From: Simon Cozens <simon@netthink.co.uk>
Date: Thu, 28 Dec 2000 20:33:13 +0000 (+0000)
Subject: Re: [PATCH] Warn on use of reference as array elem
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=d804643f1d3e26c9c696bb1ebe8344dd5f1c8f6d;p=p5sagit%2Fp5-mst-13.2.git

Re: [PATCH] Warn on use of reference as array elem
Message-ID: <20001228203313.A2607@deep-dark-truthful-mirror.perlhacker.org>

p4raw-id: //depot/perl@8234
---

diff --git a/pod/perldiag.pod b/pod/perldiag.pod
index abbdea7..be15926 100644
--- a/pod/perldiag.pod
+++ b/pod/perldiag.pod
@@ -3710,6 +3710,15 @@ old way has bad side effects.
 (D deprecated) This was an ill-advised attempt to emulate a poorly
 defined B<awk> feature.  Use an explicit printf() or sprintf() instead.
 
+=item Use of reference "%s" in array index
+
+(W) You tried to use a reference as an array index; this probably
+isn't what you mean, because references tend to be huge numbers which
+take you out of memory, and so usually indicates programmer error.
+
+If you really do mean it, explicitly numify your reference, like so: 
+C<$array[0+$ref]>
+
 =item Use of reserved word "%s" is deprecated
 
 (D deprecated) The indicated bareword is a reserved word.  Future
diff --git a/pp_hot.c b/pp_hot.c
index 2904d9f..a24aa1d 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -2815,12 +2815,15 @@ PP(pp_aelem)
 {
     djSP;
     SV** svp;
-    IV elem = POPi;
+    SV* elemsv = POPs;
+    IV elem = SvIV(elemsv);
     AV* av = (AV*)POPs;
     U32 lval = PL_op->op_flags & OPf_MOD;
     U32 defer = (PL_op->op_private & OPpLVAL_DEFER) && (elem > AvFILL(av));
     SV *sv;
 
+    if (SvROK(elemsv) && ckWARN(WARN_MISC))
+	Perl_warner(aTHX_ WARN_MISC, "Use of reference \"%s\" as array index", SvPV_nolen(elemsv));
     if (elem > 0)
 	elem -= PL_curcop->cop_arybase;
     if (SvTYPE(av) != SVt_PVAV)
diff --git a/t/pragma/warn/pp_hot b/t/pragma/warn/pp_hot
index 698255c..5dd0380 100644
--- a/t/pragma/warn/pp_hot
+++ b/t/pragma/warn/pp_hot
@@ -47,6 +47,9 @@
   Possible Y2K bug: about to append an integer to '19' [pp_concat]
     $x     = "19$yy\n";
 
+  Use of reference "%s" as array index [pp_aelem]
+    $x[\1]
+
 __END__
 # pp_hot.c [pp_print]
 use warnings 'unopened' ;
@@ -228,3 +231,17 @@ $x     = "19" . $yy . "\n";
 EXPECT
 Possible Y2K bug: about to append an integer to '19' at - line 12.
 Possible Y2K bug: about to append an integer to '19' at - line 13.
+########
+# pp_hot.c [pp_aelem]
+{
+use warnings 'misc';
+print $x[\1];
+}
+{
+no warnings 'misc';
+print $x[\1];
+}
+
+EXPECT
+OPTION regex
+Use of reference ".*" as array index at - line 4.