Re: [Qemu-devel] [PATCH] qom: avoid reporting errors for NULL error object

[Marc-André Lureau]

Hi

On Mon, Nov 19, 2018 at 5:59 PM Daniel P. Berrangé <address@hidden> wrote:
>
> When debugging QEMU it is often useful to put a breakpoint on the
> error_setg_internal method impl.
>
> Unfortunately the object_property_add / object_class_property_add
> methods call object_property_find / object_class_property_find methods
> to check if a property exists already before adding the new property.
>
> As a result there are a huge number of calls to error_setg_internal
> on startup of most QEMU commands, making it very painful to set a
> breakpoint on this method.
>
> This puts a minor optimization on the code so that we avoid calling
> error_setg() when errp is NULL. Functionally there's no difference
> since error_setg() is a no-op when errp is NULL, but this lets us
> use breakpoints in GDB in a practical way.
>
> Signed-off-by: Daniel P. Berrangé <address@hidden>

Or maybe change the error_setg* macros? After all, if errp is NULL,
it's an error qemu can handle.

> ---
>  qom/object.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/qom/object.c b/qom/object.c
> index 547dcf97c3..ddd5e7a30e 100644
> --- a/qom/object.c
> +++ b/qom/object.c
> @@ -1087,7 +1087,12 @@ ObjectProperty *object_property_find(Object *obj, 
> const char *name,
>          return prop;
>      }
>
> -    error_setg(errp, "Property '.%s' not found", name);
> +    /* Optimized to avoid calling error_setg if errp == NULL
> +     * otherwise every property add call hits error_setg
> +     * making it impratical to set breakpoints in GDB */
> +    if (errp) {
> +        error_setg(errp, "Property '.%s' not found", name);
> +    }
>      return NULL;
>  }
>
> @@ -1133,7 +1138,10 @@ ObjectProperty *object_class_property_find(ObjectClass 
> *klass, const char *name,
>      }
>
>      prop = g_hash_table_lookup(klass->properties, name);
> -    if (!prop) {
> +    /* Optimized to avoid calling error_setg if errp == NULL
> +     * otherwise every property add call hits error_setg
> +     * making it impratical to set breakpoints in GDB */
> +    if (!prop && errp) {
>          error_setg(errp, "Property '.%s' not found", name);
>      }
>      return prop;
> --
> 2.19.1
>
>


-- 
Marc-André Lureau