* [Bug c++/38851] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
@ 2009-01-14 21:05 ` nvachhar at google dot com
2009-01-14 21:58 ` pinskia at gcc dot gnu dot org
` (19 subsequent siblings)
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From: nvachhar at google dot com @ 2009-01-14 21:05 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from nvachhar at google dot com 2009-01-14 21:05 -------
Created an attachment (id=17104)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17104&action=view)
Test case program
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug c++/38851] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
2009-01-14 21:05 ` [Bug c++/38851] " nvachhar at google dot com
@ 2009-01-14 21:58 ` pinskia at gcc dot gnu dot org
2009-01-21 22:19 ` [Bug middle-end/38851] [4.3 regression] " bkoz at gcc dot gnu dot org
` (18 subsequent siblings)
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From: pinskia at gcc dot gnu dot org @ 2009-01-14 21:58 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from pinskia at gcc dot gnu dot org 2009-01-14 21:58 -------
other.c_ = c;
The issue here is that MyCompare is an empty struct (but has a sizeof of 1
because C++ standard) but GCC is not deleting stores for some reason.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.3 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
2009-01-14 21:05 ` [Bug c++/38851] " nvachhar at google dot com
2009-01-14 21:58 ` pinskia at gcc dot gnu dot org
@ 2009-01-21 22:19 ` bkoz at gcc dot gnu dot org
2009-01-21 22:41 ` [Bug middle-end/38851] [4.4 " bkoz at gcc dot gnu dot org
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From: bkoz at gcc dot gnu dot org @ 2009-01-21 22:19 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from bkoz at gcc dot gnu dot org 2009-01-21 22:19 -------
Confirmed for s390x.
This is causing the following s390x libstdc++ testsuite failures, and is thus a
regression from 4.3. As far as I can tell these warnings are spurious.
http://gcc.gnu.org/ml/gcc-testresults/2009-01/msg02102.html
And from the libstdc++.log file:
FAIL: 27_io/ios_base/types/fmtflags/bitmask_operators.cc (test for excess
errors)
Excess errors:
/build-extralong/BUILD/gcc/libstdc++-v3/testsuite/util/testsuite_common_types.h:401:
warning: 'a' is used uninitialized in this function
/build-extralong/BUILD/gcc/libstdc++-v3/testsuite/util/testsuite_common_types.h:401:
warning: 'b' is used uninitialized in this function
/build-extralong/BUILD/gcc/libstdc++-v3/testsuite/util/testsuite_common_types.h:413:
warning: 'b' is used uninitialized in this function
FAIL: 27_io/ios_base/types/iostate/bitmask_operators.cc (test for excess
errors)
/build-extralong/BUILD/gcc/libstdc++-v3/testsuite/util/testsuite_common_types.h:401:
warning: 'a' is used uninitialized in this function
/build-extralong/BUILD/gcc/libstdc++-v3/testsuite/util/testsuite_common_types.h:401:
warning: 'b' is used uninitialized in this function
/build-extralong/BUILD/gcc/libstdc++-v3/testsuite/util/testsuite_common_types.h:413:
warning: 'b' is used uninitialized in this function
FAIL: 27_io/ios_base/types/openmode/bitmask_operators.cc (test for excess
errors)
/build-extralong/BUILD/gcc/libstdc++-v3/testsuite/util/testsuite_common_types.h:401:
warning: 'a' is used uninitialized in this function
/build-extralong/BUILD/gcc/libstdc++-v3/testsuite/util/testsuite_common_types.h:401:
warning: 'b' is used uninitialized in this function
/build-extralong/BUILD/gcc/libstdc++-v3/testsuite/util/testsuite_common_types.h:413:
warning: 'b' is used uninitialized in this function
--
bkoz at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |bkoz at gcc dot gnu dot org
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2009-01-21 22:19:31
date| |
Summary|Compiler warns about |[4.3 regression] Compiler
|uninitialized variable that |warns about uninitialized
|is an object with a |variable that is an object
|constructor |with a constructor
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (2 preceding siblings ...)
