libroot: system() should ignore SIGINT, SIGQUIT while waiting

https://pubs.opengroup.org/onlinepubs/9699919799/functions/system.html
Change-Id: Ic9919e403fb4e6ee4406b0c33789fe8b00b22d1f
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5341
Reviewed-by: waddlesplash <[email protected]>
Tested-by: Commit checker robot <[email protected]>

src/system/libroot/posix/unistd/system.cpp

@@ -8,6 +8,7 @@
 #include <errno.h>
 #include <pthread.h>
 #include <stdlib.h>
+#include <string.h>
 #include <sys/wait.h>
 #include <unistd.h>
 
@@ -28,6 +29,20 @@ system(const char *command)
 	if (thread < 0)
 		RETURN_AND_SET_ERRNO_TEST_CANCEL(thread);
 
+	// block SIGCHLD ...
+	sigset_t mask, oldMask;
+	sigemptyset(&mask);
+	sigaddset(&mask, SIGCHLD);
+	sigprocmask(SIG_BLOCK, &mask, &oldMask);
+
+	// and ignore SIGINT and SIGQUIT while waiting for completion
+	struct sigaction intSave, quitSave, sa;
+	memset(&sa, 0, sizeof(sa));
+	sigemptyset(&sa.sa_mask);
+	sa.sa_handler = SIG_IGN;
+	sigaction(SIGINT, &sa, &intSave);
+	sigaction(SIGQUIT, &sa, &quitSave);
+
 	resume_thread(thread);
 
 	int exitStatus;
@@ -37,6 +52,11 @@ system(const char *command)
 		// waitpid() was interrupted by a signal, retry...
 	}
 
+	// unblock and reset signal handlers
+	sigprocmask(SIG_SETMASK, &oldMask, NULL);
+	sigaction(SIGINT, &intSave, NULL);
+	sigaction(SIGQUIT, &quitSave, NULL);
+
 	if (result < 0)
 		return -1;