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c/3752: gcc 3.0: __builtin_constant_p(ptr==ptr), regression
- To: gcc-gnats at gcc dot gnu dot org
- Subject: c/3752: gcc 3.0: __builtin_constant_p(ptr==ptr), regression
- From: Kevin Ryde <user42 at zip dot com dot au>
- Date: 21 Jul 2001 07:27:36 +1000
>Number: 3752
>Category: c
>Synopsis: gcc 3.0: __builtin_constant_p(ptr==ptr), regression
>Confidential: yes
>Severity: non-critical
>Priority: medium
>Responsible: unassigned
>State: open
>Class: pessimizes-code
>Submitter-Id: net
>Arrival-Date: Fri Jul 20 14:36:03 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:
>Release: 3.0 (Debian) (Debian testing/unstable)
>Organization:
>Environment:
System: Linux blah 2.2.15 #1 Tue Apr 25 17:13:48 EST 2000 i586 unknown
Architecture: i586
<machine, os, target, libraries (multiple lines)>
host: i386-pc-linux-gnu
build: i386-pc-linux-gnu
target: i386-pc-linux-gnu
configured with: ../src/configure -v --enable-languages=c,c++,java,f77,proto,objc --prefix=/usr --infodir=/share/info --mandir=/share/man --enable-shared --with-gnu-as --with-gnu-ld --with-system-zlib --enable-long-long --enable-nls --without-included-gettext --disable-checking --enable-threads=posix --enable-java-gc=boehm --with-cpp-install-dir=bin --enable-objc-gc i386-linux
>Description:
gcc 3 __builtin_constant_p fails to recognise "ptr==ptr" as a
constant, whereas gcc 2.95.x did.
>How-To-Repeat:
A program foo.c
int
main (int argc, char **argv)
{
printf ("%d\n", __builtin_constant_p (argv == argv));
return 0;
}
compiled with
gcc-3.0 -O9 foo.c
prints "0" whereas I might have hoped it could print "1" since
argv==argv can certainly be known at compile time.
Curiously, using "argc" instead of "argv" gives the hoped-for "1".
Also a gcc 2.95.4 pre-release gives "1" in both cases.
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted: