make xfunctions optionally longjump instead of exit.

use it for making NOFORK more practical.
touch: make it a NOFORK applet

applets/applets.c

@@ -462,7 +462,7 @@ void bb_show_usage(void)
 					applet_name, usage_string);
 	}
 
-	exit(xfunc_error_retval);
+	sleep_and_die();
 }
 
 

coreutils/cmp.c

@@ -30,7 +30,7 @@ static FILE *cmp_xfopen_input(const char * const filename)
 	fp = fopen_or_warn_stdin(filename);
 	if (fp)
 		return fp;
-	exit(xfunc_error_retval);	/* We already output an error message. */
+	sleep_and_die();	/* We already output an error message. */
 }
 
 static const char fmt_eof[] = "cmp: EOF on %s\n";

coreutils/touch.c

@@ -17,21 +17,16 @@
  * Also, exiting on a failure was a bug.  All args should be processed.
  */
 
-#include <stdio.h>
-#include <sys/types.h>
-#include <fcntl.h>
-#include <utime.h>
-#include <errno.h>
-#include <unistd.h>
-#include <stdlib.h>
 #include "busybox.h"
 
+/* This is a NOFORK applet. Be very careful! */
+
 int touch_main(int argc, char **argv);
 int touch_main(int argc, char **argv)
 {
 	int fd;
 	int status = EXIT_SUCCESS;
-	bool flags = (getopt32(argc, argv, "c") & 1);
+	int flags = getopt32(argc, argv, "c");
 
 	argv += optind;
 
@@ -41,7 +36,7 @@ int touch_main(int argc, char **argv)
 
 	do {
 		if (utime(*argv, NULL)) {
-			if (errno == ENOENT) {	/* no such file*/
+			if (errno == ENOENT) {	/* no such file */
 				if (flags) {	/* Creation is disabled, so ignore. */
 					continue;
 				}

include/applets.h

@@ -319,7 +319,7 @@ USE_TFTP(APPLET(tftp, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
 #endif
 USE_TIME(APPLET(time, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
 USE_TOP(APPLET(top, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
-USE_TOUCH(APPLET_NOEXEC(touch, touch, _BB_DIR_BIN, _BB_SUID_NEVER, touch))
+USE_TOUCH(APPLET_NOFORK(touch, touch, _BB_DIR_BIN, _BB_SUID_NEVER, touch))
 USE_TR(APPLET(tr, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
 USE_TRACEROUTE(APPLET(traceroute, _BB_DIR_USR_BIN, _BB_SUID_MAYBE))
 USE_TRUE(APPLET(true, _BB_DIR_BIN, _BB_SUID_NEVER))

include/libbb.h

@@ -620,6 +620,7 @@ extern const char *msg_eol;
 extern smallint logmode;
 extern int die_sleep;
 extern int xfunc_error_retval;
+extern jmp_buf die_jmp;
 extern void sleep_and_die(void) ATTRIBUTE_NORETURN;
 extern void bb_show_usage(void) ATTRIBUTE_NORETURN ATTRIBUTE_EXTERNALLY_VISIBLE;
 extern void bb_error_msg(const char *s, ...) __attribute__ ((format (printf, 1, 2)));

libbb/copyfd.c

@@ -77,7 +77,7 @@ void complain_copyfd_and_die(off_t sz)
 	if (sz != -1)
 		bb_error_msg_and_die("short read");
 	/* if sz == -1, bb_copyfd_XX already complained */
-	exit(xfunc_error_retval);
+	sleep_and_die();
 }
 #endif
 
@@ -97,7 +97,7 @@ void bb_copyfd_exact_size(int fd1, int fd2, off_t size)
 	if (sz != -1)
 		bb_error_msg_and_die("short read");
 	/* if sz == -1, bb_copyfd_XX already complained */
-	exit(xfunc_error_retval);
+	sleep_and_die();
 }
 
 off_t bb_copyfd_eof(int fd1, int fd2)

libbb/error_msg_and_die.c

@@ -7,18 +7,19 @@
  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  */
 
-#include <stdio.h>
-#include <errno.h>
-#include <string.h>
-#include <stdlib.h>
 #include "libbb.h"
 
 int die_sleep;
+jmp_buf die_jmp;
 
 void sleep_and_die(void)
 {
-	if (die_sleep)
+	if (die_sleep) {
+		/* Special case: don't die, but jump */
+		if (die_sleep < 0)
+			longjmp(die_jmp, xfunc_error_retval);
 		sleep(die_sleep);
+	}
 	exit(xfunc_error_retval);
 }
 

libbb/getopt32.c

@@ -457,6 +457,7 @@ getopt32(int argc, char **argv, const char *applet_opts, ...)
 
 	/* In case getopt32 was already called, reinit some state */
 	optind = 1;
+	/* optarg = NULL; opterr = 0; optopt = 0; ?? */
 
 	/* Note: just "getopt() <= 0" will not work good for
 	 * "fake" short options, like this one:

libbb/vfork_daemon_rexec.c

@@ -115,11 +115,27 @@ int spawn_and_wait(char **argv)
 			char **pp = argv;
 			while (*++pp)
 				argc++;
-#ifdef BB_NOMMU
-			return a->main(argc, argv);
-#else
+#ifndef BB_NOMMU
 			if (a->nofork)
-				return a->main(argc, argv);
+#endif
+			{
+				int old_sleep = die_sleep;
+				die_sleep = -1; /* special flag */
+				/* sleep_and_die() checks for it */
+				rc = setjmp(die_jmp);
+				if (!rc) {
+					const struct BB_applet *old_a = current_applet;
+					current_applet = a;
+					applet_name = a->name;
+// what else should we save/restore?
+					rc = a->main(argc, argv);
+					current_applet = old_a;
+					applet_name = old_a->name;					
+				}
+				die_sleep = old_sleep;
+				return rc;
+			}
+#ifndef BB_NOMMU	/* MMU only */
 			/* a->noexec is true */
 			rc = fork();
 			if (rc)
@@ -135,6 +151,7 @@ int spawn_and_wait(char **argv)
 	return wait4pid(rc);
 }
 
+
 #if 0 //ndef BB_NOMMU
 // Die with an error message if we can't daemonize.
 void xdaemon(int nochdir, int noclose)

libbb/xfuncs.c

@@ -476,7 +476,7 @@ void xprint_and_close_file(FILE *file)
 	fflush(stdout);
 	// copyfd outputs error messages for us.
 	if (bb_copyfd_eof(fileno(file), 1) == -1)
-		exit(xfunc_error_retval);
+		sleep_and_die();
 
 	fclose(file);
 }