From a72c271bac70ecc52cda8ed4ba689c8816509735 Mon Sep 17 00:00:00 2001
From: Nicholas Clark <nick@ccl4.org>
Date: Thu, 27 Jan 2005 19:26:21 +0000
Subject: [PATCH] Retrieve the flag bit that only 'p' uses, so that it is spare
 for future use.

p4raw-id: //depot/perl@23892
---
 genpacksizetables.pl | 12 ++++++------
 pp_pack.c            | 19 ++++++++++++++-----
 2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/genpacksizetables.pl b/genpacksizetables.pl
index b3e3a8c..2987499 100755
--- a/genpacksizetables.pl
+++ b/genpacksizetables.pl
@@ -7,10 +7,10 @@ use Encode;
 my @lines = grep {!/^#/} <DATA>;
 
 sub addline {
-  my ($arrays, $chrmap, $letter, $arrayname, $noone, $nocsum, $size,
+  my ($arrays, $chrmap, $letter, $arrayname, $spare, $nocsum, $size,
       $condition) = @_;
   my $line = "/* $letter */ $size";
-  $line .= " | PACK_SIZE_CANNOT_ONLY_ONE" if $noone;
+  $line .= " | PACK_SIZE_SPARE" if $spare;
   $line .= " | PACK_SIZE_CANNOT_CSUM" if $nocsum;
   $line .= ",";
   # And then the hack
@@ -24,7 +24,7 @@ sub output_tables {
 
   my $chrmap = shift;
   foreach (@_) {
-    my ($letter, $shriek, $noone, $nocsum, $size, $condition)
+    my ($letter, $shriek, $spare, $nocsum, $size, $condition)
       = /^([A-Za-z])(!?)\t(\S*)\t(\S*)\t([^\t\n]+)(?:\t+(.*))?$/;
     die "Can't parse '$_'" unless $size;
 
@@ -36,7 +36,7 @@ sub output_tables {
     }
 
     addline (\%arrays, $chrmap, $letter, $shriek ? 'shrieking' : 'normal',
-	     $noone, $nocsum, $size, $condition);
+	     $spare, $nocsum, $size, $condition);
   }
 
   my %earliest;
@@ -100,7 +100,7 @@ output_tables (\%ebcdicmap, @lines);
 print "#endif\n";
 
 __DATA__
-#Symbol	nooone	nocsum	size
+#Symbol	spare	nocsum	size
 c			char
 C			unsigned char
 U			char
@@ -126,7 +126,7 @@ N			=SIZE32
 V!			=SIZE32	PERL_PACK_CAN_SHRIEKSIGN
 N!			=SIZE32	PERL_PACK_CAN_SHRIEKSIGN
 L			=SIZE32
-p	*	*	char *
+p		*	char *
 w		*	char
 q			Quad_t	HAS_QUAD
 Q			Uquad_t	HAS_QUAD
diff --git a/pp_pack.c b/pp_pack.c
index 4136893..8f76d69 100644
--- a/pp_pack.c
+++ b/pp_pack.c
@@ -272,7 +272,7 @@ S_mul128(pTHX_ SV *sv, U8 m)
 #endif
 
 #define PACK_SIZE_CANNOT_CSUM		0x80
-#define PACK_SIZE_CANNOT_ONLY_ONE	0x40
+#define PACK_SIZE_SPARE			0x40
 #define PACK_SIZE_MASK			0x3F
 
 
@@ -329,7 +329,7 @@ unsigned char size_normal[53] = {
   0,
   /* n */ SIZE16,
   0,
-  /* p */ sizeof(char *) | PACK_SIZE_CANNOT_ONLY_ONE | PACK_SIZE_CANNOT_CSUM,
+  /* p */ sizeof(char *) | PACK_SIZE_CANNOT_CSUM,
 #if defined(HAS_QUAD)
   /* q */ sizeof(Quad_t),
 #else
@@ -398,7 +398,7 @@ unsigned char size_normal[99] = {
   0,
   /* n */ SIZE16,
   0,
-  /* p */ sizeof(char *) | PACK_SIZE_CANNOT_ONLY_ONE | PACK_SIZE_CANNOT_CSUM,
+  /* p */ sizeof(char *) | PACK_SIZE_CANNOT_CSUM,
 #if defined(HAS_QUAD)
   /* q */ sizeof(Quad_t),
 #else
@@ -935,7 +935,8 @@ S_unpack_rec(pTHX_ register tempsym_t* symptr, register char *s, char *strbeg, c
 	{
 	    int which = (symptr->code & TYPE_IS_SHRIEKING)
 		? PACK_SIZE_SHRIEKING : PACK_SIZE_NORMAL;
-	    int offset = TYPE_NO_MODIFIERS(datumtype) - packsize[which].first;
+	    const int rawtype = TYPE_NO_MODIFIERS(datumtype);
+	    int offset = rawtype - packsize[which].first;
 
 	    if (offset >= 0 && offset < packsize[which].size) {
 		/* Data about this template letter  */
@@ -948,9 +949,17 @@ S_unpack_rec(pTHX_ register tempsym_t* symptr, register char *s, char *strbeg, c
 		    if (len > howmany)
 			len = howmany;
 
+		    /* In the old code, 'p' was the only type without shortcut
+		       code to curtail unpacking to only one.  As far as I can
+		       see the only point of retaining this anomaly is to make
+		       code such as $_ = unpack "p2", pack "pI", "Hi", 2
+		       continue to segfault. ie, it probably should be
+		       construed as a bug.
+		    */
+
 		    if (!checksum || (data & PACK_SIZE_CANNOT_CSUM)) {
 			if (len && unpack_only_one &&
-			    !(data & PACK_SIZE_CANNOT_ONLY_ONE))
+			    rawtype != 'p')
 			    len = 1;
 			EXTEND(SP, len);
 			EXTEND_MORTAL(len);
-- 
2.7.4