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* [Bug c++/11667] New: wider-than-ine enums never compare equal to 0
@ 2003-07-25 2:48 aoliva at gcc dot gnu dot org
2003-07-25 2:49 ` [Bug c++/11667] " aoliva at gcc dot gnu dot org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: aoliva at gcc dot gnu dot org @ 2003-07-25 2:48 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11667
Summary: wider-than-ine enums never compare equal to 0
Product: gcc
Version: 3.4
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c++
AssignedTo: mark at codesourcery dot com
ReportedBy: aoliva at gcc dot gnu dot org
CC: gcc-bugs at gcc dot gnu dot org
GCC host triplet: an
Mark,
Your patch for PR 10796, that implemented C++ DR377, also contained a
code clean-up that was actually wrong. The underlying type of an enum
must be an integral type, but, after your patch, we end up with a type
whose precision is given by the min and max values of the enumeration,
that doesn't necessarily match the precision of any of the integral
types.
Richard Sandiford found out we were miscompiling libstdc++ because of
this, and I turned the code snippet he extracted from libstdc++ into
the attached testcase. Richard also analyzed the problem in detail,
but it turned out that he didn't know for sure what had been decided
for DR377, so I ended up taking the issue over and found out the exact
bits of Mark's patch that introduced the problem but didn't contribute
to the implementation of the DR or the fix to the PR.
<quote author="Richard Sandiford">
When compiling "gx == 0", we call shorten_compare with:
op0 = <nop_expr type <integer_type SI> arg 0 <var_decl gx>>
op1 = <integer_cst type <int> constant 0>
result_type = <integer_type SI>
The first thing shorten_compare does is to remove integer promotions, so:
primop0 = <var_decl gx>
primop1 = <integer_cst type <int> constant 0>
We then have:
/* If comparing an integer against a constant more bits wide,
maybe we can deduce a value of 1 or 0 independent of the data.
Or else truncate the constant now
rather than extend the variable at run time.
This is only interesting if the constant is the wider arg.
Also, it is not safe if the constant is unsigned and the
variable arg is signed, since in this case the variable
would be sign-extended and then regarded as unsigned.
Our technique fails in this case because the lowest/highest
possible unsigned results don't follow naturally from the
lowest/highest possible values of the variable operand.
For just EQ_EXPR and NE_EXPR there is another technique that
could be used: see if the constant can be faithfully represented
in the other operand's type, by truncating it and reextending it
and see if that preserves the constant's value. */
if (!real1 && !real2
&& TREE_CODE (primop1) == INTEGER_CST
&& TYPE_PRECISION (TREE_TYPE (primop0)) < TYPE_PRECISION (*restype_ptr))
{
int min_gt, max_gt, min_lt, max_lt;
tree maxval, minval;
/* 1 if comparison is nominally unsigned. */
int unsignedp = TREE_UNSIGNED (*restype_ptr);
tree val;
type = c_common_signed_or_unsigned_type (unsignedp0,
TREE_TYPE (primop0));
/* If TYPE is an enumeration, then we need to get its min/max
values from it's underlying integral type, not the enumerated
type itself. */
if (TREE_CODE (type) == ENUMERAL_TYPE)
---> type = c_common_type_for_size (TYPE_PRECISION (type), unsignedp0);
Before Mark's patch, TYPE_PRECISION (TREE_TYPE (gx)) was 32, so this
code wasn't executed. But now gx's precision is 17.
At the indicated line, "type" becomes the unsigned version of the
underlying type (i.e. an unsigned SI type). We then convert the
minimum and maximum values of this type into the "common type",
which is signed in this case:
maxval = TYPE_MAX_VALUE (type);
minval = TYPE_MIN_VALUE (type);
[...]
if (type != *restype_ptr)
{
minval = convert (*restype_ptr, minval);
maxval = convert (*restype_ptr, maxval);
}
maxval is now -1 and any non-negative number seems out of range.
</quote>
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/11667] wider-than-ine enums never compare equal to 0
2003-07-25 2:48 [Bug c++/11667] New: wider-than-ine enums never compare equal to 0 aoliva at gcc dot gnu dot org
@ 2003-07-25 2:49 ` aoliva at gcc dot gnu dot org
2003-07-25 2:50 ` pinskia at gcc dot gnu dot org
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: aoliva at gcc dot gnu dot org @ 2003-07-25 2:49 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11667
------- Additional Comments From aoliva at gcc dot gnu dot org 2003-07-25 02:49 -------
Created an attachment (id=4477)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=4477&action=view)
Patch that reverts the part of Mark's patch that causes the new test added by
the patch to fail
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/11667] wider-than-ine enums never compare equal to 0
2003-07-25 2:48 [Bug c++/11667] New: wider-than-ine enums never compare equal to 0 aoliva at gcc dot gnu dot org
2003-07-25 2:49 ` [Bug c++/11667] " aoliva at gcc dot gnu dot org
2003-07-25 2:50 ` pinskia at gcc dot gnu dot org
@ 2003-07-25 2:50 ` aoliva at gcc dot gnu dot org
2003-07-29 1:14 ` [Bug c++/11667] wider-than-int " cvs-commit at gcc dot gnu dot org
2003-07-29 1:18 ` mmitchel at gcc dot gnu dot org
4 siblings, 0 replies; 6+ messages in thread
From: aoliva at gcc dot gnu dot org @ 2003-07-25 2:50 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11667
aoliva at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed| |1
Last reconfirmed|0000-00-00 00:00:00 |2003-07-25 02:50:07
date| |
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/11667] wider-than-ine enums never compare equal to 0
2003-07-25 2:48 [Bug c++/11667] New: wider-than-ine enums never compare equal to 0 aoliva at gcc dot gnu dot org
2003-07-25 2:49 ` [Bug c++/11667] " aoliva at gcc dot gnu dot org
@ 2003-07-25 2:50 ` pinskia at gcc dot gnu dot org
2003-07-25 2:50 ` aoliva at gcc dot gnu dot org
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2003-07-25 2:50 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11667
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Last reconfirmed|2003-07-25 02:50:07 |2003-07-25 02:50:56
date| |
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/11667] wider-than-int enums never compare equal to 0
2003-07-25 2:48 [Bug c++/11667] New: wider-than-ine enums never compare equal to 0 aoliva at gcc dot gnu dot org
` (2 preceding siblings ...)
