[Bug fortran/18540] New: Jumping into blocks gives error rather than warning

[Bug fortran/18540] New: Jumping into blocks gives error rather than warning

[paul dot richard dot thomas at cea dot fr]

program lau_error
!
! most compilers seem to permit this excremental bit of coding
! some give warnings that this is bad stuff
! gfortran barfs on it
!
! In file lau_error.f90:12
!
! 10    continue
!  1
! In file lau_error.f90:9
!
!    if ( i > 1 ) goto 10
!                       2
!Error: Label at (1) is not in the same block as the GOTO statement at (2)
!                                        Paul Thomas 18/11/04
!
  integer              ::    i , N = 2
  do i = 1 , N
    print * , 'i =  ', i
    if ( i > 1 ) goto 10                        !!jump into the if block *sigh*
    if ( i > 0 ) then
       print * , 'first statement in if block'
 10    continue
       print * , 'continue within if block'
    end if
    print * , 'out of if block'
  end do
  stop
end program lau_error

-- 
           Summary: Jumping into blocks gives error rather than warning
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: paul dot richard dot thomas at cea dot fr
                CC: gcc-bugs at gcc dot gnu dot org,paulthomas2 at wanadoo
                    dot fr


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-18 12:31 -------
Confirmed.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |diagnostic
   Last reconfirmed|0000-00-00 00:00:00         |2004-11-18 12:31:33
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[tobi at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
OtherBugsDependingO|                            |19292
              nThis|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[paulthomas2 at wanadoo dot fr]

------- Additional Comments From paulthomas2 at wanadoo dot fr  2005-01-06 18:17 -------
Subject: Re:  Jumping into blocks gives error rather than warning

Hi Tobias,

I just received a bunch of messages about gfortran bugs for which nothing 
has changed, as far as I can tell.  Is there a reason for this?  Am I 
supposed to affirm that they are still bugs?

Happy New Year to you all

Paul Thomas 




-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-01-06 18:19 -------
(In reply to comment #2)
> Subject: Re:  Jumping into blocks gives error rather than warning
> 
> Hi Tobias,
> 
> I just received a bunch of messages about gfortran bugs for which nothing 
> has changed, as far as I can tell.  Is there a reason for this?  Am I 
> supposed to affirm that they are still bugs?

No, Tobias just created a meta bug which records the failures in gfortran which worked in g77.

Thanks,
Andrew

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[fxcoudert at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fxcoudert at gcc dot gnu dot
                   |                            |org
   Last reconfirmed|2004-11-18 12:31:33         |2005-03-24 12:01:53
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.1.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[tobi at gcc dot gnu dot org]

------- Comment #22 from tobi at gcc dot gnu dot org  2006-01-26 10:14 -------
Fixed on trunk and 4.1.


-- 

tobi at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[tobi at gcc dot gnu dot org]

------- Comment #21 from tobi at gcc dot gnu dot org  2006-01-25 23:38 -------
Subject: Bug 18540

Author: tobi
Date: Wed Jan 25 23:38:34 2006
New Revision: 110232

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=110232
Log:
backport from r109914
fortran/
PR fortran/18540
* resolve.c (resolve_branch): Allow FORTRAN 66 cross-block GOTOs
as extension.

testsuite/
PR fortran/18540
* gfortran.dg/goto_1.f: New.

Added:
    branches/gcc-4_1-branch/gcc/testsuite/gfortran.dg/goto_1.f
      - copied unchanged from r110228, trunk/gcc/testsuite/gfortran.dg/goto_1.f
Modified:
    branches/gcc-4_1-branch/gcc/fortran/ChangeLog
    branches/gcc-4_1-branch/gcc/fortran/resolve.c
    branches/gcc-4_1-branch/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[tobi at gcc dot gnu dot org]

------- Comment #20 from tobi at gcc dot gnu dot org  2006-01-25 22:34 -------
Subject: Bug 18540

Author: tobi
Date: Wed Jan 25 22:34:17 2006
New Revision: 110228

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=110228
Log:
PR fortran/18540
* gfortran.dg/goto_1.f: New.

