[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[d.g.gorbachev at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026

--- Comment #19 from Dmitry Gorbachev <d.g.gorbachev at gmail dot com> 2011-03-01 06:41:57 UTC ---
GCC documentation has been changed. __attribute__((unused)) on labels can be
used in C++ code since GCC version 4.5.0. This PR should be closed probably.

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |manu at gcc dot gnu.org
         Resolution|                            |FIXED

--- Comment #20 from Manuel López-Ibáñez <manu at gcc dot gnu.org> 2011-03-01 08:51:32 UTC ---
(In reply to comment #19)
> GCC documentation has been changed. __attribute__((unused)) on labels can be
> used in C++ code since GCC version 4.5.0. This PR should be closed probably.

The less, the merrier. Thanks!

(If you get a gcc.gnu.org account, you can do bug management:
http://gcc.gnu.org/svnwrite.html#authenticated)

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.5.0

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-02-24 19:09 -------
I think it would be sensible if it would. But I checked this morning, 
and it doesn't. 
 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[giovannibajo at libero dot it]

------- Additional Comments From giovannibajo at libero dot it  2004-02-24 18:46 -------
Isn't this supposed to work:

mylabel __attribute__((unused)): 

Does it work? Maybe it should.

-- 
           What    |Removed                     |Added
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                 CC|                            |giovannibajo at libero dot
                   |                            |it


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-02-24 14:52 -------
There indeed doesn't seem to be a way. 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[msp at nortelnetworks dot com]

------- Additional Comments From msp at nortelnetworks dot com  2004-02-24 14:35 -------
Subject: Re:  __attribute__ ((unused) seems misdocumented

Does that mean that there is no alternative way of tell gcc, in c++ mode,
that the label might not be used?

If so, I will raise a bug/enhancement request against bison suggesting
they change their usage to be #ifndef __cplusplus or something.

Cheers
Mark



On Tue, 24 Feb 2004, bangerth at dealii dot org wrote:

>
> ------- Additional Comments From bangerth at dealii dot org  2004-02-24 14:21 -------
> The reason why it is not allowed in C++ on labels has been stated
> several times: in C++, a variable declaration can follow a label,
> so the attribute that you want to attach to the label really goes
> to the next statement; gcc expects it to be a declaration, and
> complains if it can't find one.
>
> W.
>
>



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-02-24 14:21 -------
The reason why it is not allowed in C++ on labels has been stated 
several times: in C++, a variable declaration can follow a label, 
so the attribute that you want to attach to the label really goes 
to the next statement; gcc expects it to be a declaration, and 
complains if it can't find one. 
 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[msp at nortelnetworks dot com]

------- Additional Comments From msp at nortelnetworks dot com  2004-02-24 13:41 -------
(In reply to comment #12)
> (In reply to comment #11)

Sorry, my example got mangled when I copied it in....

void fred()
{
   int x;
   
yyerrlab1:
 __attribute__ ((__unused__))

 x = 42;
 
}


-- 
           What    |Removed                     |Added
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                 CC|                            |msp at nortelnetworks dot
                   |                            |com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[msp at nortelnetworks dot com]

------- Additional Comments From msp at nortelnetworks dot com  2004-02-24 13:37 -------
(In reply to comment #11)
> Actually now with 3.4.0 the part about C++ is wrong because now you can use
the attribute in 
> C++.  The problem is that the attribute can be put on variables also not just
functions.

Actually for C the attribute can also be applied to labels! BUT not for C++.

The following code (based on the default output from bison 1.875), will compile
in C mode, but not in C++ mode:-

void fred()
{
   int x;
   
yyerrlab1:
 __attribute__ ((__unused__))

1 x = 42;
 
}

The intention is to tell the compiler that yyerrlab1: may be unused, but in C++
mode you get the following error:-

p.cc: In function `void fred()':
p.cc:8: error: ISO C++ forbids declaration of `x' with no type
p.cc:8: error: redeclaration of `int x'
p.cc:3: error: `int x' previously declared here
p.cc:8: error: declaration of `int x'
p.cc:3: error: conflicts with previous declaration `int x'

It also allows its use And even more cunningly it can (or should be) possible to
attach it to labels.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-01-31 20:29 -------
Actually now with 3.4.0 the part about C++ is wrong because now you can use the attribute in 
C++.  The problem is that the attribute can be put on variables also not just functions.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[bh at techhouse dot brown dot edu]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026



------- Additional Comments From bh at techhouse dot brown dot edu  2003-11-05 14:28 -------
Given that, how is the following wording:

    @cindex @code{unused} attribute.
    @item unused
    This attribute suppresses the warning about a variable or function that is
    not being used anywhere in its scope.

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[pinskia at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026


pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2003-07-18 23:30:56         |2003-11-05 07:20:44
               date|                            |


------- Additional Comments From pinskia at gcc dot gnu dot org  2003-11-05 07:20 -------
I think the last sentence means that c++ supports that definition of agruments can be 
unamed, other than that the unused is not misdocumented.

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[neroden at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026



------- Additional Comments From neroden at gcc dot gnu dot org  2003-08-03 15:47 -------
The last sentence is supposed to mean "attribute unused is not supported by
G++", plus some bogus rationale.  Which is false anyway, I think.

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[pinskia at physics dot uc dot edu]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026


pinskia at physics dot uc dot edu changed:

           What    |Removed                     |Added
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         AssignedTo|bje at gcc dot gnu dot org  |unassigned at gcc dot gnu
                   |                            |dot org
             Status|ASSIGNED                    |NEW


------- Additional Comments From pinskia at physics dot uc dot edu  2003-08-03 15:42 -------
Reassign this one to no one.

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[bje at wasabisystems dot com]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026



------- Additional Comments From bje at wasabisystems dot com  2003-07-20 23:57 -------
Subject: Re:  __attribute__ ((unused) seems misdocumented

"dhazeghi at yahoo dot com" <gcc-bugzilla@gcc.gnu.org> writes:

> Ben, this has been assigned to you for a few months, any progress?

I guess I picked it off the stack to work on it, but never got
started.  Feel free to reassign it to anyone interested.

Ben

[Bug c++/5026] __attribute__ ((unused) seems misdocumented

[dhazeghi at yahoo dot com]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5026


dhazeghi at yahoo dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |documentation
   Last reconfirmed|0000-00-00 00:00:00         |2003-07-18 23:30:56
               date|                            |


------- Additional Comments From dhazeghi at yahoo dot com  2003-07-18 23:30 -------
Ben, this has been assigned to you for a few months, any progress?