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* [Bug c/24931] New: uninitialized structure member after assignment
@ 2005-11-18 5:53 dylan at dylex dot net
2005-11-18 6:19 ` [Bug tree-optimization/24931] [4.0/4.1 Regression] " pinskia at gcc dot gnu dot org
` (7 more replies)
0 siblings, 8 replies; 9+ messages in thread
From: dylan at dylex dot net @ 2005-11-18 5:53 UTC (permalink / raw)
To: gcc-bugs
Consider this code:
struct p {
short x, y;
};
struct s {
int i;
struct p p;
};
struct s f()
{
struct s s;
s.p = (struct p){};
s.i = (s.p.x || s.p.y);
return s;
}
When compiled with gcc -Wall -O -c, it reports:
t.c: In function 'f':
t.c:14: warning: 's.i' is used uninitialized in this function
That's not right. Furthermore, I think the generated assembly might be wrong
(this is with -O):
f:
movl $0, %eax
ret
The return value should be a full 64 bits (%rax), but only the bottom 32 are
initialized (unless this clears the high ones on x86_64 or the calling
convention says they are already -- I don't really know).
--
Summary: uninitialized structure member after assignment
Product: gcc
Version: 4.0.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: dylan at dylex dot net
GCC build triplet: x86_64-pc-linux-gnu
GCC host triplet: x86_64-pc-linux-gnu
GCC target triplet: x86_64-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24931
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/24931] [4.0/4.1 Regression] uninitialized structure member after assignment
2005-11-18 5:53 [Bug c/24931] New: uninitialized structure member after assignment dylan at dylex dot net
@ 2005-11-18 6:19 ` pinskia at gcc dot gnu dot org
2005-11-19 2:21 ` mmitchel at gcc dot gnu dot org
` (6 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-11-18 6:19 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from pinskia at gcc dot gnu dot org 2005-11-18 06:19 -------
First this is a very bogus warning.
Second this is caused by SRA and BIT_FIELD_REF:
D.1509.x = 0;
D.1509.y = 0;
s.p = D.1509;
D.1511_10 = BIT_FIELD_REF <s, 32, 32>;
D.1512_12 = D.1511_10 != 0;
s.i = D.1512_12;
D.1513 = s;
The problem is that SRA does not look into seeing if s.i is needed so it does:
SR.25_11 = 0;
SR.24_26 = 0;
s$p$y_27 = SR.24_26;
s$p$x_28 = SR.25_11;
s.i = s$i_29;
s.p.y = s$p$y_27;
s.p.x = s$p$x_28;
D.1511_10 = BIT_FIELD_REF <s, 32, 32>;
D.1512_12 = D.1511_10 != 0;
s$i_33 = D.1512_12;
s.i = s$i_33;
s.p.y = s$p$y_27;
s.p.x = s$p$x_28;
D.1513 = s;
The wrong code part is not really wrong code, just a misunderstanding of what
the instruction does:
(insn 43 40 49 (set (reg/i:DI 0 ax [ <result> ])
(const_int 0 [0x0])) 81 {*movdi_1_rex64} (insn_list:REG_DEP_TRUE 35
(nil))
(nil))
It sign extends to the full register which means rax is 0 and not just the
bottom part.
Hmm, even the struct aliasing code does not know either:
# VUSE <SFT.3_7>;
# VUSE <SFT.4_8>;
# VUSE <SFT.5_9>;
D.1511_10 = BIT_FIELD_REF <s, 32, 32>;
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |rth at gcc dot gnu dot org,
| |dberlin at gcc dot gnu dot
| |org
OtherBugsDependingO| |24639
nThis| |
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
GCC build triplet|x86_64-pc-linux-gnu |
GCC host triplet|x86_64-pc-linux-gnu |
GCC target triplet|x86_64-pc-linux-gnu |x86_64-*-* i?86-*-*
Last reconfirmed|0000-00-00 00:00:00 |2005-11-18 06:19:39
date| |
Summary|uninitialized structure |[4.0/4.1 Regression]
|member after assignment |uninitialized structure
| |member after assignment
Target Milestone|--- |4.0.3
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24931
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/24931] [4.0/4.1 Regression] uninitialized structure member after assignment
2005-11-18 5:53 [Bug c/24931] New: uninitialized structure member after assignment dylan at dylex dot net
2005-11-18 6:19 ` [Bug tree-optimization/24931] [4.0/4.1 Regression] " pinskia at gcc dot gnu dot org
@ 2005-11-19 2:21 ` mmitchel at gcc dot gnu dot org
2005-11-20 20:08 ` rth at gcc dot gnu dot org
` (5 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: mmitchel at gcc dot gnu dot org @ 2005-11-19 2:21 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from mmitchel at gcc dot gnu dot org 2005-11-19 02:21 -------
This is annoying warning; let's fix.
