input: ====== a.c ===== #include <stdio.h> #include <inttypes.h>
int main() { uint64_t pos = 1; pos = 1; if (pos < 1 || pos > 0xffffffffffffffffULL) { printf("fail\n"); return 1; } printf("ok\n"); return 0; } ===== end of a.c ===== command lines: $ gcc a.c $ ./a.out ok $ gcc -O a.c $ ./a.out fail assembler code for comparison of pos is not generated correctly. it should test, at least, pos < 1, but generated code act like if the condition was true. if "pos > 0xffffffffffffffffUL" is not present, it runs successfully. definitely, optimization bug while preevaluating the condition at compile time. my gcc version information is: $ gcc -v Reading specs from /usr/lib/gcc/i686-pc-linux-gnu/3.4.3-20050110/specs Configured with: /var/tmp/portage/gcc-3.4.3.20050110-r2/work/gcc-3.4.3/configure --enable-version-specific-runtime-libs --prefix=/usr --bindir=/usr/i686-pc-linux-gnu/gcc-bin/3.4.3-20050110 --includedir=/usr/lib/gcc/i686-pc-linux-gnu/3.4.3-20050110/include --datadir=/usr/share/gcc-data/i686-pc-linux-gnu/3.4.3-20050110 --mandir=/usr/share/gcc-data/i686-pc-linux-gnu/3.4.3-20050110/man --infodir=/usr/share/gcc-data/i686-pc-linux-gnu/3.4.3-20050110/info --with-gxx-include-dir=/usr/lib/gcc/i686-pc-linux-gnu/3.4.3-20050110/include/g++-v3 --host=i686-pc-linux-gnu --disable-altivec --enable-nls --without-included-gettext --with-system-zlib --disable-checking --disable-werror --disable-libunwind-exceptions --disable-multilib --disable-libgcj --enable-languages=c,c++,f77 --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu Thread model: posix gcc version 3.4.3-20050110 (Gentoo Linux 3.4.3.20050110-r2, ssp-3.4.3.20050110-0, pie-8.7.7) -- Summary: assembler code is not generated for uint64_t comparison with -O Product: gcc Version: 3.4.3 Status: UNCONFIRMED Severity: normal Priority: P2 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: moonz at kaist dot ac dot kr CC: gcc-bugs at gcc dot gnu dot org GCC build triplet: i686-pc-linux-gnu GCC host triplet: i686-pc-linux-gnu GCC target triplet: i686-pc-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21464