* [Bug c/95141] [8/9/10/11 Regression] Incorrect integer overflow warning message for bitand expression
2020-05-14 19:51 [Bug c/95141] New: Incorrect integer overflow warning message for bitand expression yadongh at vt dot edu
@ 2020-05-15 7:30 ` jakub at gcc dot gnu.org
2020-05-15 9:02 ` rguenth at gcc dot gnu.org
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From: jakub at gcc dot gnu.org @ 2020-05-15 7:30 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95141
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
Last reconfirmed| |2020-05-15
Target Milestone|--- |8.5
Ever confirmed|0 |1
Summary|Incorrect integer overflow |[8/9/10/11 Regression]
|warning message for bitand |Incorrect integer overflow
|expression |warning message for bitand
| |expression
Status|UNCONFIRMED |NEW
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Started with r7-7544-g2d143ba8cfef7ef480c639882fd5518b7afd822b
^ permalink raw reply [flat|nested] 11+ messages in thread* [Bug c/95141] [8/9/10/11 Regression] Incorrect integer overflow warning message for bitand expression
2020-05-14 19:51 [Bug c/95141] New: Incorrect integer overflow warning message for bitand expression yadongh at vt dot edu
2020-05-15 7:30 ` [Bug c/95141] [8/9/10/11 Regression] " jakub at gcc dot gnu.org
@ 2020-05-15 9:02 ` rguenth at gcc dot gnu.org
2020-05-18 13:28 ` rguenth at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2020-05-15 9:02 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95141
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot gnu.org
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
So there's already (OVF) at
((long unsigned int) IA1 & 158(OVF)) & 1
but we only check
375 if (TREE_OVERFLOW_P (ret)
376 && !TREE_OVERFLOW_P (op0)
377 && !TREE_OVERFLOW_P (op1))
378 overflow_warning (EXPR_LOC_OR_LOC (expr, input_location), ret,
expr);
which doesn't catch the pre-existing overflow on op0 which then propagates.
The original overflow is introduced folding short 158 to signed char -98(OVF)
via convert.c:do_narrow:
437 /* We should do away with all this once we have a proper
438 type promotion/demotion pass, see PR45397. */
439 expr = maybe_fold_build2_loc (dofold, loc, ex_form, typex,
440 convert (typex, arg0),
441 convert (typex, arg1));
specifically the convert (typex, arg1).
Now TREE_OVERFLOW in general is quite a fragile thing, but it's tempting to
adjust the overflow_warning guard for this case ...
The do_narrow code also specifically looks for overflow cases that matter
and does not perform narrowing then so clearing TREE_OVERFLOW there would
also look reasonable.
Thus like the following? Should be cheaper than adding walk_tree to the
diagnostic guard.
diff --git a/gcc/convert.c b/gcc/convert.c
index 42509c518a9..ed00ded1a89 100644
--- a/gcc/convert.c
+++ b/gcc/convert.c
@@ -436,9 +436,16 @@ do_narrow (location_t loc,
}
/* We should do away with all this once we have a proper
type promotion/demotion pass, see PR45397. */
+ /* Above we checked for all cases where overflow matters, avoid
+ geneating overflowed constants here which otherwise propagate
+ and cause spurious warnings, see PR95141. */
+ tree converted_arg1 = convert (typex, arg1);
+ if (TREE_OVERFLOW_P (converted_arg1)
+ && !TREE_OVERFLOW_P (arg1))
+ converted_arg1 = drop_tree_overflow (converted_arg1);
expr = maybe_fold_build2_loc (dofold, loc, ex_form, typex,
convert (typex, arg0),
- convert (typex, arg1));
+ converted_arg1);
return convert (type, expr);
}
^ permalink raw reply [flat|nested] 11+ messages in thread* [Bug c/95141] [8/9/10/11 Regression] Incorrect integer overflow warning message for bitand expression
2020-05-14 19:51 [Bug c/95141] New: Incorrect integer overflow warning message for bitand expression yadongh at vt dot edu
2020-05-15 7:30 ` [Bug c/95141] [8/9/10/11 Regression] " jakub at gcc dot gnu.org
2020-05-15 9:02 ` rguenth at gcc dot gnu.org
@ 2020-05-18 13:28 ` rguenth at gcc dot gnu.org
2020-05-20 7:40 ` cvs-commit at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2020-05-18 13:28 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95141
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #2)
> So there's already (OVF) at
>
> ((long unsigned int) IA1 & 158(OVF)) & 1
>
> but we only check
>
> 375 if (TREE_OVERFLOW_P (ret)
> 376 && !TREE_OVERFLOW_P (op0)
> 377 && !TREE_OVERFLOW_P (op1))
> 378 overflow_warning (EXPR_LOC_OR_LOC (expr, input_location),
> ret, expr);
>
> which doesn't catch the pre-existing overflow on op0 which then propagates.
