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 <[email protected]>
---
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
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