2009-01-21 22:19 ` [Bug middle-end/38851] [4.3 regression] " bkoz at gcc dot gnu dot org
@ 2009-01-21 22:41 ` bkoz at gcc dot gnu dot org
2009-01-21 22:49 ` [Bug c++/38851] " rguenth at gcc dot gnu dot org
` (16 subsequent siblings)
20 siblings, 0 replies; 22+ messages in thread
From: bkoz at gcc dot gnu dot org @ 2009-01-21 22:41 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from bkoz at gcc dot gnu dot org 2009-01-21 22:41 -------
fixed summary
--
bkoz at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Known to work| |4.3.2
Summary|[4.3 regression] Compiler |[4.4 regression] Compiler
|warns about uninitialized |warns about uninitialized
|variable that is an object |variable that is an object
|with a constructor |with a constructor
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug c++/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (3 preceding siblings ...)
2009-01-21 22:41 ` [Bug middle-end/38851] [4.4 " bkoz at gcc dot gnu dot org
@ 2009-01-21 22:49 ` rguenth at gcc dot gnu dot org
2009-01-21 22:59 ` [Bug middle-end/38851] " pinskia at gcc dot gnu dot org
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From: rguenth at gcc dot gnu dot org @ 2009-01-21 22:49 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from rguenth at gcc dot gnu dot org 2009-01-21 22:49 -------
I think it is the frontends business to omit the stores.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|middle-end |c++
Keywords| |diagnostic, missed-
| |optimization
Priority|P3 |P2
Target Milestone|--- |4.4.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (4 preceding siblings ...)
2009-01-21 22:49 ` [Bug c++/38851] " rguenth at gcc dot gnu dot org
@ 2009-01-21 22:59 ` pinskia at gcc dot gnu dot org
2009-01-23 19:32 ` bangerth at dealii dot org
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From: pinskia at gcc dot gnu dot org @ 2009-01-21 22:59 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from pinskia at gcc dot gnu dot org 2009-01-21 22:59 -------
(In reply to comment #5)
> I think it is the frontends business to omit the stores.
Or the gimplifier like what happens for GNU C code:
/* For zero sized types only gimplify the left hand side and right hand
side as statements and throw away the assignment. Do this after
gimplify_modify_expr_rhs so we handle TARGET_EXPRs of addressable
types properly. */
The reason why it does not do it for C++ code is because the struct's size are
really 1 instead of 0.
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|c++ |middle-end
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (5 preceding siblings ...)
2009-01-21 22:59 ` [Bug middle-end/38851] " pinskia at gcc dot gnu dot org
@ 2009-01-23 19:32 ` bangerth at dealii dot org
2009-01-24 9:22 ` rguenth at gcc dot gnu dot org
` (13 subsequent siblings)
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From: bangerth at dealii dot org @ 2009-01-23 19:32 UTC (permalink / raw)
To: gcc-bugs
------- Comment #7 from bangerth at dealii dot org 2009-01-23 19:31 -------
I see this as well. It triggers a lot when using boost::graph which
uses empty classes as tags all over the place. A simple case with
boost::graph would be this:
--------------------------
#include <boost/graph/adjacency_list.hpp>
using namespace boost;
adjacency_list<vecS, vecS, undirectedS,
property<vertex_color_t, default_color_type,
property<vertex_degree_t,int> > > g;
void create_graph () { add_edge(1,2, g); }
--------------------------
boost/graph/detail/adjacency_list.hpp: In function 'void create_graph()':
boost/graph/detail/adjacency_list.hpp:819: warning: 'p' may be used
uninitialized in this function
boost/graph/detail/adjacency_list.hpp:2210: note: 'p' was declared here
This problem makes -Wuninitialize pretty much useless for anyone who uses
boost::graph. I think it would be a shame if we shipped a compiler that
has a problem with this.
W.
--
bangerth at dealii dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |mmitchel at gcc dot gnu dot
| |org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (6 preceding siblings ...)
2009-01-23 19:32 ` bangerth at dealii dot org
@ 2009-01-24 9:22 ` rguenth at gcc dot gnu dot org
2009-01-24 9:27 ` rguenth at gcc dot gnu dot org
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From: rguenth at gcc dot gnu dot org @ 2009-01-24 9:22 UTC (permalink / raw)
To: gcc-bugs
------- Comment #8 from rguenth at gcc dot gnu dot org 2009-01-24 09:22 -------
Smaller testcase:
struct Empty { Empty() {} };
struct Other {
Other(const Empty& e_) : e(e_) {}
Empty e;
};
void bar(Other&);
void foo()
{
Empty e;
Other o(e);
bar(o);
}
RTL expansion removes the assignment, so we should be able to use the same
reasoning to disable the warning and/or to get rid of the assignment on
the tree level. RTL uses expr_size() here, which yields const0_rtx for e
and o. As this involves a langhook I think the correct thing is to fix
the missed-optimization and remove these stores during gimplification
(or from within the frontend, of course).
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |lopezibanez at gmail dot
| |com, rguenth at gcc dot gnu
| |dot org
Priority|P2 |P1
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (7 preceding siblings ...)
2009-01-24 9:22 ` rguenth at gcc dot gnu dot org
@ 2009-01-24 9:27 ` rguenth at gcc dot gnu dot org
2009-01-24 10:06 ` rguenth at gcc dot gnu dot org
` (11 subsequent siblings)
20 siblings, 0 replies; 22+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2009-01-24 9:27 UTC (permalink / raw)
To: gcc-bugs
------- Comment #9 from rguenth at gcc dot gnu dot org 2009-01-24 09:27 -------
I am testing the following.
@@ -4195,7 +4184,8 @@ gimplify_modify_expr (tree *expr_p, gimp
side as statements and throw away the assignment. Do this after
gimplify_modify_expr_rhs so we handle TARGET_EXPRs of addressable
types properly. */
- if (zero_sized_type (TREE_TYPE (*from_p)) && !want_value)
+ if (int_expr_size (*from_p) == 0
+ && !want_value)
{
gimplify_stmt (from_p, pre_p);
gimplify_stmt (to_p, pre_p);
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
AssignedTo|unassigned at gcc dot gnu |rguenth at gcc dot gnu dot
|dot org |org
Status|NEW |ASSIGNED
Last reconfirmed|2009-01-21 22:19:31 |2009-01-24 09:27:19
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (8 preceding siblings ...)
2009-01-24 9:27 ` rguenth at gcc dot gnu dot org
@ 2009-01-24 10:06 ` rguenth at gcc dot gnu dot org
2009-01-24 14:23 ` rguenth at gcc dot gnu dot org
` (10 subsequent siblings)
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From: rguenth at gcc dot gnu dot org @ 2009-01-24 10:06 UTC (permalink / raw)
To: gcc-bugs
------- Comment #10 from rguenth at gcc dot gnu dot org 2009-01-24 10:06 -------
Bah, the C++ frontend can return NULL_TREE from its expr_size langhook. How
bad of it.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (9 preceding siblings ...)