--
mmitchel at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P3 |P2
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24931
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/24931] [4.0/4.1 Regression] uninitialized structure member after assignment
2005-11-18 5:53 [Bug c/24931] New: uninitialized structure member after assignment dylan at dylex dot net
2005-11-18 6:19 ` [Bug tree-optimization/24931] [4.0/4.1 Regression] " pinskia at gcc dot gnu dot org
2005-11-19 2:21 ` mmitchel at gcc dot gnu dot org
@ 2005-11-20 20:08 ` rth at gcc dot gnu dot org
2005-11-21 0:51 ` [Bug tree-optimization/24931] [4.0/4.1/4.2 " rth at gcc dot gnu dot org
` (4 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: rth at gcc dot gnu dot org @ 2005-11-20 20:08 UTC (permalink / raw)
To: gcc-bugs
--
rth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
AssignedTo|unassigned at gcc dot gnu |rth at gcc dot gnu dot org
|dot org |
Status|NEW |ASSIGNED
Last reconfirmed|2005-11-18 06:19:39 |2005-11-20 20:08:55
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24931
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/24931] [4.0/4.1/4.2 Regression] uninitialized structure member after assignment
2005-11-18 5:53 [Bug c/24931] New: uninitialized structure member after assignment dylan at dylex dot net
` (2 preceding siblings ...)
2005-11-20 20:08 ` rth at gcc dot gnu dot org
@ 2005-11-21 0:51 ` rth at gcc dot gnu dot org
2005-11-21 0:56 ` rth at gcc dot gnu dot org
` (3 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: rth at gcc dot gnu dot org @ 2005-11-21 0:51 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from rth at gcc dot gnu dot org 2005-11-21 00:51 -------
Subject: Bug 24931
Author: rth
Date: Mon Nov 21 00:51:39 2005
New Revision: 107271
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=107271
Log:
PR 24931
* tree-sra.c (struct sra_elt): Add all_no_warning.
(struct sra_walk_fns) <use>: Add use_all argument.
(sra_walk_expr): Pass it.
(sra_walk_modify_expr): Likewise.
(scalarize_ldst): Likewise.
(scan_use): Update for new argument.
(mark_no_warning): New.
(scalarize_use): Use it.
Added:
trunk/gcc/testsuite/gcc.dg/uninit-14.c
Modified:
trunk/gcc/ChangeLog
trunk/gcc/tree-sra.c
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24931
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/24931] [4.0/4.1/4.2 Regression] uninitialized structure member after assignment
2005-11-18 5:53 [Bug c/24931] New: uninitialized structure member after assignment dylan at dylex dot net
` (3 preceding siblings ...)
2005-11-21 0:51 ` [Bug tree-optimization/24931] [4.0/4.1/4.2 " rth at gcc dot gnu dot org
@ 2005-11-21 0:56 ` rth at gcc dot gnu dot org
2005-11-22 0:06 ` [Bug tree-optimization/24931] [4.0 " pinskia at gcc dot gnu dot org
` (2 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: rth at gcc dot gnu dot org @ 2005-11-21 0:56 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from rth at gcc dot gnu dot org 2005-11-21 00:56 -------
Subject: Bug 24931
Author: rth
Date: Mon Nov 21 00:55:57 2005
New Revision: 107272
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=107272
Log:
PR 24931
* tree-sra.c (struct sra_elt): Add all_no_warning.