Added:
    trunk/gcc/testsuite/gfortran.dg/goto_1.f
Modified:
    trunk/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[tobi at gcc dot gnu dot org]

------- Comment #19 from tobi at gcc dot gnu dot org  2006-01-18 21:08 -------
Fixed on the mainline.  I will backport the cross-jumping part to 4.1.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[tobi at gcc dot gnu dot org]

------- Comment #18 from tobi at gcc dot gnu dot org  2006-01-18 20:54 -------
Subject: Bug 18540

Author: tobi
Date: Wed Jan 18 20:54:49 2006
New Revision: 109914

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=109914
Log:
PR fortran/18540
PR fortran/18937
* gfortran.h (BBT_HEADER): Move definition up.
(gfc_st_label): Add BBT_HEADER, remove 'prev' and 'next'.
* io.c (format_asterisk): Adapt initializer.
* resolve.c (resolve_branch): Allow FORTRAN 66 cross-block GOTOs
as extension.
* symbol.c (compare_st_labels): New function.
(gfc_free_st_label, free_st_labels, gfc_get_st_label): Convert to
using balanced binary tree.
* decl.c (match_char_length, gfc_match_old_kind_spec): Do away
with 'cnt'.
(warn_unused_label): Adapt to binary tree.
* match.c (gfc_match_small_literal_int): Only set cnt if non-NULL.
* primary.c (match_kind_param): Do away with cnt.

Also converted the ChangeLog to use latin1 characters.

Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/decl.c
    trunk/gcc/fortran/gfortran.h
    trunk/gcc/fortran/io.c
    trunk/gcc/fortran/match.c
    trunk/gcc/fortran/primary.c
    trunk/gcc/fortran/resolve.c
    trunk/gcc/fortran/symbol.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[tobi at gcc dot gnu dot org]

-- 

tobi at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |tobi at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2005-12-30 18:48:24         |2006-01-14 19:03:09
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[tobi at gcc dot gnu dot org]

------- Comment #17 from tobi at gcc dot gnu dot org  2006-01-09 18:56 -------
(In reply to comment #16)
> The idea of comment #14 and #15 looks better than mine, yes.

I'll continue what I've started, then.

> Which bug is the slowness bug btw?  We should really be discussing solutions
> for that bug in the audit trail of that bug instead of this one ;-)

PR18937.  I'll have it point to the discussion here.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[steven at gcc dot gnu dot org]

------- Comment #16 from steven at gcc dot gnu dot org  2006-01-09 18:35 -------
The idea of comment #14 and #15 looks better than mine, yes.

Which bug is the slowness bug btw?  We should really be discussing solutions
for that bug in the audit trail of that bug instead of this one ;-)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[tobi at gcc dot gnu dot org]

------- Comment #15 from tobi at gcc dot gnu dot org  2006-01-09 16:50 -------
Forgot to say: the validity check would then look like:

for (b = code->block: b != NULL; b = b->enclosing_block)
  if (b == label->block)
     /* valid GOTO */


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[tobi at gcc dot gnu dot org]

------- Comment #14 from tobi at gcc dot gnu dot org  2006-01-09 16:46 -------
Coming to think of it, I think that while your speedup would work, it would
probably be easier and even faster if we kept track of the enclosing blocks
while building the blocks and labels, so that the data structure would look
something like this:

gfc_st_label *label -> gfc_code *block -> gfc_code *enclosing_block ...

or maybe

gfc_st_label *label -> gfc_code *statement -> gfc_code *block
        -> gfc_code *enclosing_block ...

(where label is a statement label, statement the statement its attached to,
block the block containing the statement [this would e.g. be an if], etc.)

Then the time taken by the validation of the blocks would still scale linearly
with the number of blocks, but the length of the blocks would no longer play a
role, leaving us with linear behavior. 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[Tobias dot Schlueter at physik dot uni-muenchen dot de]

------- Comment #13 from Tobias dot Schlueter at physik dot uni-muenchen dot de  2006-01-08 22:53 -------
Subject: Re:  Jumping into blocks gives error rather than
 warning

steven at gcc dot gnu dot org wrote:
> ------- Comment #12 from steven at gcc dot gnu dot org  2006-01-08 22:23 -------
> Yes please.
> 
> And what do you think of the other idea to speed things up?

I know nothing about bitmaps :-)  I've just finished up coding a version which
puts them into a balanced binary tree, this should fix one quadratic
bottleneck.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[steven at gcc dot gnu dot org]

------- Comment #12 from steven at gcc dot gnu dot org  2006-01-08 22:23 -------
Yes please.

And what do you think of the other idea to speed things up?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[Tobias dot Schlueter at physik dot uni-muenchen dot de]

------- Comment #11 from Tobias dot Schlueter at physik dot uni-muenchen dot de  2006-01-08 22:16 -------
Subject: Re:  Jumping into blocks gives error rather than
 warning

steven at gcc dot gnu dot org wrote:
> ------- Comment #9 from steven at gcc dot gnu dot org  2006-01-08 21:45 -------
> Actually we already know for sure that the label exists and that it is a valid
> jump target.  From resolve_branch:

Indeed, I had missed that we already keep track of all existing labels when
parsing via the code in gfc_get_st_label.  I'll give your code a spin and
submit it, when it passes testing.  Ok?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[steven at gcc dot gnu dot org]

------- Comment #10 from steven at gcc dot gnu dot org  2006-01-08 21:54 -------
Note that this code in resolve_branch is only slow for deeply nested programs
with many gotos.  The code in resolve_branch is linear in the size of the
program, but if your program has many GOTO statements, say of the same order of
magnitude as the size of the program, then you effectively get quadratic
behavior in resolve_namespace.

