[Xen-devel] Re: [Xen-changelog] Make it possible to run valgrind on code linked with the libxc libraries.

[Muli Ben-Yehuda <mulix@xxxxxxxxx>]

On Tue, Nov 22, 2005 at 06:20:06PM +0000, Xen patchbot -unstable wrote:
> diff -r c1c8da6f2afe -r 602aefe7bd48 tools/libxc/xg_private.h
> --- a/tools/libxc/xg_private.h        Mon Nov 21 18:08:44 2005
> +++ b/tools/libxc/xg_private.h        Tue Nov 22 15:31:16 2005
> @@ -15,6 +15,16 @@
>  
>  #include <xen/linux/privcmd.h>
>  #include <xen/memory.h>
> +
> +/* valgrind cannot see when a hypercall has filled in some values.  For this
> +   reason, we must zero the dom0_op_t instance before a call, if using
> +   valgrind.  */
> +#ifdef VALGRIND
> +#define DECLARE_DOM0_OP dom0_op_t op; memset(&op, 0, sizeof(op))
> +#else
> +#define DECLARE_DOM0_OP dom0_op_t op
> +#endif

This is pretty ugly IMHO. Also, if someone does

if (foo)
        bla;
else
        DECLARE_DOM0_OP;

it breaks.

Is the micro-optimization of not initializing the structures to 0
worth it? I really doubt it. But if yes, please at least do something
like

#ifdef VALGRIND
#define DECLARE_DOM0_OP(name) dom0_op_t name = {
        .cmd = 0,
        .interface_version = 0, 
        .pad = { 0 }
}
#else
#define #define DECLARE_DOM0_OP(name) dom0_op_t name;
#endif

Cheers,
Muli
-- 
Muli Ben-Yehuda
http://www.mulix.org | http://mulix.livejournal.com/


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