From: John Tobey <jtobey@user1.channel1.com>
Date: Tue, 24 Jun 1997 11:44:33 +0000 (+1200)
Subject: Re: Can't pack literals as pointers
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=72dbcb4b16ba8abae7db52f83482564e4d62acc4;p=p5sagit%2Fp5-mst-13.2.git

Re: Can't pack literals as pointers

MHO, pack("p","foo") should evaluate to a pointer that's valid in the
urrent context.  pack("p",undef) should return the NULL value.
urrently, they both produce the error "Modification of a read-only
alue attempted".

This looks pretty easy to fix, so I've prepared a diff against the
5.004_01 distribution.  This tests fine on my Linux.  I hope I'm not
introducing a memory leak or other ailment...

Credited: Tim Bunce <Tim.Bunce@ig.co.uk>
Credited: Gurusamy Sarathy <gsar@engin.umich.edu>
---

diff --git a/pp.c b/pp.c
index 1cea53f..fa36c50 100644
--- a/pp.c
+++ b/pp.c
@@ -3834,7 +3834,14 @@ PP(pp_pack)
 	case 'p':
 	    while (len-- > 0) {
 		fromstr = NEXTFROM;
-		aptr = SvPV_force(fromstr, na);	/* XXX Error if TEMP? */
+		if (fromstr == &sv_undef)
+		  aptr = NULL;
+		else {
+		  if (SvREADONLY(fromstr) && curcop != &compiling) {
+		    fromstr = sv_mortalcopy(fromstr);
+		  }
+		  aptr = SvPV_force(fromstr, na);
+		}
 		sv_catpvn(cat, (char*)&aptr, sizeof(char*));
 	    }
 	    break;