2009-01-24 10:06 ` rguenth at gcc dot gnu dot org
@ 2009-01-24 14:23 ` rguenth at gcc dot gnu dot org
2009-01-24 14:24 ` rguenth at gcc dot gnu dot org
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From: rguenth at gcc dot gnu dot org @ 2009-01-24 14:23 UTC (permalink / raw)
To: gcc-bugs
------- Comment #11 from rguenth at gcc dot gnu dot org 2009-01-24 14:23 -------
Created an attachment (id=17175)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17175&action=view)
semi-working patch
Patch. Regresses
=== g++ tests ===
Running target unix
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 51)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 59)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 60)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 61)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 62)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 66)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 74)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 75)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 76)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 77)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 78)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 79)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 83)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 91)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 92)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 93)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 94)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 98)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 106)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 107)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 108)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 109)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 110)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 111)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 115)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 123)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 124)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 125)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 126)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 130)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 138)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 139)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 140)
FAIL: g++.dg/cpp0x/rv1n.C (test for errors, line 141)
FAIL: g++.dg/cpp0x/rv1n.C (test for excess errors)
FAIL: g++.dg/cpp0x/rv1p.C (test for excess errors)
... (some more of these)
FAIL: g++.dg/cpp0x/rv7n.C (test for errors, line 83)
FAIL: g++.dg/cpp0x/rv7n.C (test for excess errors)
FAIL: g++.dg/cpp0x/rv7p.C (test for excess errors)
FAIL: g++.dg/cpp0x/rv8p.C (test for excess errors)
FAIL: g++.old-deja/g++.other/empty1.C execution test
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (10 preceding siblings ...)
2009-01-24 14:23 ` rguenth at gcc dot gnu dot org
@ 2009-01-24 14:24 ` rguenth at gcc dot gnu dot org
2009-01-25 18:02 ` rguenth at gcc dot gnu dot org
` (8 subsequent siblings)
20 siblings, 0 replies; 22+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2009-01-24 14:24 UTC (permalink / raw)
To: gcc-bugs
------- Comment #12 from rguenth at gcc dot gnu dot org 2009-01-24 14:24 -------
Probably because the FE looks into the gimplified code again? Well -
unassigning.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
AssignedTo|rguenth 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=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (11 preceding siblings ...)
2009-01-24 14:24 ` rguenth at gcc dot gnu dot org
@ 2009-01-25 18:02 ` rguenth at gcc dot gnu dot org
2009-01-25 19:45 ` mmitchel at gcc dot gnu dot org
` (7 subsequent siblings)
20 siblings, 0 replies; 22+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2009-01-25 18:02 UTC (permalink / raw)
To: gcc-bugs
------- Comment #13 from rguenth at gcc dot gnu dot org 2009-01-25 18:02 -------
*** Bug 38908 has been marked as a duplicate of this bug. ***
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |simon_baldwin at yahoo dot
| |com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (12 preceding siblings ...)
2009-01-25 18:02 ` rguenth at gcc dot gnu dot org
@ 2009-01-25 19:45 ` mmitchel at gcc dot gnu dot org
2009-01-25 20:00 ` rguenther at suse dot de
` (6 subsequent siblings)
20 siblings, 0 replies; 22+ messages in thread
From: mmitchel at gcc dot gnu dot org @ 2009-01-25 19:45 UTC (permalink / raw)
To: gcc-bugs
------- Comment #14 from mmitchel at gcc dot gnu dot org 2009-01-25 19:45 -------
Richard --
I don't agree that it's necessarily the FE's job to omit all stores to such
types. Our general theory is that FEs get to emit dumb code and the optimizers
get to fix it up. Of course, I don't object to making the FE generate simpler
code, if that's easy to do; just that if our design relies on that, I think
that's a mistake.
I can imagine ways this could come up in other languages as well. For example,
copying a C structure with an anonymous bit-field, but no other content, or an
Ada record that uses Ada's layout directives to control size.
Therefore, I don't think that the key here is "zero-size". Instead, it's the
fact that structure cannot be initialized. That's useful both for warnings and
for optimization; it can't be initialized, so there's no point about warning
about uninitialized uses, and there's no reason to actually generate code for
the copies.
That leads to something I do think is something that the FEs could be asked to
do: set a bit on the type to indicate that it is uninitializable or, if you
like, logically empty.
I also don't see this as a P1 defect. It's certainly annoying, but,
fundamentally, it limits the utility of a warning which has been known to give
false positives for a long time. Important to fix, yes -- but as important as
generating wrong code?