I had the following idea to speed things up:
1. attach to each block a bitmap of statement labels defined in that block
2. compute a closure over the blocks tree to obtain a bitmap of all statement
   labels reachable from that block
3. in resolve_branch, only look at that bitmap.

You would only have to do 2. once for each program unit.  The bitmap check
would be cheap obviously.  You'd never have to walk the statements in
resolve_branch, so you would make the quadratic behavior go away. 
Unfortunately I've never found the time to try to implement this idea.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[steven at gcc dot gnu dot org]

------- Comment #9 from steven at gcc dot gnu dot org  2006-01-08 21:45 -------
Actually we already know for sure that the label exists and that it is a valid
jump target.  From resolve_branch:

  /* Step one: is this a valid branching target?  */

  if (lp->defined == ST_LABEL_UNKNOWN)
    {
      gfc_error ("Label %d referenced at %L is never defined", lp->value,
                 &lp->where);
      return;
    }

  if (lp->defined != ST_LABEL_TARGET)
    {
      gfc_error ("Statement at %L is not a valid branch target statement "
                 "for the branch statement at %L", &lp->where, &code->loc);
      return;
    }

  /* Step two: make sure this branch is not a branch to itself ;-)  */

  if (code->here == label)
    {
      gfc_warning ("Branch at %L causes an infinite loop", &code->loc);
      return;
    }

  /* Step three: Try to find the label in the parse tree. To do this,
     we traverse the tree block-by-block: first the block that
     contains this GOTO, then the block that it is nested in, etc.  We
     can ignore other blocks because branching into another block is
     not allowed.  */

Step three is what we can skip if we want to allow this kind of invalid jumping
around through a program unit.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[tobi at gcc dot gnu dot org]

------- Comment #8 from tobi at gcc dot gnu dot org  2006-01-08 21:42 -------
No, this is not sufficient, because you'll still need to find the label, unless
we have some gross code duplication that I'm not aware of.  What needs to be
done is adding a search through the entire program unit if no matching label is
found and GFC_STD_LEGACY is allowed.  Since this will take much longer than the
original parent block only search, we should really only do this, if need be. 
I think we also have a bug about slow code with lots of jumps, so it might
probably be worthwhile to overhaul this whole thing, to allow searching for
statement labels without having to traverse the gfc_code tree.


-- 

tobi at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[steven at gcc dot gnu dot org]

------- Comment #7 from steven at gcc dot gnu dot org  2006-01-08 21:33 -------
(From update of attachment 10595)
See comment #6


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #10595|0                           |1
        is obsolete|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[steven at gcc dot gnu dot org]

------- Comment #6 from steven at gcc dot gnu dot org  2006-01-08 21:32 -------
(From update of attachment 10595)
Index: resolve.c
===================================================================
--- resolve.c   (revision 109449)
+++ resolve.c   (working copy)
@@ -3579,9 +3579,12 @@ resolve_branch (gfc_st_label * label, gf

   if (found == NULL)
     {
-      /* still nothing, so illegal.  */
-      gfc_error_now ("Label at %L is not in the same block as the "
-                    "GOTO statement at %L", &lp->where, &code->loc);
+      /* Still nothing, so strictly illegal.  However, this kind of
+        what is now considered gross coding style was common in the
+        past.  So allow it for legacy code.  */
+      gfc_notify_std (GFC_STD_LEGACY,
+                     "Label at %L is not in the same block as the "
+                     "GOTO statement at %L", &lp->where, &code->loc);
       return;
     }


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[steven at gcc dot gnu dot org]

------- Comment #5 from steven at gcc dot gnu dot org  2006-01-08 21:30 -------
Created an attachment (id=10595)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=10595&action=view)
allow jumping into blocks in legacy mode

Something like this is probably all that's needed.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540

[Bug fortran/18540] Jumping into blocks gives error rather than warning

[pinskia at gcc dot gnu dot org]

------- Comment #4 from pinskia at gcc dot gnu dot org  2006-01-07 00:16 -------
*** Bug 25705 has been marked as a duplicate of this bug. ***


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |malitzke at metronets dot
                   |                            |com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18540