[Bug middle-end/17564] [4.0 Regression] New treatment of function pointers when used with equality operators, when casts are involved
--- Additional Comments From cvs-commit at gcc dot gnu dot org 2004-12-12 21:01 --- Subject: Bug 17564 CVSROOT:/cvs/gcc Module name:gcc Changes by: [EMAIL PROTECTED] 2004-12-12 21:01:17 Modified files: gcc: ChangeLog dojump.c Log message: PR middle-end/17564 * dojump.c (do_compare_and_jump): Only canonicalize function pointers in a comparison if both sides are function pointers. Patches: http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gccr1=2.6793r2=2.6794 http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/dojump.c.diff?cvsroot=gccr1=1.33r2=1.34 -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17564
[Bug middle-end/17564] [4.0 Regression] New treatment of function pointers when used with equality operators, when casts are involved
--- Additional Comments From cvs-commit at gcc dot gnu dot org 2004-12-13 04:08 --- Subject: Bug 17564 CVSROOT:/cvs/gcc Module name:gcc Changes by: [EMAIL PROTECTED] 2004-12-13 04:08:40 Modified files: gcc/testsuite : ChangeLog Added files: gcc/testsuite/gcc.c-torture/execute: 20041212-1.c Log message: PR middle-end/17564 * gcc.c-torture/execute/20041212-1.c: New test. Patches: http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gccr1=1.4742r2=1.4743 http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gcc.c-torture/execute/20041212-1.c.diff?cvsroot=gccr1=NONEr2=1.1 -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17564
[Bug middle-end/17564] [4.0 Regression] New treatment of function pointers when used with equality operators, when casts are involved
--- Additional Comments From danglin at gcc dot gnu dot org 2004-12-12 21:19 --- Fixed by patch. -- What|Removed |Added Status|NEW |RESOLVED Resolution||FIXED http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17564
[Bug middle-end/17564] [4.0 Regression] New treatment of function pointers when used with equality operators, when casts are involved
--- Additional Comments From dave at hiauly1 dot hia dot nrc dot ca 2004-12-05 22:43 --- Subject: Re: [4.0 Regression] New treatment of function Nathanael, Do you think we could canonicalize only when we compare a function pointer to a function pointer (rather than when comparing a function pointer to a void pointer)? Would that do the trick, or would it lead to further trouble? Tentative, untested patch attached. I seem to have used a version of gcc without your patch when I checked it with the PR testcase. Would you please submit it to gcc-patches as a fix for the PR? The patch has a parenthesis typo that needs fixing. Dave -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17564
[Bug middle-end/17564] [4.0 Regression] New treatment of function pointers when used with equality operators, when casts are involved
--- Additional Comments From dave at hiauly1 dot hia dot nrc dot ca 2004-11-30 03:42 --- Subject: Re: [4.0 Regression] New treatment of function Do you think we could canonicalize only when we compare a function pointer to a function pointer (rather than when comparing a function pointer to a void pointer)? Would that do the trick, or would it lead to further trouble? Tentative, untested patch attached. This provides some improvement (i.e., it fixes the testsuite fail that prompted the PR) but the testcase that I submitted with the PR still fails. I need to investigate why the function pointer in the comparison is still getting canonicalized. Dave -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17564
[Bug middle-end/17564] [4.0 Regression] New treatment of function pointers when used with equality operators, when casts are involved
--- Additional Comments From dave at hiauly1 dot hia dot nrc dot ca 2004-11-28 23:16 --- Subject: Re: [4.0 Regression] New treatment of function Do you think we could canonicalize only when we compare a function pointer to a function pointer (rather than when comparing a function pointer to a void pointer)? Would that do the trick, or would it lead to further trouble? That seems correct to me. Similarly, we wouldn't want canonicalization when comparing a function pointer with an integer. Tentative, untested patch attached. I'll give it a try. Dave -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17564
[Bug middle-end/17564] [4.0 Regression] New treatment of function pointers when used with equality operators, when casts are involved
--- Additional Comments From neroden at gcc dot gnu dot org 2004-11-27 00:53 --- I'm going to guess that one solution is to canonicalize any function pointer any time it's cast to a void pointer. (Or do you really, really want noncanonicalized pointers, which is likely to be harder?) This probably requires recognition at tree level that casts from function pointer to void pointer may be necessary (among other things). From tree_ssa_useless_type_conversion_1 in tree_ssa.c: /* If both types are pointers and the outer type is a (void *), then the conversion is not necessary. The opposite is not true since that conversion would result in a loss of information if the equivalence was used. Consider an indirect function call where we need to know the exact type of the function to correctly implement the ABI. */ else if (POINTER_TYPE_P (inner_type) POINTER_TYPE_P (outer_type) TYPE_MODE (inner_type) == TYPE_MODE (outer_type) TYPE_REF_CAN_ALIAS_ALL (inner_type) == TYPE_REF_CAN_ALIAS_ALL (outer_type) TREE_CODE (TREE_TYPE (outer_type)) == VOID_TYPE) return true; So it seems that this type conversion isn't useless when converting from a function pointer to a void pointer (on targets where function pointers need canonicalization); it requires a canonicalization. (Or a forcing of non-canonicalization, which sounds harder.) Confirming. -- What|Removed |Added Status|UNCONFIRMED |NEW Ever Confirmed||1 Last reconfirmed|-00-00 00:00:00 |2004-11-27 00:53:19 date|| Summary|[4.0 Regression] New|[4.0 Regression] New |treatment of function |treatment of function |pointers when used with |pointers when used with |equality operators |equality operators, when ||casts are involved http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17564
[Bug middle-end/17564] [4.0 Regression] New treatment of function pointers when used with equality operators, when casts are involved
--- Additional Comments From dave at hiauly1 dot hia dot nrc dot ca
2004-11-27 04:09 ---
Subject: Re: [4.0 Regression] New treatment of function
--- Additional Comments From neroden at gcc dot gnu dot org 2004-11-27
00:53 ---
I'm going to guess that one solution is to canonicalize any function pointer
any time it's cast to a void pointer. (Or do you really, really want
noncanonicalized pointers, which is likely to be harder?)
I believe we really want noncanonicalized pointers. For example, the
following code works in 3.4 (i.e., a function pointer cast to void
pointer and back to a function pointer yields a function pointer that
can be used in a call to a compatible function):
void *f (void) __attribute__ ((__noinline__));
void *
f (void)
{
return f;
}
int
main (void)
{
void * (*g) (void) = f ();
if (g () != f)
abort ();
exit (0);
}
If the call to f returned a canonicalized value, the call using g
would fail if the target was in a shared library (external). The
PIC register wouldn't be correctly set.
Dave
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17564
[Bug middle-end/17564] [4.0 Regression] New treatment of function pointers when used with equality operators
-- What|Removed |Added CC||tausq at debian dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17564
