include err.h shim

Includes compatible replacements, or uses system err.h if available.

ok beck@ guenther@

configure.ac.tpl

@@ -111,6 +111,8 @@ AC_CHECK_FUNC(funopen, AC_DEFINE(HAVE_FUNOPEN))
 
 AC_CHECK_HEADER(sys/sysctl.h, AC_DEFINE(HAVE_SYS_SYSCTL_H))
 
+AC_CHECK_HEADER(err.h, AC_DEFINE(HAVE_ERR_H))
+
 AC_ARG_WITH([openssldir],
 	AS_HELP_STRING([--with-openssldir], [Set the default openssl directory]),
 	AC_DEFINE_UNQUOTED(OPENSSLDIR, "$withval")

include/Makefile.am

@@ -1,6 +1,7 @@
 SUBDIRS = openssl
 
-noinst_HEADERS = pqueue.h
+noinst_HEADERS = err.h
+noinst_HEADERS += pqueue.h
 noinst_HEADERS += stdlib.h
 noinst_HEADERS += string.h
 noinst_HEADERS += unistd.h

include/err.h

@@ -0,0 +1,24 @@
+#ifdef HAVE_ERR_H
+
+#include_next <err.h>
+
+#else
+
+#ifndef LIBCRYPTOCOMPAT_ERR_H
+#define LIBCRYPTOCOMPAT_ERR_H
+
+#define err(exitcode, format, args...) \
+  errx(exitcode, format ": %s", ## args, strerror(errno))
+
+#define errx(exitcode, format, args...) \
+  do { warnx(format, ## args); exit(exitcode); } while (0)
+
+#define warn(format, args...) \
+  warnx(format ": %s", ## args, strerror(errno))
+
+#define warnx(format, args...) \
+  fprintf(stderr, format "\n", ## args)
+
+#endif
+
+#endif