From: Nicholas Clark <nick@ccl4.org>
Date: Sat, 29 Dec 2007 19:50:27 +0000 (+0000)
Subject: In sv_chop(), write sentinals over the part of the buffer that is
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=50af2e611e4aecf342d3df7e3a9c906c5174ca05;p=p5sagit%2Fp5-mst-13.2.git

In sv_chop(), write sentinals over the part of the buffer that is
thrown away, and verify that they are present in sv_backoff().
assert that we are being asked to chop off positive amounts of buffer.

p4raw-id: //depot/perl@32778
---

diff --git a/sv.c b/sv.c
index bb64eb9..bf8d503 100644
--- a/sv.c
+++ b/sv.c
@@ -1403,6 +1403,16 @@ Perl_sv_backoff(pTHX_ register SV *sv)
     assert(SvTYPE(sv) != SVt_PVAV);
     if (SvIVX(sv)) {
 	const char * const s = SvPVX_const(sv);
+#ifdef DEBUGGING
+	/* Validate the preceding buffer's sentinals to verify that no-one is
+	   using it.  */
+	const U8 *p = (const U8*) s;
+	const U8 *const real_start = p - SvIVX(sv);
+	while (p > real_start) {
+	    --p;
+	    assert (*p == (U8)PTR2UV(p));
+	}
+#endif
 	SvLEN_set(sv, SvLEN(sv) + SvIVX(sv));
 	SvPV_set(sv, SvPVX(sv) - SvIVX(sv));
 	SvIV_set(sv, 0);
@@ -4215,6 +4225,7 @@ Perl_sv_chop(pTHX_ register SV *sv, register const char *ptr)
 	/* Nothing to do.  */
 	return;
     }
+    assert(ptr > SvPVX_const(sv));
     SV_CHECK_THINKFIRST(sv);
     if (SvTYPE(sv) < SVt_PVIV)
 	sv_upgrade(sv,SVt_PVIV);
@@ -4238,6 +4249,18 @@ Perl_sv_chop(pTHX_ register SV *sv, register const char *ptr)
     SvCUR_set(sv, SvCUR(sv) - delta);
     SvPV_set(sv, SvPVX(sv) + delta);
     SvIV_set(sv, SvIVX(sv) + delta);
+#ifdef DEBUGGING
+    {
+	/* Fill the preceding buffer with sentinals to verify that no-one is
+	   using it.  */
+	U8 *p = (U8*) SvPVX(sv);
+	const U8 *const real_start = p - SvIVX(sv);
+	while (p > real_start) {
+	    --p;
+	    *p = (U8)PTR2UV(p);
+	}
+    }
+#endif
 }
 
 /*