[uclibc-ng-devel] [PATCH 2/2] Fix compilation error on noMMU/nothread systems with old compilers

For instance with buildroot config sipeed_maix_bit_defconfig the pre-processor generates if (1) r = ({ long _sys_result; { register long int _a7 __asm__ ("a7"); register long _a3 __asm__ ("a3"); long _a3tmp; register long _a2 __asm__ ("a2"); long _a2tmp; register long _a1 __asm__ ("a1"); long _a1tmp; long _a0tmp; register long _a0 __asm__ ("a0"); _a0tmp = (long) (clock_id); _a0 = _a0tmp; _a1tmp = (long) (flags); _a1 = _a1tmp; _a2tmp = (long) (req); _a2 = _a2tmp; _a3tmp = (long) (rem); _a3 = _a3tmp; _a7 = (115); __asm__ volatile ( "scall\n\t" : "=r" (_a0) : "r"(_a7) , "r" (_a0), "r" (_a1), "r" (_a2), "r" (_a3) : "memory"); _sys_result = _a0; } _sys_result; }); else { int oldstate = LIBC_CANCEL_ASYNC (); r = ({ long _sys_result; { register long int _a7 __asm__ ("a7"); register long _a3 __asm__ ("a3"); long _a3tmp; register long _a2 __asm__ ("a2"); long _a2tmp; register long _a1 __asm__ ("a1"); long _a1tmp; long _a0tmp; register long _a0 __asm__ ("a0"); _a0tmp = (long) (clock_id); _a0 = _a0tmp; _a1tmp = (long) (flags); _a1 = _a1tmp; _a2tmp = (long) (req); _a2 = _a2tmp; _a3tmp = (long) (rem); _a3 = _a3tmp; _a7 = (115); __asm__ volatile ( "scall\n\t" : "=r" (_a0) : "r"(_a7) , "r" (_a0), "r" (_a1), "r" (_a2), "r" (_a3) : "memory"); _sys_result = _a0; } _sys_result; }) ; LIBC_CANCEL_RESET (oldstate); } And also the compiler issues these warnings: librt/clock_nanosleep.c: In function 'clock_nanosleep': librt/clock_nanosleep.c:43:22: warning: implicit declaration of function 'LIBC_CANCEL_ASYNC'; did you mean 'LIBC_CANCEL_HANDLED'? [-Wimplicit-function-declaration] 43 | int oldstate = LIBC_CANCEL_ASYNC (); | ^~~~~~~~~~~~~~~~~ | LIBC_CANCEL_HANDLED librt/clock_nanosleep.c:48:7: warning: implicit declaration of function 'LIBC_CANCEL_RESET'; did you mean 'LIBC_CANCEL_HANDLED'? [-Wimplicit-function-declaration] 48 | LIBC_CANCEL_RESET (oldstate); | ^~~~~~~~~~~~~~~~~ | LIBC_CANCEL_HANDLED So if the compiler is a bit picky and does not optimize the if (1) {} else {} it can fail to link with undefined symbols. This patch fixes this issue: no more warning. Btw, that's the solution that is already used in the following cancellation point files: * libc/sysdeps/linux/common/__syscall_fcntl.c * libc/sysdeps/linux/common/__syscall_fcntl64.c * libc/sysdeps/linux/common/ioctl.c * libc/sysdeps/linux/common/openat.c * libc/sysdeps/linux/common/open.c Signed-off-by: Yann Sionneau <yann(a)sionneau.net> --- librt/clock_nanosleep.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/librt/clock_nanosleep.c b/librt/clock_nanosleep.c index 4cf1e06b4..85db72fb3 100644 --- a/librt/clock_nanosleep.c +++ b/librt/clock_nanosleep.c @@ -40,12 +40,14 @@ clock_nanosleep (clockid_t clock_id, int flags, const struct timespec *req, r = INTERNAL_SYSCALL (clock_nanosleep, err, 4, clock_id, flags, req, rem); else { +#ifdef __NEW_THREADS int oldstate = LIBC_CANCEL_ASYNC (); r = INTERNAL_SYSCALL (clock_nanosleep, err, 4, clock_id, flags, req, rem); LIBC_CANCEL_RESET (oldstate); +#endif } return (INTERNAL_SYSCALL_ERROR_P (r, err) -- 2.34.1