From: jannick0 <jannick0@users.noreply.github.com>
Date: Sun, 7 Jan 2018 20:34:32 +0000 (+0100)
Subject: scanner: fix default of yy_top_state()
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=67b3e448727da3093cdc6f0ca7fd151fbf3c10ad;p=flex

scanner: fix default of yy_top_state()

For an _empty_ state stack the top of the state stack defaults to the state as if no state stack were present.

NB: sanity check for `yy_start_stack_ptr` could be added in `yy_top_state()`.
---

diff --git a/src/flex.skl b/src/flex.skl
index 1043238..05729df 100644
--- a/src/flex.skl
+++ b/src/flex.skl
@@ -2465,7 +2465,7 @@ m4_ifdef( [[M4_YY_NO_TOP_STATE]],,
 %endif
 {
     M4_YY_DECL_GUTS_VAR();
-	return YY_G(yy_start_stack)[YY_G(yy_start_stack_ptr) - 1];
+	return yy_start_stack_ptr > 0 ? YY_G(yy_start_stack)[YY_G(yy_start_stack_ptr) - 1] : YY_START;
 }
 ]])