[Bug debug/29609] New: [regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[Bug debug/29609] New: [regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[debian-gcc at lists dot debian dot org]

[forwarded from http://bugs.debian.org/395057]

In the following sample code, gcc does not create enough 
debugging information to let gdb break in lines 27, 30, 33, 36. 

This makes debugging the main() function extremely painful. 
This is a regression from gcc 2.95 and gcc 3.3, both of which 
let gdb set a breakpoint on those lines. 

The ability to debug such code is very important to me, since 
I usually write my C functions with some cleanup code 
after a 'failure' label in the style below. 

[comment from Daniel Jacobowitz: Yes, this was a GDB bug earlier in the day. 
He's right.  I think it's jump threading, or something like that, running even
at -O0; seems like it shouldn't, for this reason.]


int f1(void)                    /* this "succeeds", i.e. returns 1 */ 
{ 
    return 1; 
} 

int f2(void)                    /* this "succeeds", i.e. returns 1 */ 
{ 
    return 1; 
} 

int f3(void)                    /* this "fails", i.e. returns 0 */ 
{ 
    return 0; 
} 

int f4(void)                    /* this "succeeds", i.e. returns 1 */ 
{ 
    return 1; 
} 


int main(int argc, char *argv[]) 
{ 
    int c; 

    if (!f1()) 
        goto failure; 

    if (!f2()) 
        goto failure; 

    if (!f3()) 
        goto failure; 

    if (!f4()) 
        goto failure; 

 success: 
    return 0; 

 failure: 
    return 1; 
}


-- 
           Summary: [regression] Even with  -O0 -g gcc optimizes a goto away
                    and I cannot debug
           Product: gcc
           Version: 3.1.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: debian-gcc at lists dot debian dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug debug/29609] [regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2006-10-26 22:05 -------
  [t.c : 26] if ([t.c : 26] D.1570 == 0) [t.c : 27] goto failure; else goto
<L0>;


This looks like an expand issue ...

Or a lower gimple issue.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug middle-end/29609] [4.1/4.2/4.3 Regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
          Component|debug                       |middle-end
     Ever Confirmed|0                           |1
           Keywords|                            |wrong-debug
      Known to fail|                            |4.3.0 4.2.0 4.0.4
      Known to work|                            |3.3.6
   Last reconfirmed|0000-00-00 00:00:00         |2007-03-14 18:58:43
               date|                            |
            Summary|[regression] Even with  -O0 |[4.1/4.2/4.3 Regression]
                   |-g gcc optimizes a goto away|Even with  -O0 -g gcc
                   |and I cannot debug          |optimizes a goto away and I
                   |                            |cannot debug
   Target Milestone|---                         |4.1.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug middle-end/29609] [4.1/4.2/4.3 Regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[mmitchel at gcc dot gnu dot org]

-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug middle-end/29609] [4.1/4.2/4.3 Regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[janis at gcc dot gnu dot org]

------- Comment #2 from janis at gcc dot gnu dot org  2007-04-25 21:31 -------
A regression hunt on powerpc-linux looking for DWARF2 line number information
for lines with gotos identified this patch:

    http://gcc.gnu.org/viewcvs?view=rev&rev=83385

    r83385 | hubicka | 2004-06-19 15:33:06 +0000 (Sat, 19 Jun 2004)


-- 

janis at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hubicka at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug middle-end/29609] [4.1/4.2/4.3 Regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[steven at gcc dot gnu dot org]

-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |steven at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2007-03-14 18:58:43         |2007-04-30 11:52:08
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug middle-end/29609] [4.1/4.2/4.3 Regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[steven at gcc dot gnu dot org]

------- Comment #3 from steven at gcc dot gnu dot org  2007-04-30 12:01 -------
There are at least 2 issues here:

1) We just lose the locus of the goto statements when we lower GIMPLE and when
we jump across forwarded blocks.

2) When we don't lose the locus in GIMPLE, we lose it in cfgexpand.

I'm working on a fix for both issues.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug middle-end/29609] [4.1/4.2/4.3 Regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[steven at gcc dot gnu dot org]

------- Comment #4 from steven at gcc dot gnu dot org  2007-05-11 21:51 -------
There doesn't seem to be another way to get this to work, than the proposed way
with extra basic blocks.  The things I've tried either break gcc, or gdb, or
debug info.  Unassigning.


