kconfig: error out if recursive dependencies are found

Sample:
config FOO
	bool "This is foo"
	depends on BAR

config BAR
	bool "This is bar"
	depends on FOO

This will result in following error message:
error: found recursive dependency: FOO -> BAR -> FOO

And will then exit with exit code equal 1 so make will stop.
Inspired by patch from: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Adrian Bunk <bunk@stusta.de>
Cc: Roman Zippel <zippel@linux-m68k.org>

scripts/kconfig/symbol.c

@@ -786,13 +786,15 @@ static struct symbol *sym_check_expr_deps(struct expr *e)
 	return NULL;
 }
 
+/* return NULL when dependencies are OK */
 struct symbol *sym_check_deps(struct symbol *sym)
 {
 	struct symbol *sym2;
 	struct property *prop;
 
 	if (sym->flags & SYMBOL_CHECK) {
-		printf("Warning! Found recursive dependency: %s", sym->name);
+		fprintf(stderr, "%s:%d:error: found recursive dependency: %s",
+		        sym->prop->file->name, sym->prop->lineno, sym->name);
 		return sym;
 	}
 	if (sym->flags & SYMBOL_CHECKED)
@@ -816,13 +818,8 @@ struct symbol *sym_check_deps(struct symbol *sym)
 			goto out;
 	}
 out:
-	if (sym2) {
-		printf(" %s", sym->name);
-		if (sym2 == sym) {
-			printf("\n");
-			sym2 = NULL;
-		}
-	}
+	if (sym2)
+		fprintf(stderr, " -> %s%s", sym->name, sym2 == sym? "\n": "");
 	sym->flags &= ~SYMBOL_CHECK;
 	return sym2;
 }

scripts/kconfig/zconf.tab.c_shipped

@@ -2132,9 +2132,11 @@ void conf_parse(const char *name)
 	}
 	menu_finalize(&rootmenu);
 	for_all_symbols(i, sym) {
-		sym_check_deps(sym);
+		if (sym_check_deps(sym))
+			zconfnerrs++;
         }
-
+	if (zconfnerrs)
+		exit(1);
 	sym_set_change_count(1);
 }
 

scripts/kconfig/zconf.y

@@ -501,9 +501,11 @@ void conf_parse(const char *name)
 	}
 	menu_finalize(&rootmenu);
 	for_all_symbols(i, sym) {
-		sym_check_deps(sym);
+		if (sym_check_deps(sym))
+			zconfnerrs++;
         }
-
+	if (zconfnerrs)
+		exit(1);
 	sym_set_change_count(1);
 }