[Bug c/14411] New: Request for setjmp/longjmp attributes

[Bug c/14411] New: Request for setjmp/longjmp attributes

[avn at any dot ru]

While working on a project that uses a function with setjmp-like semantics, it 
became necessary to supply the optimizer with such information. Otherwise, the 
following code: 
 
void *ptr = NULL; 
if (mysetjmp()) { 
	if (ptr) free(ptr); 
} 
else { 
	/* ... */ 
	ptr = malloc(...); 
	/* ... */ 
} 
 
does not do the call to free() when compiled with -O2 (the optimizer believes 
the ptr still is NULL and eliminates the call to free() completely).

-- 
           Summary: Request for setjmp/longjmp attributes
           Product: gcc
           Version: 3.3.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: avn at any dot ru
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14411

[Bug c/14411] Request for setjmp/longjmp attributes

[avn at any dot ru]

------- Additional Comments From avn at any dot ru  2004-03-03 17:24 -------
Created an attachment (id=5855)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=5855&action=view)
Patch to resolve this

Attached the patch to allow specification of 'setjmp'/'longjmp' attributes to a
function.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14411

[Bug c/14411] Request for setjmp/longjmp attributes

[avn at any dot ru]

------- Additional Comments From avn at any dot ru  2004-03-03 17:25 -------
With the patch applied (against 3.3.3 sources), the example code is compiled 
correctly if mysetjmp() is declared with __attribute__((setjmp)). 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14411

[Bug c/14411] Request for setjmp/longjmp attributes

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-03-03 17:32 -------
Confirmed, patches goto gcc-patches@gcc.gnu.org with a changelog and a description.  Please read 
<http://gcc.gnu.org/contribute.html> ____before____ sumbitting them though.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-03-03 17:32:10
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14411

[Bug c/14411] Request for setjmp/longjmp attributes

[jsm at polyomino dot org dot uk]

------- Additional Comments From jsm at polyomino dot org dot uk  2004-03-03 17:46 -------
Subject: Re:  New: Request for setjmp/longjmp attributes

On Wed, 3 Mar 2004, avn at any dot ru wrote:

> While working on a project that uses a function with setjmp-like semantics, it 
> became necessary to supply the optimizer with such information. Otherwise, the 
> following code: 

Might such an attribute for setjmp be specifiable in a way making it
suitable for vfork as well?  special_function_p presently handles both the
same.  However, we want to get rid of this ad hoc handling and replace it
with proper attributes.  For ISO C functions these should be handled
through built-in functions in builtins.def.  (There may be a complication
because __builtin_setjmp does not correspond to the ISO C setjmp function,
and likewith __builtin_longjmp, so this cleanup should probably be
separated from the base patch that adds the attributes with testcases and
documentation.)  For non-ISO functions not in the reserved namespaces,
these should be handled through fixincludes: the correct attributes are
needed for correct compilation, so it isn't OK for them to be disabled in
ISO C mode.  (Since these functions involve types defined in headers, we
don't need to allow for users declaring them without including the
appropriate headers.)



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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14411

[Bug c/14411] Request for setjmp/longjmp attributes

[schwab at suse dot de]

------- Additional Comments From schwab at suse dot de  2004-03-03 20:13 -------
Even with setjmp you must declare such a variable as volatile to get correct 
behaviour. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14411

[Bug c/14411] Request for setjmp/longjmp attributes

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-06-02 03:49 -------
What we need is an attribute that says may return twice.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
   Last reconfirmed|2004-03-03 17:32:10         |2004-06-02 03:49:16
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14411

[Bug c/14411] Request for setjmp/longjmp attributes

[avn at any dot ru]

------- Additional Comments From avn at any dot ru  2004-06-02 06:41 -------
Should I update the patch, renaming this attribute to somewhat like 
"__attribute__((double_return))"? And what should 'longjmp' be renamed to, then? 

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14411

[Bug c/14411] Request for setjmp/longjmp attributes

[zack at gcc dot gnu dot org]

------- Additional Comments From zack at gcc dot gnu dot org  2004-11-30 07:47 -------
+kw, milestone; assigning to myself for commitment once 4.1 opens.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |zack at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED
           Keywords|                            |patch
   Target Milestone|---                         |4.1.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14411

[Bug c/14411] Request for setjmp/longjmp attributes

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2005-03-08 13:19 -------
Subject: Bug 14411

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	rth@gcc.gnu.org	2005-03-08 13:19:41

Modified files:
	gcc            : ChangeLog c-common.c calls.c tree.h 
	gcc/doc        : extend.texi 
Added files:
	gcc/testsuite/gcc.dg: attr-returns_twice-1.c 

Log message:
	PR c/14411
	* calls.c (flags_from_decl_or_type): Handle eturns_twice' attribute.
	* c-common.c (handle_returns_twice): New function.
	(c_common_attribute_table): Declare eturns_twice' attribute.
	* doc/extend.texi: Document eturns_twice' attribute.
	* tree.h (DECL_IS_RETURNS_TWICE): New macro.
	(struct tree_decl): Add returns_twice_flag.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.7728&r2=2.7729
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/c-common.c.diff?cvsroot=gcc&r1=1.606&r2=1.607
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/calls.c.diff?cvsroot=gcc&r1=1.380&r2=1.381
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/tree.h.diff?cvsroot=gcc&r1=1.698&r2=1.699
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/doc/extend.texi.diff?cvsroot=gcc&r1=1.242&r2=1.243
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gcc.dg/attr-returns_twice-1.c.diff?cvsroot=gcc&r1=NONE&r2=1.1



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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14411

[Bug c/14411] Request for setjmp/longjmp attributes

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-03-08 14:36 -------
Fixed.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14411

[Bug c/14411] Request for setjmp/longjmp attributes

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-03-08 14:38 -------
Actually I take that back, it is only 1 out of 3 which was applied.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14411

[Bug c/14411] Request for setjmp/longjmp attributes

[avn at any dot ru]

------- Additional Comments From avn at any dot ru  2005-03-08 19:02 -------
Actually, it is fixed. The other two patches that I pinged are not related to 
this PR. 

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14411