[PATCH 3/5] use `%m' for *printf rather than strerror(errno)

[Eric Wong <e@80x24.org>]

FreeBSD, glibc both support it, as do minimalist libcs such as
uClibc and musl.
---
 mwrap_core.h | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/mwrap_core.h b/mwrap_core.h
index 6d498c1..179f136 100644
--- a/mwrap_core.h
+++ b/mwrap_core.h
@@ -826,8 +826,7 @@ static void dump_destructor(void)
 		dump_fd = open(dump_path, O_CLOEXEC|O_WRONLY|O_APPEND|O_CREAT,
 				0666);
 		if (dump_fd < 0) {
-			fprintf(stderr, "open %s failed: %s\n", dump_path,
-				strerror(errno));
+			fprintf(stderr, "open %s failed: %m\n", dump_path);
 			goto out;
 		}
 	}
@@ -850,8 +849,7 @@ static void dump_destructor(void)
 			a.fp = fdopen(dump_fd, modes[i]);
 
 		if (!a.fp) {
-			fprintf(stderr, "failed to open fd=%d: %s\n",
-				dump_fd, strerror(errno));
+			fprintf(stderr, "failed to open fd=%d: %m\n", dump_fd);
 			goto out;
 		}
 		/* we'll leak some memory here, but this is a destructor */
@@ -948,7 +946,7 @@ __attribute__((constructor)) static void mwrap_ctor(void)
 		h->real = h;
 		call_rcu(&h->as.dead, free_hdr_rcu);
 	} else
-		fprintf(stderr, "malloc failed: %s\n", strerror(errno));
+		fprintf(stderr, "malloc: %m\n");
 
 	h1d_start();
 	CHECK(int, 0, pthread_sigmask(SIG_SETMASK, &old, NULL));