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* [Bug c/32099] New: a constant value is said to be not constant @ 2007-05-26 18:15 andrei dot kouznetsov at gmail dot com 2007-05-26 18:27 ` [Bug c/32099] " pinskia at gcc dot gnu dot org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: andrei dot kouznetsov at gmail dot com @ 2007-05-26 18:15 UTC (permalink / raw) To: gcc-bugs [-- Warning: decoded text below may be mangled, UTF-8 assumed --] [-- Attachment #1: Type: text/plain, Size: 1360 bytes --] when I'm trying to compile the program ============================ #include <math.h> static double s = sin(0.0); int main(){ return 0; } ============================ with gcc t.c, the compiler produces the warnings t.c:3: warning: initializer element is not constant t.c:3: warning: (near initialization for s) t.c:3: warning: s defined but not used I'm worried about the first warning, since sin(0) is constant gcc -v generates: ======================================= Using built-in specs. Target: i486-linux-gnu Configured with: ../src/configure -v --enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr --enable-shared --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --enable-nls --program-suffix=-4.1 --enable-__cxa_atexit --enable-clocale=gnu --enable-libstdcxx-debug --enable-mpfr --enable-checking=release i486-linux-gnu Thread model: posix gcc version 4.1.2 (Ubuntu 4.1.2-0ubuntu4) -- Summary: a constant value is said to be not constant Product: gcc Version: 4.1.2 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: andrei dot kouznetsov at gmail dot com http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32099 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/32099] a constant value is said to be not constant 2007-05-26 18:15 [Bug c/32099] New: a constant value is said to be not constant andrei dot kouznetsov at gmail dot com @ 2007-05-26 18:27 ` pinskia at gcc dot gnu dot org 2007-05-26 18:47 ` andrei dot kouznetsov at gmail dot com ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu dot org @ 2007-05-26 18:27 UTC (permalink / raw) To: gcc-bugs ------- Comment #1 from pinskia at gcc dot gnu dot org 2007-05-26 18:26 ------- No, sin(0) is not constant in C. C has specific rules about constant expression. You can use __builtin_sin(0) to always get the constant folding. -- pinskia at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution| |INVALID http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32099 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/32099] a constant value is said to be not constant 2007-05-26 18:15 [Bug c/32099] New: a constant value is said to be not constant andrei dot kouznetsov at gmail dot com 2007-05-26 18:27 ` [Bug c/32099] " pinskia at gcc dot gnu dot org @ 2007-05-26 18:47 ` andrei dot kouznetsov at gmail dot com 2007-05-28 12:54 ` manu at gcc dot gnu dot org 2007-06-10 3:23 ` [Bug middle-end/32099] not constant folding sin pinskia at gcc dot gnu dot org 3 siblings, 0 replies; 5+ messages in thread From: andrei dot kouznetsov at gmail dot com @ 2007-05-26 18:47 UTC (permalink / raw) To: gcc-bugs ------- Comment #2 from andrei dot kouznetsov at gmail dot com 2007-05-26 18:47 ------- Ok, but __builtin_sin(M_PI) is not constant again -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32099 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/32099] a constant value is said to be not constant 2007-05-26 18:15 [Bug c/32099] New: a constant value is said to be not constant andrei dot kouznetsov at gmail dot com 2007-05-26 18:27 ` [Bug c/32099] " pinskia at gcc dot gnu dot org 2007-05-26 18:47 ` andrei dot kouznetsov at gmail dot com @ 2007-05-28 12:54 ` manu at gcc dot gnu dot org 2007-06-10 3:23 ` [Bug middle-end/32099] not constant folding sin pinskia at gcc dot gnu dot org 3 siblings, 0 replies; 5+ messages in thread From: manu at gcc dot gnu dot org @ 2007-05-28 12:54 UTC (permalink / raw) To: gcc-bugs ------- Comment #3 from manu at gcc dot gnu dot org 2007-05-28 12:54 ------- Worse, with __builtin_sin(M_PI), I get an error: test.c:2: error: initializer element is not constant Maybe this is fixed now in GCC 4.3 by using MPFR. -- manu at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |manu at gcc dot gnu dot org Status|RESOLVED |UNCONFIRMED Resolution|INVALID | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32099 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/32099] not constant folding sin 2007-05-26 18:15 [Bug c/32099] New: a constant value is said to be not constant andrei dot kouznetsov at gmail dot com ` (2 preceding siblings ...) 2007-05-28 12:54 ` manu at gcc dot gnu dot org @ 2007-06-10 3:23 ` pinskia at gcc dot gnu dot org 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu dot org @ 2007-06-10 3:23 UTC (permalink / raw) To: gcc-bugs ------- Comment #4 from pinskia at gcc dot gnu dot org 2007-06-10 03:23 ------- This is an extension that GCC allows some constant folding with some functions. So this is just a missed optimization of not constant folding sin. And yes this is fixed in 4.3.0 by the use of MPFR. -- pinskia at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Component|c |middle-end Keywords| |missed-optimization Resolution| |FIXED Summary|a constant value is said to |not constant folding sin |be not constant | Target Milestone|--- |4.3.0 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32099 ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2007-06-10 3:23 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2007-05-26 18:15 [Bug c/32099] New: a constant value is said to be not constant andrei dot kouznetsov at gmail dot com 2007-05-26 18:27 ` [Bug c/32099] " pinskia at gcc dot gnu dot org 2007-05-26 18:47 ` andrei dot kouznetsov at gmail dot com 2007-05-28 12:54 ` manu at gcc dot gnu dot org 2007-06-10 3:23 ` [Bug middle-end/32099] not constant folding sin pinskia at gcc dot gnu dot org
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