2003-07-25 2:50 ` aoliva at gcc dot gnu dot org
@ 2003-07-29 1:14 ` cvs-commit at gcc dot gnu dot org
2003-07-29 1:18 ` mmitchel at gcc dot gnu dot org
4 siblings, 0 replies; 6+ messages in thread
From: cvs-commit at gcc dot gnu dot org @ 2003-07-29 1:14 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11667
------- Additional Comments From cvs-commit at gcc dot gnu dot org 2003-07-29 01:14 -------
Subject: Bug 11667
CVSROOT: /cvs/gcc
Module name: gcc
Changes by: mmitchel@gcc.gnu.org 2003-07-29 01:14:25
Modified files:
gcc : ChangeLog c-common.c stor-layout.c tree.h
gcc/cp : ChangeLog Make-lang.in call.c class.c decl.c
pt.c rtti.c typeck.c
gcc/testsuite : ChangeLog
gcc/testsuite/g++.dg/template: overload1.C
Added files:
gcc/testsuite/g++.dg/init: enum2.C
Log message:
PR c++/11667
* c-common.c (shorten_compare): Take into account differences
between C and C++ representation for enumeration types.
* tree.h (set_min_and_max_values_for_integral_type): Declare.
* stor-layout.c (set_min_and_max_values_for_integral_type): New
function, broken out from ...
(fixup_signed_type): ... here and ...
(fixup_unsigned_type): ... here.
PR c++/11667
* call.c (standard_conversion): Allow all integral->enumeral
conversions, after marking them as bad.
* decl.c (finish_enum): Make sure that all enumerators are
properly converted to the underlying type.
(build_enumerator): Set DECL_CONTEXT for namespace-scope
enumeration types.
* pt.c (tsubst_copy): Adjust handling of CONST_DECLs accordingly.
(tsubst_enum): Tidy.
* Make-lang.in (typeck.o): Depend on convert.h.
(class.o): Likewise.
(rtti.o): Likewise.
* call.c: Include convert.h.
(convert_arg_to_ellipsis): Use convert_to_real.
* class.c: Include convert.h.
(build_base_path): Use convert_to_integer.
* rtti.c: Include convert.h.
(build_headof): Use convert_to_integer.
* typeck.c: Include convert.h.
(decay_conversion): Use convert_to_integer.
(build_unary_op): Use build_nop.
(get_delta_difference): Use convert_to_integer.
(build_ptrmemfunc): Avoid unncessary conversions.
Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.641&r2=2.642
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/c-common.c.diff?cvsroot=gcc&r1=1.439&r2=1.440
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/stor-layout.c.diff?cvsroot=gcc&r1=1.164&r2=1.165
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/tree.h.diff?cvsroot=gcc&r1=1.430&r2=1.431
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/ChangeLog.diff?cvsroot=gcc&r1=1.3563&r2=1.3564
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/Make-lang.in.diff?cvsroot=gcc&r1=1.158&r2=1.159
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/call.c.diff?cvsroot=gcc&r1=1.416&r2=1.417
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/class.c.diff?cvsroot=gcc&r1=1.557&r2=1.558
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/decl.c.diff?cvsroot=gcc&r1=1.1102&r2=1.1103
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/pt.c.diff?cvsroot=gcc&r1=1.740&r2=1.741
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/rtti.c.diff?cvsroot=gcc&r1=1.170&r2=1.171
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/typeck.c.diff?cvsroot=gcc&r1=1.487&r2=1.488
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&r1=1.2925&r2=1.2926
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/init/enum2.C.diff?cvsroot=gcc&r1=1.1&r2=1.2
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/template/overload1.C.diff?cvsroot=gcc&r1=1.1&r2=1.2
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/11667] wider-than-int enums never compare equal to 0
2003-07-25 2:48 [Bug c++/11667] New: wider-than-ine enums never compare equal to 0 aoliva at gcc dot gnu dot org
` (3 preceding siblings ...)
2003-07-29 1:14 ` [Bug c++/11667] wider-than-int " cvs-commit at gcc dot gnu dot org
@ 2003-07-29 1:18 ` mmitchel at gcc dot gnu dot org
4 siblings, 0 replies; 6+ messages in thread
From: mmitchel at gcc dot gnu dot org @ 2003-07-29 1:18 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11667
mmitchel at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
------- Additional Comments From mmitchel at gcc dot gnu dot org 2003-07-29 01:18 -------
Fixed in GCC 3.4.
^ permalink raw reply [flat|nested] 6+ messages in thread
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2003-07-25 2:48 [Bug c++/11667] New: wider-than-ine enums never compare equal to 0 aoliva at gcc dot gnu dot org
2003-07-25 2:49 ` [Bug c++/11667] " aoliva at gcc dot gnu dot org
2003-07-25 2:50 ` pinskia at gcc dot gnu dot org
2003-07-25 2:50 ` aoliva at gcc dot gnu dot org
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