Use sigaction(2) instead of sigignore(3) for portability

sigignore(3) isn't portable.
This code fails to compile on platforms without sigignore(3).
Use sigaction(2).

--
zfs_main.c: In function 'zfs_do_diff':
zfs_main.c:7178:9: error: implicit declaration of function 'sigignore' [-Werror=implicit-function-declaration]
  (void) sigignore(SIGPIPE);
         ^~~~~~~~~

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Tomohiro Kusumi <[email protected]>
Closes #8593

1 files changed, 12 insertions, 2 deletions

diff --git a/cmd/zfs/zfs_main.c b/cmd/zfs/zfs_main.c
index 90893a857..2d97988a0 100644
--- a/cmd/zfs/zfs_main.c
+++ b/cmd/zfs/zfs_main.c
@@ -7195,6 +7195,7 @@ zfs_do_diff(int argc, char **argv)
 	char *atp, *copy;
 	int err = 0;
 	int c;
+	struct sigaction sa;
 
 	while ((c = getopt(argc, argv, "FHt")) != -1) {
 		switch (c) {
@@ -7252,10 +7253,19 @@ zfs_do_diff(int argc, char **argv)
 	 * Ignore SIGPIPE so that the library can give us
 	 * information on any failure
 	 */
-	(void) sigignore(SIGPIPE);
+	if (sigemptyset(&sa.sa_mask) == -1) {
+		err = errno;
+		goto out;
+	}
+	sa.sa_flags = 0;
+	sa.sa_handler = SIG_IGN;
+	if (sigaction(SIGPIPE, &sa, NULL) == -1) {
+		err = errno;
+		goto out;
+	}
 
 	err = zfs_show_diffs(zhp, STDOUT_FILENO, fromsnap, tosnap, flags);
-
+out:
 	zfs_close(zhp);
 
 	return (err != 0);