use %m printf specifier where appropriate

function                                             old     new   delta
out                                                   85      75     -10
udhcpd_main                                         1472    1461     -11
open_stdio_to_tty                                     98      85     -13
init_exec                                            245     232     -13
udhcpc_main                                         2763    2749     -14
do_cmd                                              4771    4755     -16
status_line_bold_errno                                32      14     -18
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/7 up/down: 0/-95)             Total: -95 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

editors/vi.c

@@ -1038,7 +1038,7 @@ static void colon(char *buf)
 		}
 		if (cnt < 0) {
 			if (cnt == -1)
-				status_line_bold("Write error: %s", strerror(errno));
+				status_line_bold("Write error: "STRERROR_FMT STRERROR_ERRNO);
 		} else {
 			modified_count = 0;
 			last_modified_count = -1;
@@ -3131,7 +3131,7 @@ static void status_line_bold(const char *format, ...)
 
 static void status_line_bold_errno(const char *fn)
 {
-	status_line_bold("'%s' %s", fn, strerror(errno));
+	status_line_bold("'%s' "STRERROR_FMT, fn STRERROR_ERRNO);
 }
 
 // format status buffer
@@ -4066,7 +4066,7 @@ static void do_cmd(int c)
 			cnt = file_write(current_filename, text, end - 1);
 			if (cnt < 0) {
 				if (cnt == -1)
-					status_line_bold("Write error: %s", strerror(errno));
+					status_line_bold("Write error: "STRERROR_FMT STRERROR_ERRNO);
 			} else if (cnt == (end - 1 - text + 1)) {
 				editing = 0;
 			}

include/libbb.h

@@ -162,6 +162,17 @@
 #ifndef HAVE_XTABS
 # define XTABS TAB3
 #endif
+/*
+ * Use '%m' to append error string on platforms that support it,
+ * '%s' and strerror() on those that don't.
+ */
+#ifdef HAVE_PRINTF_PERCENTM
+# define STRERROR_FMT    "%m"
+# define STRERROR_ERRNO  /*nothing*/
+#else
+# define STRERROR_FMT    "%s"
+# define STRERROR_ERRNO  ,strerror(errno)
+#endif
 
 
 /* Some libc's forget to declare these, do it ourself */

init/init.c

@@ -391,8 +391,10 @@ static int open_stdio_to_tty(const char* tty_name)
 		/* fd can be only < 0 or 0: */
 		fd = device_open(tty_name, O_RDWR);
 		if (fd) {
-			message(L_LOG | L_CONSOLE, "can't open %s: %s",
-				tty_name, strerror(errno));
+			message(L_LOG | L_CONSOLE, "can't open %s: "STRERROR_FMT,
+				tty_name
+				STRERROR_ERRNO
+			);
 			return 0; /* failure */
 		}
 		dup2(STDIN_FILENO, STDOUT_FILENO);
@@ -469,7 +471,7 @@ static void init_exec(const char *command)
 	}
 	/* Here command never contains the dash, cmd[0] might */
 	BB_EXECVP(command, cmd);
-	message(L_LOG | L_CONSOLE, "can't run '%s': %s", command, strerror(errno));
+	message(L_LOG | L_CONSOLE, "can't run '%s': "STRERROR_FMT, command STRERROR_ERRNO);
 	/* returns if execvp fails */
 }
 

networking/udhcp/d6_dhcpc.c

@@ -1432,7 +1432,7 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
 				len = d6_recv_raw_packet(&srv6_buf, &packet, sockfd);
 			if (len == -1) {
 				/* Error is severe, reopen socket */
-				bb_error_msg("read error: %s, reopening socket", strerror(errno));
+				bb_error_msg("read error: "STRERROR_FMT", reopening socket" STRERROR_ERRNO);
 				sleep(discover_timeout); /* 3 seconds by default */
 				change_listen_mode(listen_mode); /* just close and reopen */
 			}

networking/udhcp/dhcpc.c

@@ -1631,7 +1631,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 				len = udhcp_recv_raw_packet(&packet, sockfd);
 			if (len == -1) {
 				/* Error is severe, reopen socket */
-				bb_error_msg("read error: %s, reopening socket", strerror(errno));
+				bb_error_msg("read error: "STRERROR_FMT", reopening socket" STRERROR_ERRNO);
 				sleep(discover_timeout); /* 3 seconds by default */
 				change_listen_mode(listen_mode); /* just close and reopen */
 			}

networking/udhcp/dhcpd.c

@@ -948,7 +948,7 @@ int udhcpd_main(int argc UNUSED_PARAM, char **argv)
 		if (bytes < 0) {
 			/* bytes can also be -2 ("bad packet data") */
 			if (bytes == -1 && errno != EINTR) {
-				log1("read error: %s, reopening socket", strerror(errno));
+				log1("read error: "STRERROR_FMT", reopening socket" STRERROR_ERRNO);
 				close(server_socket);
 				server_socket = -1;
 			}

runit/sv.c

@@ -224,7 +224,7 @@ static void out(const char *p, const char *m1)
 {
 	printf("%s%s%s: %s", p, *service, islog ? "/log" : "", m1);
 	if (errno) {
-		printf(": %s", strerror(errno));
+		printf(": "STRERROR_FMT STRERROR_ERRNO);
 	}
 	bb_putchar('\n'); /* will also flush the output */
 }

selinux/matchpathcon.c

@@ -104,7 +104,7 @@ int matchpathcon_main(int argc UNUSED_PARAM, char **argv)
 			freecon(con);
 			continue;
 		}
-		printf("actual context unknown: %s, should be ", strerror(errno));
+		printf("actual context unknown: "STRERROR_FMT", should be " STRERROR_ERRNO);
 		error += print_matchpathcon(path, 1);
 	}
 	matchpathcon_fini();

shell/ash.c

@@ -1312,16 +1312,9 @@ ash_msg_and_raise_error(const char *msg, ...)
 }
 
 /*
- * Use '%m' to append error string on platforms that support it, '%s' and
- * strerror() on those that don't.
- *
  * 'fmt' must be a string literal.
  */
-#ifdef HAVE_PRINTF_PERCENTM
-#define ash_msg_and_raise_perror(fmt, ...) ash_msg_and_raise_error(fmt ": %m", ##__VA_ARGS__)
-#else
-#define ash_msg_and_raise_perror(fmt, ...) ash_msg_and_raise_error(fmt ": %s", ##__VA_ARGS__, strerror(errno))
-#endif
+#define ash_msg_and_raise_perror(fmt, ...) ash_msg_and_raise_error(fmt ": "STRERROR_FMT, ##__VA_ARGS__ STRERROR_ERRNO)
 
 static void raise_error_syntax(const char *) NORETURN;
 static void