Merge 76365c8 into facfab6

MANIFEST

@@ -5624,6 +5624,7 @@ t/lib/Devel/nodb.pm		Module for t/run/switchd.t
 t/lib/Devel/switchd.pm		Module for t/run/switchd.t
 t/lib/Devel/switchd_empty.pm	Module for t/run/switchd.t
 t/lib/Devel/switchd_goto.pm	Module for t/run/switchd.t
+t/lib/feature/autovivification	Tests for the autovivification feature
 t/lib/feature/bareword_filehandles	Tests for enabling/disabling bareword_filehandles feature
 t/lib/feature/bits		Tests for feature bit handling
 t/lib/feature/bundle		Tests for feature bundles

cop.h

@@ -576,6 +576,8 @@ string C<p>, creating the package if necessary.
 #define CopHINTHASH_get(c)	((COPHH*)((c)->cop_hints_hash))
 #define CopHINTHASH_set(c,h)	((c)->cop_hints_hash = (h))
 
+#define CopFEATURES_setfrom(c, o) ((c)->cop_features = (o)->cop_features)
+
 /*
 =for apidoc Am|SV *|cop_hints_fetch_pvn|const COP *cop|const char *keypv|STRLEN keylen|U32 hash|U32 flags
 

feature.h

@@ -12,24 +12,25 @@
 
 #define HINT_FEATURE_SHIFT	26
 
-#define FEATURE_BAREWORD_FILEHANDLES_BIT 0x0001
-#define FEATURE_BITWISE_BIT              0x0002
-#define FEATURE___SUB___BIT              0x0004
-#define FEATURE_MYREF_BIT                0x0008
-#define FEATURE_EVALBYTES_BIT            0x0010
-#define FEATURE_FC_BIT                   0x0020
-#define FEATURE_INDIRECT_BIT             0x0040
-#define FEATURE_ISA_BIT                  0x0080
-#define FEATURE_MULTIDIMENSIONAL_BIT     0x0100
-#define FEATURE_POSTDEREF_QQ_BIT         0x0200
-#define FEATURE_REFALIASING_BIT          0x0400
-#define FEATURE_SAY_BIT                  0x0800
-#define FEATURE_SIGNATURES_BIT           0x1000
-#define FEATURE_STATE_BIT                0x2000
-#define FEATURE_SWITCH_BIT               0x4000
-#define FEATURE_TRY_BIT                  0x8000
-#define FEATURE_UNIEVAL_BIT              0x10000
-#define FEATURE_UNICODE_BIT              0x20000
+#define FEATURE_AUTOVIVIFICATION_BIT     0x0001
+#define FEATURE_BAREWORD_FILEHANDLES_BIT 0x0002
+#define FEATURE_BITWISE_BIT              0x0004
+#define FEATURE___SUB___BIT              0x0008
+#define FEATURE_MYREF_BIT                0x0010
+#define FEATURE_EVALBYTES_BIT            0x0020
+#define FEATURE_FC_BIT                   0x0040
+#define FEATURE_INDIRECT_BIT             0x0080
+#define FEATURE_ISA_BIT                  0x0100
+#define FEATURE_MULTIDIMENSIONAL_BIT     0x0200
+#define FEATURE_POSTDEREF_QQ_BIT         0x0400
+#define FEATURE_REFALIASING_BIT          0x0800
+#define FEATURE_SAY_BIT                  0x1000
+#define FEATURE_SIGNATURES_BIT           0x2000
+#define FEATURE_STATE_BIT                0x4000
+#define FEATURE_SWITCH_BIT               0x8000
+#define FEATURE_TRY_BIT                  0x10000
+#define FEATURE_UNIEVAL_BIT              0x20000
+#define FEATURE_UNICODE_BIT              0x40000
 
 #define FEATURE_BUNDLE_DEFAULT	0
 #define FEATURE_BUNDLE_510	1
@@ -167,6 +168,13 @@
 	 FEATURE_IS_ENABLED_MASK(FEATURE_UNICODE_BIT)) \
     )
 
+#define FEATURE_AUTOVIVIFICATION_IS_ENABLED \
+    ( \
+	CURRENT_FEATURE_BUNDLE <= FEATURE_BUNDLE_527 \
+     || (CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
+	 FEATURE_IS_ENABLED_MASK(FEATURE_AUTOVIVIFICATION_BIT)) \
+    )
+
 #define FEATURE_MULTIDIMENSIONAL_IS_ENABLED \
     ( \
 	CURRENT_FEATURE_BUNDLE <= FEATURE_BUNDLE_527 \
@@ -250,6 +258,14 @@ S_magic_sethint_feature(pTHX_ SV *keysv, const char *keypv, STRLEN keylen,
             }
             return;
 
