Re: [Qemu-devel] [PATCH] Permit zero-sized qemu_malloc() & friends

[Gerd Hoffmann]

> diff --git a/qemu-malloc.c b/qemu-malloc.c
> index 295d185..aeeb78b 100644
> --- a/qemu-malloc.c
> +++ b/qemu-malloc.c
> @@ -44,22 +44,12 @@ void qemu_free(void *ptr)
>
>   void *qemu_malloc(size_t size)
>   {
> -    if (!size) {
> -        abort();
> -    }
> -    return oom_check(malloc(size));
> +    return oom_check(malloc(size ? size : 1));
>   }

You might want to have a 'static uint8_t zero_length_malloc[0]' and 
return that instead of the magic cookie '1'.  Makes the code more 
readable IMHO and you'll also have symbol in gdb when debugging qemu.

Even more advanced:  Make zero_length_malloc page-sized and 
page-aligned, then munmap int, so dereferencing it actually traps.

>   void *qemu_realloc(void *ptr, size_t size)
>   {
> +    return oom_check(realloc(ptr, size ? size : 1));

qemu_realloc(qemu_malloc(0), 42);

should better work correctly ...

Likewise qemu_free(qemu_malloc(0));

cheers,
  Gerd