parser: change LABEL type from pval to opval

The items pushed onto the parser stack can be one of several types:
ival, opval, pval etc. The only remaining use of pval is when a "label:"
is encountered.

When an error occurs during parsing, ops on the parse stack get
automatically reaped these days as part of the OP slab mechanism;
but bare strings (pvals) still leak.

Convert this one remaining pval into an opval, making the toker return
an OP_CONST with an SV holding the label.

Since newSTATEOP() still expects a raw string for the label, the parser
just grabs the value returned by the toker and makes a copy of the
string from it, then immediately frees the OP_CONST and its associated
SV.

The leak was showing up in ext/XS-APItest/t/stmtasexpr.t, which expects
to parse a statement where labels are banned.

1 files changed, 9 insertions, 3 deletions

diff --git a/perly.y b/perly.y
index da0b3e364a..1170df80f2 100644
--- a/perly.y
+++ b/perly.y
@@ -50,7 +50,7 @@
 %token <opval> BAREWORD METHOD FUNCMETH THING PMFUNC PRIVATEREF QWLIST
 %token <opval> FUNC0OP FUNC0SUB UNIOPSUB LSTOPSUB
 %token <opval> PLUGEXPR PLUGSTMT
-%token <pval> LABEL
+%token <opval> LABEL
 %token <ival> FORMAT SUB SIGSUB ANONSUB ANON_SIGSUB PACKAGE USE
 %token <ival> WHILE UNTIL IF UNLESS ELSE ELSIF CONTINUE FOR
 %token <ival> GIVEN WHEN DEFAULT
@@ -253,11 +253,17 @@ fullstmt:	barestmt
 
 labfullstmt:	LABEL barestmt
 			{
-			  $$ = newSTATEOP(SVf_UTF8 * $1[strlen($1)+1], $1, $2);
+                          SV *label = cSVOPx_sv($1);
+			  $$ = newSTATEOP(SvFLAGS(label) & SVf_UTF8,
+                                            savepv(SvPVX_const(label)), $2);
+                          op_free($1);
 			}
 	|	LABEL labfullstmt
 			{
-			  $$ = newSTATEOP(SVf_UTF8 * $1[strlen($1)+1], $1, $2);
+                          SV *label = cSVOPx_sv($1);
+			  $$ = newSTATEOP(SvFLAGS(label) & SVf_UTF8,
+                                            savepv(SvPVX_const(label)), $2);
+                          op_free($1);
 			}
 	;