-- Mark
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (13 preceding siblings ...)
2009-01-25 19:45 ` mmitchel at gcc dot gnu dot org
@ 2009-01-25 20:00 ` rguenther at suse dot de
2009-01-25 20:04 ` mark at codesourcery dot com
` (5 subsequent siblings)
20 siblings, 0 replies; 22+ messages in thread
From: rguenther at suse dot de @ 2009-01-25 20:00 UTC (permalink / raw)
To: gcc-bugs
------- Comment #15 from rguenther at suse dot de 2009-01-25 19:59 -------
Subject: Re: [4.4 regression] Compiler warns about
uninitialized variable that is an object with a constructor
On Sun, 25 Jan 2009, mmitchel at gcc dot gnu dot org wrote:
> ------- Comment #14 from mmitchel at gcc dot gnu dot org 2009-01-25 19:45 -------
> Richard --
>
> I don't agree that it's necessarily the FE's job to omit all stores to such
> types. Our general theory is that FEs get to emit dumb code and the optimizers
> get to fix it up. Of course, I don't object to making the FE generate simpler
> code, if that's easy to do; just that if our design relies on that, I think
> that's a mistake.
Oh, I agree. See my attempt to fix it during gimplification.
> I can imagine ways this could come up in other languages as well. For example,
> copying a C structure with an anonymous bit-field, but no other content, or an
> Ada record that uses Ada's layout directives to control size.
>
> Therefore, I don't think that the key here is "zero-size". Instead, it's the
> fact that structure cannot be initialized. That's useful both for warnings and
> for optimization; it can't be initialized, so there's no point about warning
> about uninitialized uses, and there's no reason to actually generate code for
> the copies.
Ok, I think mapping cannot be initialized to zero-size is ok, as that is
the only thing we can currently query (and we even specialize this
for C++ to deal with the 1 byte vs. empty case).
> That leads to something I do think is something that the FEs could be asked to
> do: set a bit on the type to indicate that it is uninitializable or, if you
> like, logically empty.
>
> I also don't see this as a P1 defect. It's certainly annoying, but,
> fundamentally, it limits the utility of a warning which has been known to give
> false positives for a long time. Important to fix, yes -- but as important as
> generating wrong code?
It's a P1 defect as we didn't warn for uninitialized structure
uses in any previous relelase. While we can argue that it is safe
to downgrade this to P2 I think we should at least try to fix this
issue for 4.4.0.
Richard.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (14 preceding siblings ...)
2009-01-25 20:00 ` rguenther at suse dot de
@ 2009-01-25 20:04 ` mark at codesourcery dot com
2009-01-25 20:45 ` rguenther at suse dot de
` (4 subsequent siblings)
20 siblings, 0 replies; 22+ messages in thread
From: mark at codesourcery dot com @ 2009-01-25 20:04 UTC (permalink / raw)
To: gcc-bugs
------- Comment #16 from mark at codesourcery dot com 2009-01-25 20:03 -------
Subject: Re: [4.4 regression] Compiler warns about
uninitialized variable that is an object with a constructor
rguenther at suse dot de wrote:
>> Therefore, I don't think that the key here is "zero-size". Instead, it's the
>> fact that structure cannot be initialized. That's useful both for warnings and
>> for optimization; it can't be initialized, so there's no point about warning
>> about uninitialized uses, and there's no reason to actually generate code for
>> the copies.
>
> Ok, I think mapping cannot be initialized to zero-size is ok, as that is
> the only thing we can currently query (and we even specialize this
> for C++ to deal with the 1 byte vs. empty case).
Yes, I think it's OK to approximate "logically empty" by "zero-size" at
present. It might be worth either changing the zero-size
documentation/name to reflect that it means "logically empty" (if we
think these are the same concept) or else defining a separate
LOGICALLY_EMPTY_P predicate (implemented by checking for zero size) as a
hedge against separating them (if we think they are usefully distinct
concepts).
