Re: [PATCH 4/9] util/oslib-win32: Return NULL on qemu_try_memalign() with zero size

[Richard Henderson]

On 2/26/22 08:07, Peter Maydell wrote:
> Currently if qemu_try_memalign() is asked to allocate 0 bytes, we assert.
> Instead return NULL; this is in line with the posix_memalign() API,
> and is valid to pass to _aligned_free() (which will do nothing).
>
> This change is a preparation for sharing the qemu_try_memalign()
> code between Windows and POSIX -- at the moment only the Windows
> version has the assert that size != 0.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>   util/oslib-win32.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/util/oslib-win32.c b/util/oslib-win32.c
> index 05857414695..8c1c64719d7 100644
> --- a/util/oslib-win32.c
> +++ b/util/oslib-win32.c
> @@ -48,13 +48,16 @@ void *qemu_try_memalign(size_t alignment, size_t size)
>   {
>       void *ptr;
>   
> -    g_assert(size != 0);
>       if (alignment < sizeof(void *)) {
>           alignment = sizeof(void *);
>       } else {
>           g_assert(is_power_of_2(alignment));
>       }
> -    ptr = _aligned_malloc(size, alignment);
> +    if (size) {
> +        ptr = _aligned_malloc(size, alignment);
> +    } else {
> +        ptr = NULL;
> +    }

Oh, should we set errno to something here?
Otherwise a random value will be used by qemu_memalign.


r~

>       trace_qemu_memalign(alignment, size, ptr);
>       return ptr;
>   }