-- 

steven at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug middle-end/29609] [4.1/4.2/4.3 Regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[steven at gcc dot gnu dot org]

------- Comment #5 from steven at gcc dot gnu dot org  2007-12-18 23:31 -------
xf. http://gcc.gnu.org/ml/gcc-patches/2007-04/msg01789.html

I was wrong to object to this patch -- there really doesn't seem to be any
other way.  It's funny, on the one hand we complain about the code quality of
-O0, but on the other we have to do quite silly things such as adding jumps to
jumps to keep rather important debug information around...

Olivier, any chance someone at AdaCore can pick this up and re-submit it to
gcc-patches?


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hainque at gcc dot gnu dot
                   |                            |org
             Status|NEW                         |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug middle-end/29609] [4.1/4.2/4.3 Regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[hainque at adacore dot com]

------- Comment #6 from hainque at adacore dot com  2007-12-19 08:30 -------
Subject: Re:  [4.1/4.2/4.3 Regression] Even with  -O0 -g gcc optimizes a goto
away and I cannot debug

Hi Steven,

steven at gcc dot gnu dot org wrote:
> xf. http://gcc.gnu.org/ml/gcc-patches/2007-04/msg01789.html
> 
> I was wrong to object to this patch

 No problem, and many thanks for getting back to us on this issue.

 What really matters is feedback/discussion IMO, and your comments had
 us look for better ways to perform the task. This is a positive outcome
 even if we haven't (yet) pushed further for an inclusion into the FSF
 tree.

> there really doesn't seem to be any other way.  It's funny, on the
> one hand we complain about the code quality of -O0, but on the other
> we have to do quite silly things such as adding jumps to jumps to
> keep rather important debug information around...

 Right. We have several constraints at play (want to debug, want the
 ability to debug (-g) not to modify the generated code, and want to
 limit generated code bloats), and it's not always possible to progress
 on one aspect without effects on the others.

 I like the recently suggested "-Og" idea because it offers a way through.

> Olivier, any chance someone at AdaCore can pick this up and re-submit it to
> gcc-patches?

 We can definitely resubmit the current version we have (I copied the
 author). Thanks again for your feedback,

 Olivier




-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug middle-end/29609] [4.1/4.2/4.3 Regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[hainque at adacore dot com]

------- Comment #7 from hainque at adacore dot com  2007-12-19 10:06 -------
Subject: Re:  [4.1/4.2/4.3 Regression] Even with  -O0 -g gcc optimizes a goto
away and I cannot debug

Olivier Hainque wrote:
>  We can definitely resubmit the current version we have (I copied the
>  author). Thanks again for your feedback,

 Actually, there was another related submission at

   http://gcc.gnu.org/ml/gcc-patches/2007-09/msg00099.html

 There was an interesting exchange with Richard Guenther there, which
 didn't quite reach a conclusion at the time.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug middle-end/29609] [4.1/4.2/4.3 Regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[steven at gcc dot gnu dot org]

-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
   Last reconfirmed|2007-04-30 11:52:08         |2008-01-07 17:40:51
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug middle-end/29609] [4.2/4.3/4.4 Regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[jsm28 at gcc dot gnu dot org]

------- Comment #8 from jsm28 at gcc dot gnu dot org  2008-07-04 21:43 -------
Closing 4.1 branch.


-- 

jsm28 at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.1/4.2/4.3/4.4 Regression]|[4.2/4.3/4.4 Regression]
                   |Even with  -O0 -g gcc       |Even with  -O0 -g gcc
                   |optimizes a goto away and I |optimizes a goto away and I
                   |cannot debug                |cannot debug
   Target Milestone|4.1.3                       |4.2.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug middle-end/29609] [4.2/4.3/4.4 Regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[jakub at gcc dot gnu dot org]

-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |jakub at gcc dot gnu dot org
                   |dot org                     |
                URL|                            |http://gcc.gnu.org/ml/gcc-
                   |                            |patches/2008-
                   |                            |10/msg00017.html
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2008-01-07 17:40:51         |2008-10-03 08:54:37
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug middle-end/29609] [4.2/4.3/4.4 Regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[jakub at gcc dot gnu dot org]