> It's a P1 defect as we didn't warn for uninitialized structure
> uses in any previous relelase. While we can argue that it is safe
> to downgrade this to P2 I think we should at least try to fix this
> issue for 4.4.0.
I don't mind fixing it, of course, and it would certainly be better to
do so. But, at the end of the day, if everything else is ready, I'd be
opposed to holding up the release for this.
Thanks,
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (15 preceding siblings ...)
2009-01-25 20:04 ` mark at codesourcery dot com
@ 2009-01-25 20:45 ` rguenther at suse dot de
2009-01-25 22:03 ` rguenth at gcc dot gnu dot org
` (3 subsequent siblings)
20 siblings, 0 replies; 22+ messages in thread
From: rguenther at suse dot de @ 2009-01-25 20:45 UTC (permalink / raw)
To: gcc-bugs
------- Comment #17 from rguenther at suse dot de 2009-01-25 20:45 -------
Subject: Re: [4.4 regression] Compiler warns about
uninitialized variable that is an object with a constructor
On Sun, 25 Jan 2009, mark at codesourcery dot com wrote:
> ------- Comment #16 from mark at codesourcery dot com 2009-01-25 20:03 -------
> Subject: Re: [4.4 regression] Compiler warns about
> uninitialized variable that is an object with a constructor
>
> rguenther at suse dot de wrote:
>
> > It's a P1 defect as we didn't warn for uninitialized structure
> > uses in any previous relelase. While we can argue that it is safe
> > to downgrade this to P2 I think we should at least try to fix this
> > issue for 4.4.0.
>
> I don't mind fixing it, of course, and it would certainly be better to
> do so. But, at the end of the day, if everything else is ready, I'd be
> opposed to holding up the release for this.
I agree. Sometimes having one more priority inbetween P2 and P1 would
be nice ;)
Richard.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (16 preceding siblings ...)
2009-01-25 20:45 ` rguenther at suse dot de
@ 2009-01-25 22:03 ` rguenth at gcc dot gnu dot org
2009-01-26 9:53 ` rguenth at gcc dot gnu dot org
` (2 subsequent siblings)
20 siblings, 0 replies; 22+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2009-01-25 22:03 UTC (permalink / raw)
To: gcc-bugs
------- Comment #18 from rguenth at gcc dot gnu dot org 2009-01-25 22:02 -------
I am testing another patch, improving simple-DSE instead.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
AssignedTo|unassigned at gcc dot gnu |rguenth at gcc dot gnu dot
|dot org |org
Status|NEW |ASSIGNED
Last reconfirmed|2009-01-24 09:27:19 |2009-01-25 22:02:56
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (17 preceding siblings ...)
2009-01-25 22:03 ` rguenth at gcc dot gnu dot org
@ 2009-01-26 9:53 ` rguenth at gcc dot gnu dot org
2009-01-26 9:53 ` rguenth at gcc dot gnu dot org
2009-01-30 17:32 ` hjl at gcc dot gnu dot org
20 siblings, 0 replies; 22+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2009-01-26 9:53 UTC (permalink / raw)
To: gcc-bugs
------- Comment #19 from rguenth at gcc dot gnu dot org 2009-01-26 09:53 -------
Subject: Bug 38851
Author: rguenth
Date: Mon Jan 26 09:52:48 2009
New Revision: 143672
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=143672
Log:
2009-01-26 Richard Guenther <rguenther@suse.de>
PR middle-end/38851
* Makefile.in (tree-ssa-dse.o): Add langhooks.h.
* tree-ssa-dse.c: Include langhooks.h
(execute_simple_dse): Remove stores with zero size.
* g++.dg/warn/Wuninitialized-1.C: New testcase.
