Re: [Qemu-devel] [PATCH] migration: Fix compiler warning ('caps' may be used uninitialized)

[Paolo Bonzini <pbonzini@redhat.com>]

Il 29/09/2013 17:41, Stefan Weil ha scritto:
> The QEMU buildbot default_i386_debian_6_0 shows this warning:
> 
>   CC    migration.o
> migration.c: In function 'qmp_query_migrate_capabilities':
> migration.c:149: warning:
>  'caps' may be used uninitialized in this function
> 
> While changing this code, I also replaced g_malloc0
> by the type safe g_new0.
> 
> Signed-off-by: Stefan Weil <sw@weilnetz.de>
> ---
> 
> Buildbot URL:
> http://buildbot.b1-systems.de/qemu/builders/default_i386_debian_6_0/builds/775/steps/compile/logs/stdio
> 
>  migration.c |   12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/migration.c b/migration.c
> index 200d404..8dcb6ce 100644
> --- a/migration.c
> +++ b/migration.c
> @@ -145,17 +145,15 @@ uint64_t migrate_max_downtime(void)
>  
>  MigrationCapabilityStatusList *qmp_query_migrate_capabilities(Error **errp)
>  {
> -    MigrationCapabilityStatusList *head = NULL;
> -    MigrationCapabilityStatusList *caps;
> +    MigrationCapabilityStatusList *head =
> +        g_new0(MigrationCapabilityStatusList, 1);
> +    MigrationCapabilityStatusList *caps = head;
>      MigrationState *s = migrate_get_current();
>      int i;
>  
>      for (i = 0; i < MIGRATION_CAPABILITY_MAX; i++) {
> -        if (head == NULL) {
> -            head = g_malloc0(sizeof(*caps));
> -            caps = head;
> -        } else {
> -            caps->next = g_malloc0(sizeof(*caps));
> +        if (i > 0) {
> +            caps->next = g_new0(MigrationCapabilityStatusList, i);
>              caps = caps->next;
>          }
>          caps->value =
> 

What about

    MigrationCapabilityStatusList *head = NULL;
    MigrationCapabilityStatusList **p_tail = &head;
    MigrationState *s = migrate_get_current();
    int i;

    for (i = 0; i < MIGRATION_CAPABILITY_MAX; i++) {
        MigrationCapabilityStatusList *caps = g_malloc0(sizeof(*caps));
        caps->value =
            ...
        *p_next = caps;
        p_next = &caps->next;
    }