+        case 'a':
+            if (keylen == sizeof("feature_autovivification")-1
+                 && memcmp(subf+1, "utovivification", keylen - sizeof("feature_")) == 0) {
+                mask = FEATURE_AUTOVIVIFICATION_BIT;
+                break;
+            }
+            return;
+
         case 'b':
             if (keylen == sizeof("feature_bareword_filehandles")-1
                  && memcmp(subf+1, "areword_filehandles", keylen - sizeof("feature_")) == 0) {

lib/feature.pm

@@ -24,18 +24,19 @@ our %feature = (
     unicode_eval         => 'feature_unieval',
     declared_refs        => 'feature_myref',
     unicode_strings      => 'feature_unicode',
+    autovivification     => 'feature_autovivification',
     multidimensional     => 'feature_multidimensional',
     bareword_filehandles => 'feature_bareword_filehandles',
 );
 
 our %feature_bundle = (
-    "5.10"    => [qw(bareword_filehandles indirect multidimensional say state switch)],
-    "5.11"    => [qw(bareword_filehandles indirect multidimensional say state switch unicode_strings)],
-    "5.15"    => [qw(bareword_filehandles current_sub evalbytes fc indirect multidimensional say state switch unicode_eval unicode_strings)],
-    "5.23"    => [qw(bareword_filehandles current_sub evalbytes fc indirect multidimensional postderef_qq say state switch unicode_eval unicode_strings)],
-    "5.27"    => [qw(bareword_filehandles bitwise current_sub evalbytes fc indirect multidimensional postderef_qq say state switch unicode_eval unicode_strings)],
-    "all"     => [qw(bareword_filehandles bitwise current_sub declared_refs evalbytes fc indirect isa multidimensional postderef_qq refaliasing say signatures state switch try unicode_eval unicode_strings)],
-    "default" => [qw(bareword_filehandles indirect multidimensional)],
+    "5.10"    => [qw(autovivification bareword_filehandles indirect multidimensional say state switch)],
+    "5.11"    => [qw(autovivification bareword_filehandles indirect multidimensional say state switch unicode_strings)],
+    "5.15"    => [qw(autovivification bareword_filehandles current_sub evalbytes fc indirect multidimensional say state switch unicode_eval unicode_strings)],
+    "5.23"    => [qw(autovivification bareword_filehandles current_sub evalbytes fc indirect multidimensional postderef_qq say state switch unicode_eval unicode_strings)],
+    "5.27"    => [qw(autovivification bareword_filehandles bitwise current_sub evalbytes fc indirect multidimensional postderef_qq say state switch unicode_eval unicode_strings)],
+    "all"     => [qw(autovivification bareword_filehandles bitwise current_sub declared_refs evalbytes fc indirect isa multidimensional postderef_qq refaliasing say signatures state switch try unicode_eval unicode_strings)],
+    "default" => [qw(autovivification bareword_filehandles indirect multidimensional)],
 );
 
 $feature_bundle{"5.12"} = $feature_bundle{"5.11"};
@@ -429,6 +430,14 @@ C<try> are caught by executing the body of the C<catch> block.
 
 For more information, see L<perlsyn/"Try Catch Exception Handling">.
 
+=head2 The 'autovivification' feature.
+
+This feature enables autovivification of references.  It is enabled by
+default, but can be turned off to disable it.
+
+This feature is available under this name from Perl 5.34 onwards, in
+previous versions it was simple on all the time.
+
 =head1 FEATURE BUNDLES
 
 It's possible to load multiple features together, using
@@ -442,64 +451,68 @@ The following feature bundles are available:
   bundle    features included
   --------- -----------------
   :default  indirect multidimensional
-            bareword_filehandles
+            bareword_filehandles autovivification
+
+  :5.10     autovivification bareword_filehandles
+            indirect multidimensional say state switch
+
+  :5.12     autovivification bareword_filehandles
+            indirect multidimensional say state switch
+            unicode_strings
 
-  :5.10     bareword_filehandles indirect
+  :5.14     autovivification bareword_filehandles
+            indirect multidimensional say state switch
+            unicode_strings
+
+  :5.16     autovivification bareword_filehandles
+            current_sub evalbytes fc indirect
             multidimensional say state switch
+            unicode_eval unicode_strings
 
-  :5.12     bareword_filehandles indirect
+  :5.18     autovivification bareword_filehandles
+            current_sub evalbytes fc indirect
             multidimensional say state switch
-            unicode_strings
+            unicode_eval unicode_strings
 
-  :5.14     bareword_filehandles indirect
+  :5.20     autovivification bareword_filehandles
+            current_sub evalbytes fc indirect
             multidimensional say state switch
-            unicode_strings
+            unicode_eval unicode_strings
 
