[PATCH] Fix usage of talloc_steal

[Lukas Slebodnik]

ehlo,

talloc_steal is a macro around function _talloc_steal_loc
and returns the pointer that you pass it. It does not have any failure modes.

If the output value is ignored there are compiler warnings.

Example of warning
src/util/util.c:503:164: warning: expression result unused [-Wunused-value]
        ({ __typeof__(internal_ctx) __talloc_steal_ret = (__typeof__(internal_ctx))_talloc_steal_loc((table),(internal_ctx), "../sssd/src/util/util.c" ":" "503"); __talloc_steal_ret; });
                                                                                                                                                                   ^~~~~~~~~~~~~~~~~~
1 warning generated.

I am opened to better solution of this warning.

LS

[Simo Sorce]

On Sat, 10 Jan 2015 18:12:26 +0100
Lukas Slebodnik  wrote:
> ehlo,
>
> talloc_steal is a macro around function _talloc_steal_loc
> and returns the pointer that you pass it. It does not have any
> failure modes.
>
> If the output value is ignored there are compiler warnings.
>
> Example of warning
> src/util/util.c:503:164: warning: expression result unused
> [-Wunused-value] ({ __typeof__(internal_ctx) __talloc_steal_ret =
> (__typeof__(internal_ctx))_talloc_steal_loc((table),(internal_ctx),
> "../sssd/src/util/util.c" ":" "503"); __talloc_steal_ret; });
> ^~~~~~~~~~~~~~~~~~ 1 warning generated.
>
> I am opened to better solution of this warning.

Maybe always assign to the variable being stolen ?

I do not remember if there is any case when a steal may cause the
pointer to change (probably not) but the assignment would be safe and
the compiler can optimize it out if the variable is not used further or
internally no assignment ever happens.

Simo.

[Pavel Březina]

On 01/10/2015 06:12 PM, Lukas Slebodnik wrote:
> ehlo,
>
> talloc_steal is a macro around function _talloc_steal_loc
> and returns the pointer that you pass it. It does not have any failure modes.
>
> If the output value is ignored there are compiler warnings.
>
> Example of warning
> src/util/util.c:503:164: warning: expression result unused [-Wunused-value]
>          ({ __typeof__(internal_ctx) __talloc_steal_ret = (__typeof__(internal_ctx))_talloc_steal_loc((table),(internal_ctx), "../sssd/src/util/util.c" ":" "503"); __talloc_steal_ret; });
>                                                                                                                                                                     ^~~~~~~~~~~~~~~~~~
> 1 warning generated.
>
> I am opened to better solution of this warning.
>
> LS

I would ignore this warning. Ignoring return value has lots of use cases.

[Lukas Slebodnik]

On (12/01/15 13:27), Pavel Březina wrote:
> On 01/10/2015 06:12 PM, Lukas Slebodnik wrote:
> > ehlo,
> >
> > talloc_steal is a macro around function _talloc_steal_loc
> > and returns the pointer that you pass it. It does not have any failure modes.
> >
> > If the output value is ignored there are compiler warnings.
> >
> > Example of warning
> > src/util/util.c:503:164: warning: expression result unused [-Wunused-value]
> >         ({ __typeof__(internal_ctx) __talloc_steal_ret = (__typeof__(internal_ctx))_talloc_steal_loc((table),(internal_ctx), "../sssd/src/util/util.c" ":" "503"); __talloc_steal_ret; });
> >                                                                                                                                                                    ^~~~~~~~~~~~~~~~~~
> > 1 warning generated.
> >
> > I am opened to better solution of this warning.
> >
> > LS
>
> I would ignore this warning. Ignoring return value has lots of use cases.

Actually it is not ignoring returned value from function (-Wunused-result)
because talloc_steal is macro and you are ignoring unused value
in expanded macro (-Wunused-value)

It could be reason why Jakub did not noticed warning
https://lists.fedorahosted.org/pipermail/sssd-devel/2015-January/022195.html
He uses clang as well.

LS