portability and standards: add BSD-like err() and errx() functions

These are BSD functions.
- HaikuOS now compiles without having to use libbsd.
- Tested on SerenityOS (for fun), which doesn't have these functions (yet).
  With a small change to support wcwidth() sfeed works on SerenityOS.

README

@@ -117,7 +117,8 @@ OS tested
 - FreeBSD
 - DragonFlyBSD
 - Windows (cygwin gcc, mingw).
-- HaikuOS (using libbsd).
+- HaikuOS
+- SerenityOS
 - FreeDOS (djgpp).
 - FUZIX (sdcc -mz80).
 

sfeed.c

@@ -1,7 +1,6 @@
 #include <sys/types.h>
 
 #include <ctype.h>
-#include <err.h>
 #include <errno.h>
 #include <stdint.h>
 #include <stdio.h>

sfeed_atom.c

@@ -1,6 +1,5 @@
 #include <sys/types.h>
 
-#include <err.h>
 #include <stdio.h>
 #include <string.h>
 #include <time.h>

sfeed_frames.c

@@ -1,6 +1,5 @@
 #include <sys/types.h>
 
-#include <err.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>

sfeed_gopher.c

@@ -1,6 +1,5 @@
 #include <sys/types.h>
 
-#include <err.h>
 #include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>

sfeed_html.c

@@ -1,6 +1,5 @@
 #include <sys/types.h>
 
-#include <err.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>

sfeed_mbox.c

@@ -1,4 +1,3 @@
-#include <err.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>

sfeed_opml_import.c

@@ -1,5 +1,4 @@
 #include <ctype.h>
-#include <err.h>
 #include <stdio.h>
 #include <strings.h>
 

sfeed_plain.c

@@ -1,6 +1,5 @@
 #include <sys/types.h>
 
-#include <err.h>
 #include <locale.h>
 #include <stdio.h>
 #include <string.h>

sfeed_twtxt.c

@@ -1,6 +1,5 @@
 #include <sys/types.h>
 
-#include <err.h>
 #include <stdio.h>
 #include <string.h>
 #include <time.h>

sfeed_web.c

@@ -1,5 +1,4 @@
 #include <ctype.h>
-#include <err.h>
 #include <stdio.h>
 #include <strings.h>
 

sfeed_xmlenc.c

@@ -1,5 +1,4 @@
 #include <ctype.h>
-#include <err.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <strings.h>

util.c

@@ -1,5 +1,6 @@
 #include <ctype.h>
 #include <errno.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -7,6 +8,44 @@
 
 #include "util.h"
 
+/* print to stderr, print error message of errno and exit().
+   Unlike BSD err() it does not prefix __progname */
+__dead void
+err(int exitstatus, const char *fmt, ...)
+{
+	va_list ap;
+	int saved_errno;
+
+	saved_errno = errno;
+
+	if (fmt) {
+		va_start(ap, fmt);
+		vfprintf(stderr, fmt, ap);
+		va_end(ap);
+		fprintf(stderr, ": ");
+	}
+	fprintf(stderr, "%s\n", strerror(saved_errno));
+
+	exit(exitstatus);
+}
+
+/* print to stderr and exit().
+   Unlike BSD errx() it does not prefix __progname */
+__dead void
+errx(int exitstatus, const char *fmt, ...)
+{
+	va_list ap;
+
+	if (fmt) {
+		va_start(ap, fmt);
+		vfprintf(stderr, fmt, ap);
+		va_end(ap);
+	}
+	fputs("\n", stderr);
+
+	exit(exitstatus);
+}
+
 /* check if string has a non-empty scheme / protocol part */
 int
 uri_hasscheme(const char *s)

util.h

@@ -38,6 +38,14 @@ enum {
 	FieldLast
 };
 
+/* hint for compilers and static analyzers that a function exits */
+#ifndef __dead
+#define __dead
+#endif
+
+__dead void err(int, const char *, ...);
+__dead void errx(int, const char *, ...);
+
 int uri_format(char *, size_t, struct uri *);
 int uri_hasscheme(const char *);
 int uri_makeabs(struct uri *, struct uri *, struct uri *);