Added:
trunk/gcc/testsuite/g++.dg/warn/Wuninitialized-1.C
Modified:
trunk/gcc/ChangeLog
trunk/gcc/Makefile.in
trunk/gcc/testsuite/ChangeLog
trunk/gcc/tree-ssa-dse.c
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (18 preceding siblings ...)
2009-01-26 9:53 ` rguenth at gcc dot gnu dot org
@ 2009-01-26 9:53 ` rguenth at gcc dot gnu dot org
2009-01-30 17:32 ` hjl at gcc dot gnu dot org
20 siblings, 0 replies; 22+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2009-01-26 9:53 UTC (permalink / raw)
To: gcc-bugs
------- Comment #20 from rguenth at gcc dot gnu dot org 2009-01-26 09:53 -------
Fixed.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread
* [Bug middle-end/38851] [4.4 regression] Compiler warns about uninitialized variable that is an object with a constructor
2009-01-14 21:04 [Bug c++/38851] New: Compiler warns about uninitialized variable that is an object with a constructor nvachhar at google dot com
` (19 preceding siblings ...)
2009-01-26 9:53 ` rguenth at gcc dot gnu dot org
@ 2009-01-30 17:32 ` hjl at gcc dot gnu dot org
20 siblings, 0 replies; 22+ messages in thread
From: hjl at gcc dot gnu dot org @ 2009-01-30 17:32 UTC (permalink / raw)
To: gcc-bugs
------- Comment #21 from hjl at gcc dot gnu dot org 2009-01-30 17:32 -------
Subject: Bug 38851
Author: hjl
Date: Fri Jan 30 17:31:24 2009
New Revision: 143798
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=143798
Log:
2009-01-30 H.J. Lu <hongjiu.lu@intel.com>
2009-01-27 Richard Guenther <rguenther@suse.de>
PR tree-optimization/38503
* g++.dg/warn/Wstrict-aliasing-bogus-placement-new.C: New testcase.
2009-01-26 Richard Guenther <rguenther@suse.de>
PR tree-optimization/38745
* g++.dg/torture/pr38745.C: New testcase.
2009-01-26 Richard Guenther <rguenther@suse.de>
PR middle-end/38851
* g++.dg/warn/Wuninitialized-1.C: New testcase.
2009-01-20 Andrew Pinski <andrew_pinski@playstation.sony.com>
Richard Guenther <rguenther@suse.de>
PR tree-optimization/38747
PR tree-optimization/38748
* gcc.dg/tree-ssa/struct-aliasing-1.c: New test.
* gcc.c-torture/execute/struct-aliasing-1.c: Likewise.
Added:
branches/gcc-4_3-branch/gcc/testsuite/g++.dg/torture/pr38745.C
- copied unchanged from r143797,
trunk/gcc/testsuite/g++.dg/torture/pr38745.C
branches/gcc-4_3-branch/gcc/testsuite/g++.dg/warn/Wstrict-aliasing-bogus-placement-new.C
- copied unchanged from r143797,
trunk/gcc/testsuite/g++.dg/warn/Wstrict-aliasing-bogus-placement-new.C
branches/gcc-4_3-branch/gcc/testsuite/g++.dg/warn/Wuninitialized-1.C
- copied unchanged from r143797,
trunk/gcc/testsuite/g++.dg/warn/Wuninitialized-1.C
branches/gcc-4_3-branch/gcc/testsuite/gcc.c-torture/execute/struct-aliasing-1.c
- copied unchanged from r143797,
trunk/gcc/testsuite/gcc.c-torture/execute/struct-aliasing-1.c
branches/gcc-4_3-branch/gcc/testsuite/gcc.dg/tree-ssa/struct-aliasing-1.c
- copied unchanged from r143797,
trunk/gcc/testsuite/gcc.dg/tree-ssa/struct-aliasing-1.c
Modified:
branches/gcc-4_3-branch/gcc/testsuite/ChangeLog
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38851
^ permalink raw reply [flat|nested] 22+ messages in thread