Added function crash_prog() to userland/libc

userland/include/err.h

@@ -55,4 +55,6 @@ void vwarnx(const char *fmt, __va_list);
 __DEAD void verr(int exitcode, const char *fmt, __va_list);
 __DEAD void verrx(int exitcode, const char *fmt, __va_list);
 
+void crash_prog(void);
+
 #endif /* _ERR_H_ */

userland/lib/libc/unix/err.c

@@ -139,6 +139,8 @@ verr(int exitcode, const char *fmt, va_list ap)
 {
 	__printerr(1, fmt, ap);
 	exit(exitcode);
+	// exit() didn't work.
+	crash_prog();
 }
 
 /* errx/verrx: don't use errno, but do then exit */
@@ -147,6 +149,8 @@ verrx(int exitcode, const char *fmt, va_list ap)
 {
 	__printerr(0, fmt, ap);
 	exit(exitcode);
+	// exit() didn't work.
+	crash_prog();
 }
 
 /*
@@ -189,3 +193,12 @@ errx(int exitcode, const char *fmt, ...)
 	verrx(exitcode, fmt, ap);
 	va_end(ap);
 }
+
+void
+crash_prog(void)
+{
+	// Guru: Since exit() may not yet be implemented, just trigger a
+	// failure so things don't fall through to a success print
+	nprintf("Accessing invalid memory location to trigger failure\n");
+	tprintf("%d", *((int *) 0xd34db33f));
+}