>
> The original overflow is introduced folding short 158 to signed char -98(OVF)
> via convert.c:do_narrow:
>
> 437 /* We should do away with all this once we have a proper
> 438 type promotion/demotion pass, see PR45397. */
> 439 expr = maybe_fold_build2_loc (dofold, loc, ex_form, typex,
> 440 convert (typex, arg0),
> 441 convert (typex, arg1));
>
> specifically the convert (typex, arg1).
>
> Now TREE_OVERFLOW in general is quite a fragile thing, but it's tempting to
> adjust the overflow_warning guard for this case ...
>
> The do_narrow code also specifically looks for overflow cases that matter
> and does not perform narrowing then so clearing TREE_OVERFLOW there would
> also look reasonable.
>
> Thus like the following? Should be cheaper than adding walk_tree to the
> diagnostic guard.
>
> diff --git a/gcc/convert.c b/gcc/convert.c
> index 42509c518a9..ed00ded1a89 100644
> --- a/gcc/convert.c
> +++ b/gcc/convert.c
> @@ -436,9 +436,16 @@ do_narrow (location_t loc,
> }
> /* We should do away with all this once we have a proper
> type promotion/demotion pass, see PR45397. */
> + /* Above we checked for all cases where overflow matters, avoid
> + geneating overflowed constants here which otherwise propagate
> + and cause spurious warnings, see PR95141. */
> + tree converted_arg1 = convert (typex, arg1);
> + if (TREE_OVERFLOW_P (converted_arg1)
> + && !TREE_OVERFLOW_P (arg1))
> + converted_arg1 = drop_tree_overflow (converted_arg1);
> expr = maybe_fold_build2_loc (dofold, loc, ex_form, typex,
> convert (typex, arg0),
> - convert (typex, arg1));
> + converted_arg1);
> return convert (type, expr);
> }
Regresses
FAIL: gcc.dg/overflow-warn-5.c (test for warnings, line 6)
which looks like a useful warning to preserve. Lame "walk-tree" variant
catching this case:
diff --git a/gcc/c/c-fold.c b/gcc/c/c-fold.c
index 63becfeaf2c..bd21d247051 100644
--- a/gcc/c/c-fold.c
+++ b/gcc/c/c-fold.c
@@ -374,6 +374,7 @@ c_fully_fold_internal (tree expr, bool in_init, bool
*maybe_const_operands,
ret = fold (expr);
if (TREE_OVERFLOW_P (ret)
&& !TREE_OVERFLOW_P (op0)
+ && !(BINARY_CLASS_P (op0) && TREE_OVERFLOW_P (TREE_OPERAND (op0, 1)))
&& !TREE_OVERFLOW_P (op1))
overflow_warning (EXPR_LOC_OR_LOC (expr, input_location), ret, expr);
if (code == LSHIFT_EXPR
^ permalink raw reply [flat|nested] 11+ messages in thread* [Bug c/95141] [8/9/10/11 Regression] Incorrect integer overflow warning message for bitand expression
2020-05-14 19:51 [Bug c/95141] New: Incorrect integer overflow warning message for bitand expression yadongh at vt dot edu
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2020-05-18 13:28 ` rguenth at gcc dot gnu.org
@ 2020-05-20 7:40 ` cvs-commit at gcc dot gnu.org
2020-05-20 7:42 ` [Bug c/95141] [8/9/10 " rguenth at gcc dot gnu.org
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From: cvs-commit at gcc dot gnu.org @ 2020-05-20 7:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95141
--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:
https://gcc.gnu.org/g:4a88caf21a0a85129f6c985ca13ba3eb54ff5366
commit r11-509-g4a88caf21a0a85129f6c985ca13ba3eb54ff5366
Author: Richard Biener <rguenther@suse.de>
Date: Tue May 19 07:58:33 2020 +0200
c/95141 - fix bogus integer overflow warning
This fixes an integer overflow warning that ultimatively happens because
