use setitimer function rather than syscall to implement alarm

otherwise alarm will break on 32-bit archs when time_t is changed to
64-bit. a second itimerval object is introduced for retrieving the old
value, since the setitimer function has restrict-qualified arguments.

diff --git a/src/unistd/alarm.c b/src/unistd/alarm.c
index 2e3263a..a5e0c82 100644 (file)
--- a/src/unistd/alarm.c
+++ b/src/unistd/alarm.c
@@ -4,7 +4,7 @@
 
 unsigned alarm(unsigned seconds)
 {
-       struct itimerval it = { .it_value.tv_sec = seconds };
-       __syscall(SYS_setitimer, ITIMER_REAL, &it, &it);
-       return it.it_value.tv_sec + !!it.it_value.tv_usec;
+       struct itimerval it = { .it_value.tv_sec = seconds }, old = { 0 };
+       setitimer(ITIMER_REAL, &it, &old);
+       return old.it_value.tv_sec + !!old.it_value.tv_usec;
 }