christopherson wrote:
> Assert that vasprintf() succeeds as the "returned" string is undefined
> on failure.  Checking the result also eliminates the only warning with
> default options in KVM selftests, i.e. is the only thing getting in the
> way of compile with -Werror.
> 
>   lib/test_util.c: In function ‘strdup_printf’:
>   lib/test_util.c:390:9: error: ignoring return value of ‘vasprintf’
>   declared with attribute ‘warn_unused_result’ [-Werror=unused-result]
>   390 |         vasprintf(&str, fmt, ap);
>       |         ^~~~~~~~~~~~~~~~~~~~~~~~
> 

Oh, darn. My compilers didn't report that or I would have fixed it.

> Don't bother capturing the return value, allegedly vasprintf() can only
> fail due to a memory allocation failure.
> 
> Fixes: dfaf20af7649 ("KVM: arm64: selftests: Replace str_with_index with strdup_printf")
> Cc: Andrew Jones <ajones@...tanamicro.com>
> Cc: Haibo Xu <haibo1.xu@...el.com>
> Cc: Anup Patel <anup@...infault.org>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
> 
> I haven't actually run the relevant tests, someone should probably do so on
> ARM and/or RISC-V to make sure I didn't do something stupid.

Done for both.

Reviewed-by: Andrew Jones <ajones@...tanamicro.com>
Tested-by: Andrew Jones <ajones@...tanamicro.com>

Thanks,
drew

> 
>  tools/testing/selftests/kvm/lib/test_util.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
> index 3e36019eeb4a..5d7f28b02d73 100644
> --- a/tools/testing/selftests/kvm/lib/test_util.c
> +++ b/tools/testing/selftests/kvm/lib/test_util.c
> @@ -387,7 +387,7 @@ char *strdup_printf(const char *fmt, ...)
>  	char *str;
>  
>  	va_start(ap, fmt);
> -	vasprintf(&str, fmt, ap);
> +	TEST_ASSERT(vasprintf(&str, fmt, ap) >= 0, "vasprintf() failed");
>  	va_end(ap);
>  
>  	return str;
> 
> base-commit: 0bb80ecc33a8fb5a682236443c1e740d5c917d1d
> -- 
> 2.42.0.283.g2d96d420d3-goog
>