of TREE_OVERFLOW propagating through transforms and the existing guard
against this,
375 if (TREE_OVERFLOW_P (ret)
376 && !TREE_OVERFLOW_P (op0)
377 && !TREE_OVERFLOW_P (op1))
378 overflow_warning (EXPR_LOC_OR_LOC (expr, input_location,
being insufficient. Rather than trying to use sth like walk_tree to
exhaustively walk operands (with the possibility of introducing
quadraticness when folding larger expressions recursively) the
following amends the above with an ad-hoc test for a binary op0
with a possibly constant op1.
2020-05-30 Richard Biener <rguenther@suse.de>
PR c/95141
gcc/c
* c-fold.c (c_fully_fold_internal): Enhance guard on
overflow_warning.
gcc/testsuite
* gcc.dg/pr95141.c: New testcase.
^ permalink raw reply [flat|nested] 11+ messages in thread* [Bug c/95141] [8/9/10 Regression] Incorrect integer overflow warning message for bitand expression
2020-05-14 19:51 [Bug c/95141] New: Incorrect integer overflow warning message for bitand expression yadongh at vt dot edu
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2020-05-20 7:40 ` cvs-commit at gcc dot gnu.org
@ 2020-05-20 7:42 ` rguenth at gcc dot gnu.org
2020-06-23 11:06 ` cvs-commit at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2020-05-20 7:42 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95141
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Known to fail| |10.1.0
Summary|[8/9/10/11 Regression] |[8/9/10 Regression]
|Incorrect integer overflow |Incorrect integer overflow
|warning message for bitand |warning message for bitand
|expression |expression
Known to work| |11.0
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed on trunk sofar.
^ permalink raw reply [flat|nested] 11+ messages in thread* [Bug c/95141] [8/9/10 Regression] Incorrect integer overflow warning message for bitand expression
2020-05-14 19:51 [Bug c/95141] New: Incorrect integer overflow warning message for bitand expression yadongh at vt dot edu
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2020-05-20 7:42 ` [Bug c/95141] [8/9/10 " rguenth at gcc dot gnu.org
@ 2020-06-23 11:06 ` cvs-commit at gcc dot gnu.org
2020-06-23 11:08 ` [Bug c/95141] [8/9 " rguenth at gcc dot gnu.org
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From: cvs-commit at gcc dot gnu.org @ 2020-06-23 11:06 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95141
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:
https://gcc.gnu.org/g:cc08609b62ed37d279c986ebb9cb8294eb4e0e3b
commit r10-8351-gcc08609b62ed37d279c986ebb9cb8294eb4e0e3b
Author: Richard Biener <rguenther@suse.de>
Date: Tue May 19 07:58:33 2020 +0200
c/95141 - fix bogus integer overflow warning
This fixes an integer overflow warning that ultimatively happens because
of TREE_OVERFLOW propagating through transforms and the existing guard
against this,
375 if (TREE_OVERFLOW_P (ret)
376 && !TREE_OVERFLOW_P (op0)
377 && !TREE_OVERFLOW_P (op1))
378 overflow_warning (EXPR_LOC_OR_LOC (expr, input_location,
being insufficient. Rather than trying to use sth like walk_tree to
exhaustively walk operands (with the possibility of introducing
quadraticness when folding larger expressions recursively) the
following amends the above with an ad-hoc test for a binary op0
with a possibly constant op1.
