@let: bugfix: two free lists are needed.

When functions containing let are compiled, they leave nodes on
the let_free list. These nodes are of the wrong type for re-use
by the compilation of an external @let. That causes a crash.

Secondly, when we compile a function, we free the let_free list.
This is also bad, because if it contains nodes allocated by
the compilation of external lets, we would like those to be
re-used for subsequent external lets after that function, and
not to allocate new variables.

* awkgram.y (let_gfree): New static variable.
(statement): In the aftermath of the @let statement, when
returning the variable nodes to the free list, we now choose
which of the two free lists to return to based on whether
we are inside a function.
(add_let): Try to allocate from let_free if a function is
being compiled, otherwise from let_gfree.

1 files changed, 12 insertions, 6 deletions

diff --git a/awkgram.y b/awkgram.y
index 44a4a48c..285c233a 100644
--- a/awkgram.y
+++ b/awkgram.y
@@ -126,7 +126,8 @@ static enum {
 } want_param_names = DONT_CHECK;	/* ditto */
 static INSTRUCTION *in_function;	/* parsing kludge */
 static int in_loop;			/* parsing kludge */
-static NODE *let_free;			/* free list of lexical vars */
+static NODE *let_free;			/* free list of function lexical vars */
+static NODE *let_gfree;			/* free list of external lexical vars */
 static NODE *let_stack;			/* stack of allocated lexicals */
 static int rule = 0;
 
@@ -1066,6 +1067,8 @@ regular_loop:
 	  let_var_list_opt r_paren opt_nls statement
 	  {
 		NODE *old_let_stack = $2->memory;
+		NODE **pfreelist = in_function ? &let_free : &let_gfree;
+		NODE *freelist = *pfreelist;
 
 		if ($7 != NULL) {
 			merge_comments($7, NULL);
@@ -1085,12 +1088,14 @@ regular_loop:
 			/* pop from let stack */
 			let_stack = let->nxparam;
 			/* push onto free list */
-			let->nxparam = let_free;
-			let_free = let;
+			let->nxparam = freelist;
+			freelist = let;
 			/* scrub from symbol table */
 			remove_let(let);
 		}
 
+		*pfreelist = freelist;
+
 		yyerrok;
 	  }
 	| non_compound_stmt
@@ -5240,6 +5245,7 @@ add_let(INSTRUCTION *fi, INSTRUCTION *local)
 	NODE *f = fi != NULL ? fi->func_body : NULL;
 	const char *fname = f != NULL ? f->vname : NULL;
 	const char *name = estrdup(local->lextok, strlen(local->lextok));
+	NODE **pfreelist = in_function ? &let_free : &let_gfree;
 
 	/* Basic checks:*/
 	check_local(fname, name, local);
@@ -5249,10 +5255,10 @@ add_let(INSTRUCTION *fi, INSTRUCTION *local)
 	/*
 	 * Try to get lexical from the free list.
 	 */
-	if (let_free) {
+	if (*pfreelist) {
 		/* pop let from stack */
-		NODE *let = let_free;
-		let_free = let_free->nxparam;
+		NODE *let = *pfreelist;
+		*pfreelist = let->nxparam;
 		/* register in param or alias table under the given name */
 		install_let(let, name);
 		/* push onto let stack */