| Summary: | Invalid code with O2 flag (bad alias analysis?) | ||
|---|---|---|---|
| Product: | gcc | Reporter: | nicos |
| Component: | c | Assignee: | Not yet assigned to anyone <unassigned> |
| Status: | RESOLVED DUPLICATE | ||
| Severity: | normal | CC: | gcc-bugs |
| Priority: | P2 | ||
| Version: | 3.4.4 | ||
| Target Milestone: | --- | ||
| Host: | Target: | ||
| Build: | Known to work: | ||
| Known to fail: | Last reconfirmed: | ||
Source code: #include <stdio.h> int main (int argc, char * argv[]) { unsigned int t[2] = {1, 1}; *((double *)t) = 0.0; printf("%d\n", t[1]); } This code prints "1" insted of "0" when with: gcc foo.c -o foo -O2 Output of gcc -v foo.c -o foo2 -O2: Reading specs from /usr/lib/gcc/i686-pc-linux-gnu/3.4.4/specs Configured with: /var/tmp/portage/gcc-3.4.4/work/gcc-3.4.4/configure --enable-version-specific-runtime-libs --prefix=/usr --bindir=/usr/i686-pc-linux-gnu/gcc-bin/3.4.4 --includedir=/usr/lib/gcc/i686-pc-linux-gnu/3.4.4/include --datadir=/usr/share/gcc-data/i686-pc-linux-gnu/3.4.4 --mandir=/usr/share/gcc-data/i686-pc-linux-gnu/3.4.4/man --infodir=/usr/share/gcc-data/i686-pc-linux-gnu/3.4.4/info --with-gxx-include-dir=/usr/lib/gcc/i686-pc-linux-gnu/3.4.4/include/g++-v3 --host=i686-pc-linux-gnu --build=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 3.4.4 (Gentoo 3.4.4, ssp-3.4.4-1.0, pie-8.7.8) /usr/libexec/gcc/i686-pc-linux-gnu/3.4.4/cc1 -quiet -v foo.c -quiet -dumpbase foo.c -mtune=pentiumpro -auxbase foo -O2 -version -o /tmp/ccFePbg2.s ignoring nonexistent directory "/usr/local/include" ignoring nonexistent directory "/usr/lib/gcc/i686-pc-linux-gnu/3.4.4/../../../../i686-pc-linux-gnu/include" #include "..." search starts here: #include <...> search starts here: /usr/lib/gcc/i686-pc-linux-gnu/3.4.4/include /usr/include End of search list. GNU C version 3.4.4 (Gentoo 3.4.4, ssp-3.4.4-1.0, pie-8.7.8) (i686-pc-linux-gnu) compiled by GNU C version 3.4.4 (Gentoo 3.4.4, ssp-3.4.4-1.0, pie-8.7.8). GGC heuristics: --param ggc-min-expand=90 --param ggc-min-heapsize=113127 /usr/lib/gcc/i686-pc-linux-gnu/3.4.4/../../../../i686-pc-linux-gnu/bin/as -V -Qy -o /tmp/ccokr9zW.o /tmp/ccFePbg2.s GNU assembler version 2.16.1 (i686-pc-linux-gnu) using BFD version 2.16.1 /usr/libexec/gcc/i686-pc-linux-gnu/3.4.4/collect2 --eh-frame-hdr -m elf_i386 -dynamic-linker /lib/ld-linux.so.2 -o foo2 /usr/lib/gcc/i686-pc-linux-gnu/3.4.4/../../../crt1.o /usr/lib/gcc/i686-pc-linux-gnu/3.4.4/../../../crti.o /usr/lib/gcc/i686-pc-linux-gnu/3.4.4/crtbegin.o -L/usr/lib/gcc/i686-pc-linux-gnu/3.4.4 -L/usr/lib/gcc/i686-pc-linux-gnu/3.4.4 -L/usr/lib/gcc/i686-pc-linux-gnu/3.4.4/../../../../i686-pc-linux-gnu/lib -L/usr/lib/gcc/i686-pc-linux-gnu/3.4.4/../../.. /tmp/ccokr9zW.o -lgcc -lgcc_eh -lc -lgcc -lgcc_eh /usr/lib/gcc/i686-pc-linux-gnu/3.4.4/crtend.o /usr/lib/gcc/i686-pc-linux-gnu/3.4.4/../../../crtn.o I suspect that the alias analysis use an incorrect size for double.