[Bug c/107942] New: [10/11/12/13 Regression] Documentation of the volatile style for noreturn is gone

[Bug c/107942] New: [10/11/12/13 Regression] Documentation of the volatile style for noreturn is gone

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107942

            Bug ID: 107942
           Summary: [10/11/12/13 Regression] Documentation of the volatile
                    style for noreturn is gone
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: documentation
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

r5-7698-g8648c55f3b703a removed the documentation of the volatile style of
noreturn even though it is still implemented as of today.
Take:
```
typedef void voidfn ();

volatile voidfn fatal;

void fatal() {}
```

This still warns today with the C front-end:
<source>: In function 'fatal':
<source>:8:1: warning: 'noreturn' function does return
    8 | }
      | ^

The reasoning why the documentation was removed was it references an (real) old
version of GCC.

[Bug c/107942] [10/11/12/13 Regression] Documentation of the volatile style for noreturn is gone

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107942

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |4.8.5
      Known to fail|                            |5.1.0
   Target Milestone|---                         |10.5

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
https://gcc.gnu.org/onlinedocs/gcc-4.8.5/gcc/Function-Attributes.html#index-g_t_0040code_007bnoreturn_007d-function-attribute-2696

[Bug c/107942] [10/11/12/13 Regression] Documentation of the volatile style for noreturn is gone and const style for const attribute is gone

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107942

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[10/11/12/13 Regression]    |[10/11/12/13 Regression]
                   |Documentation of the        |Documentation of the
                   |volatile style for noreturn |volatile style for noreturn
                   |is gone                     |is gone and const style for
                   |                            |const attribute is gone

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Const is gone the same way with the same patch.

[Bug c/107942] [10/11/12/13 Regression] Documentation of the volatile style for noreturn is gone and const style for const attribute is gone

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107942

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Here is the sample program to prove that const is still handled like const
attribute:
```
typedef int voidfn (void);

const voidfn constt;
[[gnu::noipa]]
int constt(void) {return 1;}

int f(void)
{
    return constt()+constt();
}
```

[Bug c/107942] [10/11/12/13 Regression] Documentation of the volatile style for noreturn is gone and const style for const attribute is gone

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107942

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Reference to the patch that was sent:
https://gcc.gnu.org/pipermail/gcc-patches/2015-March/414153.html

[Bug c/107942] [10/11/12/13 Regression] Documentation of the volatile style for noreturn is gone and const style for const attribute is gone

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107942

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Oh it is still part of the keyword index too:
https://gcc.gnu.org/onlinedocs/gcc/Keyword-Index.html#Keyword-Index

Which links to:
https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#index-volatile-applied-to-function

[Bug c/107942] [10/11/12/13 Regression] Documentation of the volatile style for noreturn is gone and const style for const attribute is gone

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107942

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #5)
> Oh it is still part of the keyword index too:
> https://gcc.gnu.org/onlinedocs/gcc/Keyword-Index.html#Keyword-Index
> 
> Which links to:
> https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#index-volatile-
> applied-to-function

Likewise for const:
https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#index-const-applied-to-function

[Bug c/107942] [10/11/12/13 Regression] Documentation of the volatile style for noreturn is gone and const style for const attribute is gone

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107942

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jsm28 at gcc dot gnu.org
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2022-12-21

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
I wonder if we should remove this handling?  (I think it's good the manual no
longer suggests it)

I suppose the standard doesn't give const or volatile qualification any
semantics (or requires a diagnostic)

[Bug c/107942] [11/12/13/14 Regression] Documentation of the volatile style for noreturn is gone and const style for const attribute is gone

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107942

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.5                        |11.5

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 10 branch is being closed.

[Bug c/107942] [11/12/13/14 Regression] Documentation of the volatile style for noreturn is gone and const style for const attribute is gone

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107942

--- Comment #9 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Sandra Loosemore <sandra@gcc.gnu.org>:

https://gcc.gnu.org/g:dbda6cd58308bf13bf9b367604cb459b1c627344

commit r14-8258-gdbda6cd58308bf13bf9b367604cb459b1c627344
Author: Sandra Loosemore <sandra@codesourcery.com>
Date:   Thu Jan 18 18:28:22 2024 +0000

    Restore documentation for const/volatile functions [PR107942]

    In r5-7698-g8648c55f3b703a I accidentally removed the documentation of
    GCC's special interpretation of const/volatile qualifiers on functions
    from the function attributes section, thinking this was just a
    bit-rotten leftover from old versions of GCC.  PR107942 points out
    that this functionality is still present even though the docs are now gone.

    I decided this material didn't really belong in the function
    attributes discussion, but a new subsection in the general list of GCC
    extensions to the C language.  And I agree with the comment in the
    issue that we shouldn't really recommend this usage any more.

    gcc/ChangeLog
            PR c/107942
            * doc/extend.texi (C Extensions): Add new section to menu.
            (Function Attributes):  Move dangling index entries to....
            (Const and Volatile Functions): New section.

[Bug c/107942] [11/12/13/14 Regression] Documentation of the volatile style for noreturn is gone and const style for const attribute is gone

[sandra at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107942

sandra at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #10 from sandra at gcc dot gnu.org ---
Fixed.