(struct sra_walk_fns) <use>: Add use_all argument.
(sra_walk_expr): Pass it.
(sra_walk_modify_expr): Likewise.
(scalarize_ldst): Likewise.
(scan_use): Update for new argument.
(mark_no_warning): New.
(scalarize_use): Use it.
Added:
branches/gcc-4_1-branch/gcc/testsuite/gcc.dg/uninit-14.c
- copied unchanged from r107271, trunk/gcc/testsuite/gcc.dg/uninit-14.c
Modified:
branches/gcc-4_1-branch/gcc/ChangeLog
branches/gcc-4_1-branch/gcc/tree-sra.c
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24931
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/24931] [4.0 Regression] uninitialized structure member after assignment
2005-11-18 5:53 [Bug c/24931] New: uninitialized structure member after assignment dylan at dylex dot net
` (4 preceding siblings ...)
2005-11-21 0:56 ` rth at gcc dot gnu dot org
@ 2005-11-22 0:06 ` pinskia at gcc dot gnu dot org
2006-03-11 3:19 ` mmitchel at gcc dot gnu dot org
2007-02-03 16:02 ` gdr at gcc dot gnu dot org
7 siblings, 0 replies; 9+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-11-22 0:06 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from pinskia at gcc dot gnu dot org 2005-11-22 00:06 -------
Fixed at least on the mainline and 4.1 branch for now.
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Known to fail| |4.0.0 4.0.2
Known to work| |4.1.0 4.2.0 3.4.4
Summary|[4.0/4.1/4.2 Regression] |[4.0 Regression]
|uninitialized structure |uninitialized structure
|member after assignment |member after assignment
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24931
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/24931] [4.0 Regression] uninitialized structure member after assignment
2005-11-18 5:53 [Bug c/24931] New: uninitialized structure member after assignment dylan at dylex dot net
` (5 preceding siblings ...)
2005-11-22 0:06 ` [Bug tree-optimization/24931] [4.0 " pinskia at gcc dot gnu dot org
@ 2006-03-11 3:19 ` mmitchel at gcc dot gnu dot org
2007-02-03 16:02 ` gdr at gcc dot gnu dot org
7 siblings, 0 replies; 9+ messages in thread
From: mmitchel at gcc dot gnu dot org @ 2006-03-11 3:19 UTC (permalink / raw)
To: gcc-bugs
--
mmitchel at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|4.0.3 |4.0.4
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24931
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/24931] [4.0 Regression] uninitialized structure member after assignment
2005-11-18 5:53 [Bug c/24931] New: uninitialized structure member after assignment dylan at dylex dot net
` (6 preceding siblings ...)
2006-03-11 3:19 ` mmitchel at gcc dot gnu dot org
@ 2007-02-03 16:02 ` gdr at gcc dot gnu dot org
7 siblings, 0 replies; 9+ messages in thread
From: gdr at gcc dot gnu dot org @ 2007-02-03 16:02 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from gdr at gcc dot gnu dot org 2007-02-03 16:02 -------
Fixed in GCC-4.1.0
--
gdr at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
Target Milestone|4.0.4 |4.1.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24931
^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2007-02-03 16:02 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
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2005-11-18 5:53 [Bug c/24931] New: uninitialized structure member after assignment dylan at dylex dot net
2005-11-18 6:19 ` [Bug tree-optimization/24931] [4.0/4.1 Regression] " pinskia at gcc dot gnu dot org
2005-11-19 2:21 ` mmitchel at gcc dot gnu dot org
2005-11-20 20:08 ` rth at gcc dot gnu dot org
2005-11-21 0:51 ` [Bug tree-optimization/24931] [4.0/4.1/4.2 " rth at gcc dot gnu dot org
2005-11-21 0:56 ` rth at gcc dot gnu dot org
2005-11-22 0:06 ` [Bug tree-optimization/24931] [4.0 " pinskia at gcc dot gnu dot org
2006-03-11 3:19 ` mmitchel at gcc dot gnu dot org
2007-02-03 16:02 ` gdr at gcc dot gnu dot org
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