------- Comment #9 from jakub at gcc dot gnu dot org  2008-10-07 18:50 -------
Subject: Bug 29609

Author: jakub
Date: Tue Oct  7 18:48:40 2008
New Revision: 140948

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=140948
Log:
        PR debug/29609
        PR debug/36690
        PR debug/37616
        * basic-block.h (struct edge_def): Add goto_block field.
        * cfglayout.c (fixup_reorder_chain): Ensure that there is at least
        one insn with locus corresponding to edge's goto_locus if !optimize.
        * profile.c (branch_prob): Copy edge's goto_block.
        * cfgrtl.c (force_nonfallthru_and_redirect): Use goto_locus for
        emitted jumps.
        (cfg_layout_merge_blocks): Emit a nop with edge's goto_locus
        locator in between the merged basic blocks if !optimize and needed.
        * cfgexpand.c (expand_gimple_cond): Convert goto_block and
        goto_locus into RTL locator.  For unconditional jump use that
        locator for the jump insn.
        (expand_gimple_cond): Convert goto_block and goto_locus into
        RTL locator for all remaining edges.  For unconditional jump
        use that locator for the jump insn.
        * cfgcleanup.c (try_forward_edges): Avoid the optimization if
        there is more than one edge or insn locator along the forwarding
        edges and !optimize.  If there is just one, set e->goto_locus.
        * tree-cfg.c (make_cond_expr_edges, make_goto_expr_edges): Set also
        edge's goto_block.
        (move_block_to_fn): Adjust edge's goto_block.

        * gcc.dg/debug/pr29609-1.c: New test.
        * gcc.dg/debug/pr29609-2.c: New test.
        * gcc.dg/debug/pr36690-1.c: New test.
        * gcc.dg/debug/pr36690-2.c: New test.
        * gcc.dg/debug/pr36690-3.c: New test.
        * gcc.dg/debug/pr37616.c: New test.
        * gcc.dg/debug/dwarf2/pr29609-1.c: New test.
        * gcc.dg/debug/dwarf2/pr29609-2.c: New test.
        * gcc.dg/debug/dwarf2/pr36690-1.c: New test.
        * gcc.dg/debug/dwarf2/pr36690-2.c: New test.
        * gcc.dg/debug/dwarf2/pr36690-3.c: New test.
        * gcc.dg/debug/dwarf2/pr37616.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/debug/dwarf2/pr29609-1.c
    trunk/gcc/testsuite/gcc.dg/debug/dwarf2/pr29609-2.c
    trunk/gcc/testsuite/gcc.dg/debug/dwarf2/pr36690-1.c
    trunk/gcc/testsuite/gcc.dg/debug/dwarf2/pr36690-2.c
    trunk/gcc/testsuite/gcc.dg/debug/dwarf2/pr36690-3.c
    trunk/gcc/testsuite/gcc.dg/debug/dwarf2/pr37616.c
    trunk/gcc/testsuite/gcc.dg/debug/pr29609-1.c
    trunk/gcc/testsuite/gcc.dg/debug/pr29609-2.c
    trunk/gcc/testsuite/gcc.dg/debug/pr36690-1.c
    trunk/gcc/testsuite/gcc.dg/debug/pr36690-2.c
    trunk/gcc/testsuite/gcc.dg/debug/pr36690-3.c
    trunk/gcc/testsuite/gcc.dg/debug/pr37616.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/basic-block.h
    trunk/gcc/cfgcleanup.c
    trunk/gcc/cfgexpand.c
    trunk/gcc/cfglayout.c
    trunk/gcc/cfgrtl.c
    trunk/gcc/profile.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-cfg.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug middle-end/29609] [4.2/4.3/4.4 Regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[jakub at gcc dot gnu dot org]

------- Comment #10 from jakub at gcc dot gnu dot org  2008-10-07 19:01 -------
Fixed.


-- 

jakub at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609

[Bug middle-end/29609] [4.2/4.3/4.4 Regression] Even with -O0 -g gcc optimizes a goto away and I cannot debug

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.2.5                       |4.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29609