Mark errf _Noreturn, and mark errf and warn __printflike

The _Noreturn attribute was added to placate Coverity and other static
analysis tools. The __printflike attribute was added to catch issues
with the calls related to printf(3) abuse.

- Modify the code to facilitate the __printflike attribute addition.
- Convert errf calls in to_mb(..) and to_mb_string(..) to warn(..) so
  the calls will return instead of exiting, as the code suggests it
  should.

Differential Revision:	D10704
MFC after:	1 month
Reviewed by:	pfg
Sponsored by:	Dell EMC Isilon

usr.bin/localedef/localedef.c

@@ -119,7 +119,7 @@ open_category(void)
 	 */
 	file = fopen(category_file(), "w");
 	if (file == NULL) {
-		errf(strerror(errno));
+		errf("%s", strerror(errno));
 		return (NULL);
 	}
 	return (file);
@@ -131,11 +131,11 @@ close_category(FILE *f)
 	if (fchmod(fileno(f), 0644) < 0) {
 		(void) fclose(f);
 		(void) unlink(category_file());
-		errf(strerror(errno));
+		errf("%s", strerror(errno));
 	}
 	if (fclose(f) < 0) {
 		(void) unlink(category_file());
-		errf(strerror(errno));
+		errf("%s", strerror(errno));
 	}
 	if (verbose) {
 		(void) fprintf(stdout, "done.\n");
@@ -195,13 +195,13 @@ putl_category(const char *s, FILE *f)
 	if (s && fputs(s, f) == EOF) {
 		(void) fclose(f);
 		(void) unlink(category_file());
-		errf(strerror(errno));
+		errf("%s", strerror(errno));
 		return (EOF);
 	}
 	if (fputc('\n', f) == EOF) {
 		(void) fclose(f);
 		(void) unlink(category_file());
-		errf(strerror(errno));
+		errf("%s", strerror(errno));
 		return (EOF);
 	}
 	return (0);
@@ -216,7 +216,7 @@ wr_category(void *buf, size_t sz, FILE *f)
 	if (fwrite(buf, sz, 1, f) < 1) {
 		(void) fclose(f);
 		(void) unlink(category_file());
-		errf(strerror(errno));
+		errf("%s", strerror(errno));
 		return (EOF);
 	}
 	return (0);
@@ -331,7 +331,7 @@ main(int argc, char **argv)
 		while ((dir = opendir(locname)) == NULL) {
 			if ((errno != ENOENT) ||
 			    (mkdir(locname, 0755) <  0)) {
-				errf(strerror(errno));
+				errf("%s", strerror(errno));
 			}
 		}
 		(void) closedir(dir);

usr.bin/localedef/localedef.h

@@ -35,6 +35,7 @@
  */
 
 /* Common header files. */
+#include <sys/cdefs.h>
 #include <sys/types.h>
 #include <stdarg.h>
 #include <stdio.h>
@@ -54,8 +55,8 @@ extern int warnings;
 
 int yylex(void);
 void yyerror(const char *);
-void errf(const char *, ...);
-void warn(const char *, ...);
+_Noreturn void errf(const char *, ...) __printflike(1, 2);
+void warn(const char *, ...) __printflike(1, 2);
 
 int putl_category(const char *, FILE *);
 int wr_category(void *, size_t, FILE *);

usr.bin/localedef/wide.c

@@ -598,7 +598,7 @@ to_mb(char *mb, wchar_t wc)
 	int	rv;
 
 	if ((rv = _tomb(mb, wc)) < 0) {
-		errf(widemsg);
+		warn("%s", widemsg);
 		free(widemsg);
 		widemsg = NULL;
 	}
@@ -614,7 +614,7 @@ to_mb_string(const wchar_t *wcs)
 
 	mbs = malloc((wcslen(wcs) * mb_cur_max) + 1);
 	if (mbs == NULL) {
-		errf("out of memory");
+		warn("out of memory");
 		return (NULL);
 	}
 	ptr = mbs;