aarch64-alt-linux-gcc-10 from gcc10-10.2.1-alt2.aarch64 miscompiles the following innocent example (a simplification of strace/src/print_dev_t.c): $ cat arm64.c #define _GNU_SOURCE #include <assert.h> #include <stdio.h> #include <stdlib.h> #include <sys/sysmacros.h> int main(int ac, const char **av) { assert(ac == 2); const unsigned long long dev = strtoull(av[1], 0, 0); const unsigned long dev_major = major(dev); printf("%#lx\n", dev_major); const unsigned long dev_minor = minor(dev); printf("%#lx\n", dev_minor); return 0; } $ aarch64-alt-linux-gcc-10 -Wall -Werror -O2 arm64.c $ ./a.out 0x123456789abcdef0 0x12345cde 0x123456789abf0 Also reproducible with "gcc (GCC) 10.2.1 20201125 (Red Hat 10.2.1-9)" from f33, apparently fixed in "gcc (GCC) 11.0.0 20210210 (Red Hat 11.0.0-0)" from f34.
Further simplified example: $ cat a.c #include <stdio.h> int main(void) { const unsigned long in = (unsigned long) main; unsigned int val = (in & 0xffU) | ((in >> 8) & 0xffffff00U); printf("%#lx %#lx\n", in, (unsigned long) val); return 0; } $ gcc -Wall -Werror a.c && ./a.out 0xaaaab463d794 0xaab46394 $ gcc -Wall -Werror -O1 a.c && ./a.out 0xaaaabd4cb794 0xaaaabd4c94 $ gcc -Wall -Werror -O2 a.c && ./a.out 0xaaaace920680 0xaaaace9280
The last example: $ cat a.c __attribute__((noipa)) unsigned long f(unsigned long x) { return (unsigned int) ((x & 0xffU) | ((x >> 8) & 0xffffff00U)); } int main(void) { unsigned long v = f(-1UL); if (v != (unsigned int) v) __builtin_abort(); return 0; } $ for i in 0 1 s 2; do printf '%s ' "-O$i" && gcc -Wall -Werror -O$i a.c && ./a.out && echo OK; done -O0 OK -O1 Aborted -Os Aborted -O2 Aborted
gcc10-10.2.1-alt3 -> sisyphus: Mon Mar 15 2021 Gleb F-Malinovskiy <glebfm@altlinux> 10.2.1-alt3 - Updated to merged branches from git://gcc.gnu.org/git/gcc.git (ALT#39798): + vendors/redhat/heads/gcc-10-branch commit 966e4575ccd8b618811b4871e44c31bb2d11a82a; + origin/releases/gcc-10 commit a07015ad4dc18a1167720aece205deca702a1ab1. - gcc10-plugin-devel: added R: libgmp-devel.
