conf: flush stdout before early exit

Before doing an early exit any contents of stdout is normally flushed.
This doesn't happen when the output goes into a pipe and we return with
_exit(). We now add an explicit flush in such cases.

Reported-by: John Radley <jradxl2@gmail.com>
Fixes: d0006fa784a7 ("treewide: use _exit() over exit()")
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
Reviewed-by: Paul Holzinger <pholzing@redhat.com>
[sbrivio: cast fflush() calls to void to dodge clang-tidy warning]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/conf.c b/conf.c
index f4c8ca2..36845e2 100644
--- a/conf.c
+++ b/conf.c
@@ -975,6 +975,7 @@ static void usage(const char *name, FILE *f, int status)
 		"    SPEC is as described for TCP above\n"
 		"    default: none\n");
 
+	(void)fflush(f);
 	_exit(status);
 
 pasta_opts:
@@ -1029,6 +1030,7 @@ pasta_opts:
 		"  --ns-mac-addr ADDR	Set MAC address on tap interface\n"
 		"  --no-splice		Disable inbound socket splicing\n");
 
+	(void)fflush(f);
 	_exit(status);
 }
 
@@ -1594,6 +1596,7 @@ void conf(struct ctx *c, int argc, char **argv)
 			FPRINTF(stdout,
 				c->mode == MODE_PASTA ? "pasta " : "passt ");
 			FPRINTF(stdout, VERSION_BLOB);
+			(void)fflush(stdout);
 			_exit(EXIT_SUCCESS);
 		case 15:
 			ret = snprintf(c->ip4.ifname_out,