Here's a minimal test-case: ---------
int copysign_bug(double x) { if (x * 0.5 == x) return 1; else if (copysign(1.0, x) < 0.0) return 2; else return 3; } int main(void) { double x; x = -0.0; printf("copysign_bug(%.17g) = %d\n", x, copysign_bug(x)); x = 0.0; printf("copysign_bug(%.17g) = %d\n", x, copysign_bug(x)); return 0; } ------- I'm compiling and executing the above code (filename copysign_bug.c) on OpenSolaris build snv_134 running in Parallels on a Macbook Pro (Intel Core 2 Duo), using the following command line: gcc-4.4 -m64 -fno-inline -g -O3 copysign_bug.c -o copysign_bug && ./copysign_bug I get the results: copysign_bug(-0) = 3 copysign_bug(0) = 3 I was expecting to see the results: copysign_bug(-0) = 2 copysign_bug(0) = 3 I get the latter results if I omit the '-O3' flag, or if I compile with -fno-builtin-copysign and link with the math library. gcc build information: dicki...@eratosthenes:~/trunk$ gcc-4.4 -v -save-temps -m64 -lm -fno-builtin-copysign -fno-inline -g copysign_bug.c Using built-in specs. Target: i386-pc-solaris2.11 Configured with: ../gcc-4.4.4/configure --prefix=/usr/local --program-suffix=-4.4 --with-mpfr-include=/usr/include/mpfr --with-gmp-include=/usr/include/gmp --with-as=/usr/bin/gas --with-gnu-as --with-ld=/usr/bin/ld --without-gnu-ld --enable-shared --enable-multilib --enable-languages=c,c++,objc Thread model: posix gcc version 4.4.4 (GCC) COLLECT_GCC_OPTIONS='-v' '-save-temps' '-m64' '-fno-builtin-copysign' '-fno-inline' '-g' '-mtune=generic' /usr/local/libexec/gcc/i386-pc-solaris2.11/4.4.4/cc1 -E -quiet -v -imultilib amd64 copysign_bug.c -m64 -mtune=generic -fno-builtin-copysign -fno-inline -g -fworking-directory -fpch-preprocess -o copysign_bug.i ignoring nonexistent directory "/usr/local/lib/gcc/i386-pc-solaris2.11/4.4.4/../../../../i386-pc-solaris2.11/include" #include "..." search starts here: #include <...> search starts here: /usr/local/include /usr/local/lib/gcc/i386-pc-solaris2.11/4.4.4/include /usr/local/lib/gcc/i386-pc-solaris2.11/4.4.4/include-fixed /usr/include End of search list. COLLECT_GCC_OPTIONS='-v' '-save-temps' '-m64' '-fno-builtin-copysign' '-fno-inline' '-g' '-mtune=generic' /usr/local/libexec/gcc/i386-pc-solaris2.11/4.4.4/cc1 -fpreprocessed copysign_bug.i -quiet -dumpbase copysign_bug.c -m64 -mtune=generic -auxbase copysign_bug -g -version -fno-builtin-copysign -fno-inline -o copysign_bug.s GNU C (GCC) version 4.4.4 (i386-pc-solaris2.11) compiled by GNU C version 4.4.4, GMP version 4.3.1, MPFR version 2.4.1-p5. GGC heuristics: --param ggc-min-expand=99 --param ggc-min-heapsize=131015 Compiler executable checksum: f408a824c22e56e60b321448197fb865 COLLECT_GCC_OPTIONS='-v' '-save-temps' '-m64' '-fno-builtin-copysign' '-fno-inline' '-g' '-mtune=generic' /usr/bin/gas -v -V -Qy --64 -s -o copysign_bug.o copysign_bug.s GNU assembler version 2.19 (i386-pc-solaris2.11) using BFD version (GNU Binutils) 2.19 COMPILER_PATH=/usr/local/libexec/gcc/i386-pc-solaris2.11/4.4.4/:/usr/local/libexec/gcc/i386-pc-solaris2.11/4.4.4/:/usr/local/libexec/gcc/i386-pc-solaris2.11/:/usr/local/lib/gcc/i386-pc-solaris2.11/4.4.4/:/usr/local/lib/gcc/i386-pc-solaris2.11/:/usr/ccs/bin/ LIBRARY_PATH=/usr/local/lib/gcc/i386-pc-solaris2.11/4.4.4/amd64/:/usr/local/lib/gcc/i386-pc-solaris2.11/4.4.4/../../../amd64/:/lib/amd64/:/usr/lib/amd64/:/usr/local/lib/gcc/i386-pc-solaris2.11/4.4.4/:/usr/local/lib/gcc/i386-pc-solaris2.11/4.4.4/../../../:/lib/:/usr/lib/ COLLECT_GCC_OPTIONS='-v' '-save-temps' '-m64' '-fno-builtin-copysign' '-fno-inline' '-g' '-mtune=generic' /usr/local/libexec/gcc/i386-pc-solaris2.11/4.4.4/collect2 -V -Y P,/lib/64:/usr/lib/64 -Qy /usr/lib/amd64/crt1.o /usr/lib/amd64/crti.o /usr/lib/amd64/values-Xa.o /usr/local/lib/gcc/i386-pc-solaris2.11/4.4.4/amd64/crtbegin.o -L/usr/local/lib/gcc/i386-pc-solaris2.11/4.4.4/amd64 -L/usr/local/lib/gcc/i386-pc-solaris2.11/4.4.4/../../../amd64 -L/lib/amd64 -L/usr/lib/amd64 -L/usr/local/lib/gcc/i386-pc-solaris2.11/4.4.4 -L/usr/local/lib/gcc/i386-pc-solaris2.11/4.4.4/../../.. -lm copysign_bug.o -lgcc -lgcc_eh -lc -lgcc -lgcc_eh /usr/local/lib/gcc/i386-pc-solaris2.11/4.4.4/amd64/crtend.o /usr/lib/amd64/crtn.o ld: Software Generation Utilities - Solaris Link Editors: 5.11-1.1689 -- Summary: Optimization bug with copysign builtin Product: gcc Version: 4.4.4 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: dickinsm at gmail dot com GCC build triplet: i386-pc-solaris2.11 GCC host triplet: i386-pc-solaris2.11 GCC target triplet: i386-pc-solaris2.11 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44683