diff mbox

Warn about return with a void expression with -Wreturn-type.

Message ID CALvMQwTU0eNPP+=E+jo4uE4Znq+5_GE0N=aTBY7imZj5Lu=QEg@mail.gmail.com
State New
Headers show

Commit Message

Marcin Baczyński June 1, 2016, 6:59 p.m. UTC 
2016-06-01 19:03 GMT+02:00 Martin Sebor <msebor@gmail.com>:
>
> On 06/01/2016 10:39 AM, Jakub Jelinek wrote:
>>
>> On Wed, Jun 01, 2016 at 02:44:22PM +0200, Marcin Baczyński wrote:
>>>
>>> On 1 Jun 2016 14:07, "Jakub Jelinek" <jakub@redhat.com> wrote:
>>>>
>>>>
>>>> On Wed, Jun 01, 2016 at 01:55:04PM +0200, Marcin Baczyński wrote:
>>>>>
>>>>> PR c/48116.
>>>>>
>>>>> Botstrapped and tested on x86_64-pc-linux-gnu.
>>>>>
>>>>> gcc/ChangeLog:
>>>>>
>>>>>     * c/c-typeck.c (c_finish_return): emit warning about return with a
>>>>>      void expression in a function returning void if warn_return_type.
>>>>
>>>>
>>>> This is a GNU extension, so I fail to see why you should warn.
>>>
>>>
>>> The bug is on the easyhacks list, I thought it would be a good place to
>>> start digging into the GCC code base.
>>
>>
>> First of all, I'm not the C FE maintainer, so these are just IMHO comments,
>> the maintainers might have different opinion.
>>
>>> Do you have any suggestions for better things to start with?
>
>
> Since you've done a lot of work on this bug already I think it
> would be worthwhile to see it through to completion.  Given that,
> as Jakub mentioned, the absence of the warning in permissive mode
> (i.e. without -Wpedantic) is a GCC extension to C, it would be
> helpful to mention it in the manual (doing so would resolve the
> submitter's complaint that the -Wreturn-type option doesn't work
> as documented).  With the documentation patch accepted, the bug
> can then be closed as resolved/fixed and taken off the easy hacks
> list.
>
>
> Martin


So here's my shot at fixing this in the documentation. Does that look okay?


gcc/ChangeLog:

  PR c/48116.

  * doc/invoke.texi (-Wreturn-type): Mention not warning on return with
   a void expression in a void function.
---
gcc/doc/invoke.texi | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

message, even when @option{-Wno-return-type} is specified.  The only
--
2.8.3

Comments

Martin Sebor June 2, 2016, 2:51 a.m. UTC | #1 
> So here's my shot at fixing this in the documentation. Does that look okay?
>

It looks good to me.  Just one minor point below.

> @@ -4055,8 +4055,12 @@ Warn whenever a function is defined with a
> return type that defaults
> to @code{int}.  Also warn about any @code{return} statement with no
> return value in a function whose return type is not @code{void}
> (falling off the end of the function body is considered returning
> -without a value), and about a @code{return} statement with an
> -expression in a function whose return type is @code{void}.
> +without a value).
> +
> +For a @code{return} statement with an expression in a function whose
> +return type is @code{void}, warn unless the expression type is also
> +@code{void}.  As a GNU extension, the latter case is accepted without a
> +warning unless @option{-Wpedantic} is used.

I would suggest to add that this only applies to C.  Otherwise
it's valid C++ so G++ accepts it without a pedantic warning.

As a disclaimer, someone else endowed with those special powers
will need to approve your final patch.  If you don't get a timely
approval please ping the patch weekly.

Martin
diff mbox

Patch

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index ce162a0..72e3f2d 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -4055,8 +4055,12 @@  Warn whenever a function is defined with a
return type that defaults
to @code{int}.  Also warn about any @code{return} statement with no
return value in a function whose return type is not @code{void}
(falling off the end of the function body is considered returning
-without a value), and about a @code{return} statement with an
-expression in a function whose return type is @code{void}.
+without a value).
+
+For a @code{return} statement with an expression in a function whose
+return type is @code{void}, warn unless the expression type is also
+@code{void}.  As a GNU extension, the latter case is accepted without a
+warning unless @option{-Wpedantic} is used.

For C++, a function without return type always produces a diagnostic