ash: better fix for ash -c 'echo 5&' and ash -c 'sleep 5&'

with testcase

shell/ash.c

@@ -9079,8 +9079,6 @@ breakcmd(int argc UNUSED_PARAM, char **argv)
  * This implements the input routines used by the parser.
  */
 
-#define EOF_NLEFT -99           /* value of parsenleft when EOF pushed back */
-
 enum {
 	INPUT_PUSH_FILE = 1,
 	INPUT_NOFILE_OK = 2,
@@ -9121,7 +9119,6 @@ popstring(void)
 #endif
 	parsenextc = sp->prevstring;
 	parsenleft = sp->prevnleft;
-/*dprintf("*** calling popstring: restoring to '%s'\n", parsenextc);*/
 	g_parsefile->strpush = sp->prev;
 	if (sp != &(g_parsefile->basestrpush))
 		free(sp);
@@ -9137,7 +9134,7 @@ preadfd(void)
 
 #if ENABLE_FEATURE_EDITING
  retry:
-	if (!iflag || g_parsefile->fd)
+	if (!iflag || g_parsefile->fd != STDIN_FILENO)
 		nr = nonblock_safe_read(g_parsefile->fd, buf, BUFSIZ - 1);
 	else {
 #if ENABLE_FEATURE_TAB_COMPLETION
@@ -9185,56 +9182,76 @@ preadfd(void)
  * Refill the input buffer and return the next input character:
  *
  * 1) If a string was pushed back on the input, pop it;
- * 2) If an EOF was pushed back (parsenleft == EOF_NLEFT) or we are reading
+ * 2) If an EOF was pushed back (parsenleft < -BIGNUM) or we are reading
  *    from a string so we can't refill the buffer, return EOF.
  * 3) If the is more stuff in this buffer, use it else call read to fill it.
  * 4) Process input up to the next newline, deleting nul characters.
  */
+//#define pgetc_debug(...) bb_error_msg(__VA_ARGS__)
+#define pgetc_debug(...) ((void)0)
 static int
 preadbuffer(void)
 {
 	char *q;
 	int more;
-	char savec;
 
 	while (g_parsefile->strpush) {
 #if ENABLE_ASH_ALIAS
 		if (parsenleft == -1 && g_parsefile->strpush->ap
 		 && parsenextc[-1] != ' ' && parsenextc[-1] != '\t'
 		) {
+			pgetc_debug("preadbuffer PEOA");
 			return PEOA;
 		}
 #endif
 		popstring();
+		/* try "pgetc" now: */
+		pgetc_debug("internal pgetc at %d:%p'%s'", parsenleft, parsenextc, parsenextc);
 		if (--parsenleft >= 0)
 			return signed_char2int(*parsenextc++);
 	}
-	if (parsenleft == EOF_NLEFT || g_parsefile->buf == NULL)
+	/* on both branches above parsenleft < 0.
+	 * "pgetc" needs refilling.
+	 */
+
+	/* -90 is -BIGNUM. Below we use -99 to mark "EOF on read",
+	 * pungetc() may decrement it a few times. -90 is enough.
+	 */
+	if (parsenleft < -90 || g_parsefile->buf == NULL) {
+		pgetc_debug("preadbuffer PEOF1");
+		/* even in failure keep them in lock step,
+		 * for correct pungetc. */
+		parsenextc++;
 		return PEOF;
-	flush_stdout_stderr();
+	}
 
 	more = parselleft;
 	if (more <= 0) {
+		flush_stdout_stderr();
  again:
 		more = preadfd();
 		if (more <= 0) {
-			parselleft = parsenleft = EOF_NLEFT;
+			parselleft = parsenleft = -99;
+			pgetc_debug("preadbuffer PEOF2");
+			parsenextc++;
 			return PEOF;
 		}
 	}
 
+	/* Find out where's the end of line.
+	 * Set parsenleft/parselleft acordingly.
+	 * NUL chars are deleted.
+	 */
 	q = parsenextc;
-
-	/* delete nul characters */
 	for (;;) {
-		int c;
+		char c;
 
 		more--;
-		c = *q;
 
-		if (!c)
+		c = *q;
+		if (c == '\0') {
 			memmove(q, q + 1, more);
-		else {
+		} else {
 			q++;
 			if (c == '\n') {
 				parsenleft = q - parsenextc - 1;
@@ -9251,22 +9268,23 @@ preadbuffer(void)
 	}
 	parselleft = more;
 
-	savec = *q;
-	*q = '\0';
-
 	if (vflag) {
+		char save = *q;
+		*q = '\0';
 		out2str(parsenextc);
+		*q = save;
 	}
 
-	*q = savec;
-
+	pgetc_debug("preadbuffer at %d:%p'%s'", parsenleft, parsenextc, parsenextc);
 	return signed_char2int(*parsenextc++);
 }
 
 #define pgetc_as_macro() (--parsenleft >= 0 ? signed_char2int(*parsenextc++) : preadbuffer())
+
 static int
 pgetc(void)
 {
+	pgetc_debug("pgetc at %d:%p'%s'", parsenleft, parsenextc, parsenextc);
 	return pgetc_as_macro();
 }
 
@@ -9325,11 +9343,9 @@ pfgets(char *line, int len)
 static void
 pungetc(void)
 {
-	/* check is needed for ash -c 'echo 5&' + BASH_COMPAT to work */
-	if (parsenleft < 0)
-		return;
 	parsenleft++;
 	parsenextc--;
+	pgetc_debug("pushed back to %d:%p'%s'", parsenleft, parsenextc, parsenextc);
 }
 
 /*
@@ -9343,16 +9359,17 @@ static void
 pushstring(char *s, struct alias *ap)
 {
 	struct strpush *sp;
-	size_t len;
+	int len;
 
 	len = strlen(s);
 	INT_OFF;
 	if (g_parsefile->strpush) {
-		sp = ckzalloc(sizeof(struct strpush));
+		sp = ckzalloc(sizeof(*sp));
 		sp->prev = g_parsefile->strpush;
-		g_parsefile->strpush = sp;
-	} else
-		sp = g_parsefile->strpush = &(g_parsefile->basestrpush);
+	} else {
+		sp = &(g_parsefile->basestrpush);
+	}
+	g_parsefile->strpush = sp;
 	sp->prevstring = parsenextc;
 	sp->prevnleft = parsenleft;
 #if ENABLE_ASH_ALIAS
@@ -9442,7 +9459,7 @@ setinputfd(int fd, int push)
 	close_on_exec_on(fd);
 	if (push) {
 		pushfile();
-		g_parsefile->buf = 0;
+		g_parsefile->buf = NULL;
 	}
 	g_parsefile->fd = fd;
 	if (g_parsefile->buf == NULL)

shell/ash_test/ash-misc/last_amp.right

@@ -0,0 +1,2 @@
+3
+End

shell/ash_test/ash-misc/last_amp.tests

@@ -0,0 +1,8 @@
+$THIS_SH -c 'echo 3&'
+d=`date`
+while test "`date`" = "$d"; do true; done
+d1=`date`
+$THIS_SH -c 'sleep 1&'
+d2=`date`
+test "$d1" = "$d2" || echo BAD
+echo End