Don't use set_prompt(), but set prompt directly in emacs mode I-search.

set_prompt() also manipulates cur_prompt, which is not desired here.
This fixes a bug where command substitions in PS1 triggered a PS2
continuation after I-search (even when not desired).

issue reported by and ok marco@

bin/ksh/emacs.c

@@ -814,15 +814,19 @@ x_search_hist(int c)
 	int offset = -1;	/* offset of match in xbuf, else -1 */
 	char pat [256+1];	/* pattern buffer */
 	char *p = pat;
+	const char *oprompt;
 	int (*f)(int);
 
 	*p = '\0';
-	set_prompt(ISEARCH, NULL);
+	oprompt = prompt;
+	prompt = "I-search: ";
 	x_redraw(1);
 	while (1) {
 		x_flush();
-		if ((c = x_e_getc()) < 0)
+		if ((c = x_e_getc()) < 0) {
+			prompt = oprompt;
 			return (KSTD);
+		}
 		f = kb_find_hist_func(c);
 		if (c == CTRL('[')) {
 			/* might be part of an escape sequence */
@@ -866,9 +870,9 @@ x_search_hist(int c)
 			break;
 		}
 	}
-	set_prompt(PS1, NULL);
+	prompt = oprompt;
 	x_redraw(1);
-	return KSTD;
+	return (KSTD);
 }
 
 /* search backward from current line */

bin/ksh/lex.c

@@ -1180,9 +1180,6 @@ set_prompt(int to, Source *s)
 	case PS2: /* command continuation */
 		prompt = str_val(global("PS2"));
 		break;
-	case ISEARCH: /* incremental search */
-		prompt = "I-search: ";
-		break;
 	}
 }
 

bin/ksh/table.h

@@ -174,7 +174,6 @@ extern const struct builtin shbuiltins [], kshbuiltins [];
 /* values for set_prompt() */
 #define PS1	0		/* command */
 #define PS2	1		/* command continuation */
-#define ISEARCH	2		/* incremental search */
 
 EXTERN char *path;		/* copy of either PATH or def_path */
 EXTERN const char *def_path;	/* path to use if PATH not set */