Re: [Qemu-devel] [PATCH] use qemu_malloc and friends consistently

[jcd@tribudubois.net]

Hi Kevin,

Thanks for pointing this. I guess it just sounds strange to me that somebody would want to alloc 0 bytes. But why not ...

I guess that if pattern_count/count is set to 0 we can just avoid the all processing of malloc/memset/memcmp/free anyway.

Would you be ok with something like:

if (Pflag && pattern_count) {

instead of: 

if (Pflag) {

JC

----- Mail Original -----
De: "Kevin Wolf" <kwolf@redhat.com>
À: "Jean-Christophe Dubois" <jcd@tribudubois.net>
Cc: qemu-devel@nongnu.org, "malc" <av1474@comtv.ru>
Envoyé: Vendredi 29 Mai 2009 10h42:38 GMT +01:00 Amsterdam / Berlin / Berne / Rome / Stockholm / Vienne
Objet: Re: [Qemu-devel] [PATCH] use qemu_malloc and friends consistently

Jean-Christophe Dubois schrieb:
> qemu_malloc, qemu_free and friends are not used consistently in the qemu 
> source code.
> 
> This is a first attempt to use these oveloaded functions consistently all over 
> the place instead of the default glibc versions.
> 
> Signed-off-by: Jean-Christophe DUBOIS <jcd@tribudubois.net>

[...]

> diff -rNu qemu.org/qemu-io.c qemu/qemu-io.c
> --- qemu.org/qemu-io.c	2009-05-16 17:57:27.000000000 +0200
> +++ qemu/qemu-io.c	2009-05-18 23:48:23.000000000 +0200
> @@ -311,14 +311,14 @@
>  	}
>  
>  	if (Pflag) {
> -		void* cmp_buf = malloc(pattern_count);
> +		void* cmp_buf = qemu_malloc(pattern_count);
>  		memset(cmp_buf, pattern, pattern_count);
>  		if (memcmp(buf + pattern_offset, cmp_buf, pattern_count)) {
>  			printf("Pattern verification failed at offset %lld, "
>  				"%d bytes\n",
>  				(long long) offset + pattern_offset, pattern_count);
>  		}
> -		free(cmp_buf);
> +		qemu_free(cmp_buf);
>  	}
>  
>  	if (qflag)
> @@ -465,14 +465,14 @@
>  	}
>  
>  	if (Pflag) {
> -		void* cmp_buf = malloc(count);
> +		void* cmp_buf = qemu_malloc(count);
>  		memset(cmp_buf, pattern, count);
>  		if (memcmp(buf, cmp_buf, count)) {
>  			printf("Pattern verification failed at offset %lld, "
>  				"%d bytes\n",
>  				(long long) offset, count);
>  		}
> -		free(cmp_buf);
> +		qemu_free(cmp_buf);
>  	}
>  
>  	if (qflag)

Since recently qemu_malloc behaves differently from malloc with size =
0. This isn't allowed any more with qemu_malloc. So you need to check
for pattern_count == 0 and either print an error message or malloc a
different size, e.g. 1. I'm sure we don't want qemu-io to abort() in
such a case.

Or we could start over with a lengthy discussion about fixing qemu_malloc...

Kevin