From: Dave Mitchell <davem@fdisolutions.com>
Date: Sat, 27 May 2006 21:16:30 +0000 (+0000)
Subject: fix eval qw(BEGIN{die}) style leaks.
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=eb7d7d25d2f780edcbedc124a5bdca0d53ad8687;p=p5sagit%2Fp5-mst-13.2.git

fix eval qw(BEGIN{die}) style leaks.
death while exdcuting code while parsing meant that the current
parse stack got quiety abandonded, thus leaking a bunch of OPs.
Register a destructor to be called when this happens.

p4raw-id: //depot/perl@28319
---

diff --git a/perly.c b/perly.c
index 77525f8..888c6ea 100644
--- a/perly.c
+++ b/perly.c
@@ -245,6 +245,38 @@ yystpcpy (pTHX_ char *yydest, const char *yysrc)
 
 #endif /* !YYERROR_VERBOSE */
 
+
+/* a snapshot of the current stack position variables for use by
+ * S_clear_yystack */
+
+typedef struct {
+    short *yyss;
+    short *yyssp;
+    YYSTYPE *yyvsp;
+    int yylen;
+} yystack_positions;
+
+/* called during cleanup (via SAVEDESTRUCTOR_X) to free any items on the
+ * parse stack, thus avoiding leaks if we die  */
+
+static void
+S_clear_yystack(pTHX_ const void *p)
+{
+    yystack_positions *y = (yystack_positions*) p;
+
+    if (!y->yyss)
+	return;
+    YYDPRINTF ((Perl_debug_log, "clearing the parse stack\n"));
+    y->yyvsp -= y->yylen; /* ignore the tokens that have just been reduced */
+    y->yyssp -= y->yylen;
+    while (y->yyssp > y->yyss) {
+	if (yy_is_opval[yystos[*y->yyssp]])
+	    op_free(y->yyvsp->opval);
+	y->yyvsp--;
+	y->yyssp--;
+    }
+}
+
 /*----------.
 | yyparse.  |
 `----------*/
@@ -283,6 +315,8 @@ Perl_yyparse (pTHX)
     /* for ease of re-allocation and automatic freeing, have two SVs whose
       * SvPVX points to the stacks */
     SV *yyss_sv, *yyvs_sv;
+    SV *ss_save_sv;
+    yystack_positions *ss_save;
 
 #ifdef DEBUGGING
     /* maintain also a stack of token/rule names for debugging with -Dpv */
@@ -320,10 +354,18 @@ Perl_yyparse (pTHX)
 
     yyss_sv = newSV(YYINITDEPTH * sizeof(short));
     yyvs_sv = newSV(YYINITDEPTH * sizeof(YYSTYPE));
+    ss_save_sv = newSV(sizeof(yystack_positions));
     SAVEFREESV(yyss_sv);
     SAVEFREESV(yyvs_sv);
+    SAVEFREESV(ss_save_sv);
     yyss = (short *) SvPVX(yyss_sv);
     yyvs = (YYSTYPE *) SvPVX(yyvs_sv);
+    ss_save = (yystack_positions *) SvPVX(ss_save_sv);
+
+    ss_save->yyss = NULL; /* disarm stack cleanup */
+    /* cleanup the parse stack on premature exit */
+    SAVEDESTRUCTOR_X(S_clear_yystack, (void*) ss_save);
+
     /* note that elements zero of yyvs and yyns are not used */
     yyssp = yyss;
     yyvsp = yyvs;
@@ -340,8 +382,6 @@ Perl_yyparse (pTHX)
     yynerrs = 0;
     yychar = YYEMPTY;		/* Cause a token to be read.  */
 
-
-
     YYDPRINTF ((Perl_debug_log, "Entering state %d\n", yystate));
 
     goto yysetstate;
@@ -507,6 +547,15 @@ Perl_yyparse (pTHX)
 
 
     YY_REDUCE_PRINT (yyn);
+
+    /* running external code may trigger a die (eg 'use nosuchmodule'):
+     * record the current stack state so that an unwind will
+     * free all the pesky OPs lounging around on the parse stack */
+    ss_save->yyss = yyss;
+    ss_save->yyssp = yyssp;
+    ss_save->yyvsp = yyvsp;
+    ss_save->yylen = yylen;
+
     switch (yyn) {
 
 /* contains all the rule actions; auto-generated from perly.y */
@@ -716,7 +765,8 @@ Perl_yyparse (pTHX)
 
   yyreturn:
 
-    LEAVE;			/* force stack free before we return */
+    ss_save->yyss = NULL;	/* disarm parse stack cleanup */
+    LEAVE;		/* force stack free before we return */
 
     return yyresult;
 }