2020-05-30 Richard Biener <rguenther@suse.de>
PR c/95141
gcc/c
* c-fold.c (c_fully_fold_internal): Enhance guard on
overflow_warning.
gcc/testsuite
* gcc.dg/pr95141.c: New testcase.
^ permalink raw reply [flat|nested] 11+ messages in thread* [Bug c/95141] [8/9 Regression] Incorrect integer overflow warning message for bitand expression
2020-05-14 19:51 [Bug c/95141] New: Incorrect integer overflow warning message for bitand expression yadongh at vt dot edu
` (5 preceding siblings ...)
2020-06-23 11:06 ` cvs-commit at gcc dot gnu.org
@ 2020-06-23 11:08 ` rguenth at gcc dot gnu.org
2021-05-14 9:53 ` [Bug c/95141] [9 " jakub at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2020-06-23 11:08 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95141
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P3 |P2
Summary|[8/9/10 Regression] |[8/9 Regression] Incorrect
|Incorrect integer overflow |integer overflow warning
|warning message for bitand |message for bitand
|expression |expression
Known to work| |10.1.1
^ permalink raw reply [flat|nested] 11+ messages in thread* [Bug c/95141] [9 Regression] Incorrect integer overflow warning message for bitand expression
2020-05-14 19:51 [Bug c/95141] New: Incorrect integer overflow warning message for bitand expression yadongh at vt dot edu
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2020-06-23 11:08 ` [Bug c/95141] [8/9 " rguenth at gcc dot gnu.org
@ 2021-05-14 9:53 ` jakub at gcc dot gnu.org
2021-06-01 8:17 ` rguenth at gcc dot gnu.org
2022-05-27 8:52 ` rguenth at gcc dot gnu.org
9 siblings, 0 replies; 11+ messages in thread
From: jakub at gcc dot gnu.org @ 2021-05-14 9:53 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95141
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|8.5 |9.4
--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 8 branch is being closed.
^ permalink raw reply [flat|nested] 11+ messages in thread* [Bug c/95141] [9 Regression] Incorrect integer overflow warning message for bitand expression
2020-05-14 19:51 [Bug c/95141] New: Incorrect integer overflow warning message for bitand expression yadongh at vt dot edu
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2021-05-14 9:53 ` [Bug c/95141] [9 " jakub at gcc dot gnu.org
@ 2021-06-01 8:17 ` rguenth at gcc dot gnu.org
2022-05-27 8:52 ` rguenth at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2021-06-01 8:17 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95141
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|9.4 |9.5
--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 9.4 is being released, retargeting bugs to GCC 9.5.
^ permalink raw reply [flat|nested] 11+ messages in thread* [Bug c/95141] [9 Regression] Incorrect integer overflow warning message for bitand expression
2020-05-14 19:51 [Bug c/95141] New: Incorrect integer overflow warning message for bitand expression yadongh at vt dot edu
` (8 preceding siblings ...)
2021-06-01 8:17 ` rguenth at gcc dot gnu.org
@ 2022-05-27 8:52 ` rguenth at gcc dot gnu.org
9 siblings, 0 replies; 11+ messages in thread
From: rguenth at gcc dot gnu.org @ 2022-05-27 8:52 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95141
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|ASSIGNED |RESOLVED
Target Milestone|9.5 |10.2
Known to fail| |9.5.0
--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed for GCC 10.2.
^ permalink raw reply [flat|nested] 11+ messages in thread