-  :5.16     bareword_filehandles current_sub evalbytes
-            fc indirect multidimensional say state
-            switch unicode_eval unicode_strings
+  :5.22     autovivification bareword_filehandles
+            current_sub evalbytes fc indirect
+            multidimensional say state switch
+            unicode_eval unicode_strings
 
-  :5.18     bareword_filehandles current_sub evalbytes
-            fc indirect multidimensional say state
+  :5.24     autovivification bareword_filehandles
+            current_sub evalbytes fc indirect
+            multidimensional postderef_qq say state
             switch unicode_eval unicode_strings
 
-  :5.20     bareword_filehandles current_sub evalbytes
-            fc indirect multidimensional say state
+  :5.26     autovivification bareword_filehandles
+            current_sub evalbytes fc indirect
+            multidimensional postderef_qq say state
             switch unicode_eval unicode_strings
 
-  :5.22     bareword_filehandles current_sub evalbytes
-            fc indirect multidimensional say state
+  :5.28     autovivification bareword_filehandles
+            bitwise current_sub evalbytes fc indirect
+            multidimensional postderef_qq say state
             switch unicode_eval unicode_strings
 
-  :5.24     bareword_filehandles current_sub evalbytes
-            fc indirect multidimensional postderef_qq
-            say state switch unicode_eval
-            unicode_strings
-
-  :5.26     bareword_filehandles current_sub evalbytes
-            fc indirect multidimensional postderef_qq
-            say state switch unicode_eval
-            unicode_strings
-
-  :5.28     bareword_filehandles bitwise current_sub
-            evalbytes fc indirect multidimensional
-            postderef_qq say state switch unicode_eval
-            unicode_strings
-
-  :5.30     bareword_filehandles bitwise current_sub
-            evalbytes fc indirect multidimensional
-            postderef_qq say state switch unicode_eval
-            unicode_strings
+  :5.30     autovivification bareword_filehandles
+            bitwise current_sub evalbytes fc indirect
+            multidimensional postderef_qq say state
+            switch unicode_eval unicode_strings
 
-  :5.32     bareword_filehandles bitwise current_sub
-            evalbytes fc indirect multidimensional
-            postderef_qq say state switch unicode_eval
-            unicode_strings
+  :5.32     autovivification bareword_filehandles
+            bitwise current_sub evalbytes fc indirect
+            multidimensional postderef_qq say state
+            switch unicode_eval unicode_strings
 
-  :5.34     bareword_filehandles bitwise current_sub
-            evalbytes fc indirect multidimensional
-            postderef_qq say state switch unicode_eval
-            unicode_strings
+  :5.34     autovivification bareword_filehandles
+            bitwise current_sub evalbytes fc indirect
+            multidimensional postderef_qq say state
+            switch unicode_eval unicode_strings
 
 The C<:default> bundle represents the feature set that is enabled before
 any C<use feature> or C<no feature> declaration.

op.c

@@ -9423,6 +9423,7 @@ Perl_newSTATEOP(pTHX_ I32 flags, char *label, OP *o)
     cop->cop_seq = seq;
     cop->cop_warnings = DUP_WARNINGS(PL_curcop->cop_warnings);
     CopHINTHASH_set(cop, cophh_copy(CopHINTHASH_get(PL_curcop)));
+    CopFEATURES_setfrom(cop, PL_curcop);
     if (label) {
 	Perl_cop_store_label(aTHX_ cop, label, strlen(label), utf8);
 

pp_hot.c

@@ -35,6 +35,7 @@
 #define PERL_IN_PP_HOT_C
 #include "perl.h"
 #include "regcomp.h"
+#include "feature.h"
 
 /* Hot code. */
 
@@ -5434,6 +5435,21 @@ Perl_vivify_ref(pTHX_ SV *sv, U32 to_what)
     if (!SvOK(sv)) {
         if (SvREADONLY(sv))
             Perl_croak_no_modify();
+        if (!FEATURE_AUTOVIVIFICATION_IS_ENABLED) {
+            const char *type = "an unknown";
+            switch (to_what) {
+            case OPpDEREF_SV:
+                type = "a scalar";
+                break;
+            case OPpDEREF_AV:
+                type = "an array";
+                break;
+            case OPpDEREF_HV:
+                type = "a hash";
+                break;
+            }
+            Perl_croak(aTHX_ "Attempt to autovivify %s reference with autovivification disabled", type);
+        }
         prepare_SV_for_RV(sv);
         switch (to_what) {
         case OPpDEREF_SV:

regen/feature.pl

@@ -41,6 +41,7 @@ BEGIN
     multidimensional => 'multidimensional',
     bareword_filehandles => 'bareword_filehandles',
     try             => 'try',
+    autovivification => 'autovivification',
 );
 
 # NOTE: If a feature is ever enabled in a non-contiguous range of Perl
@@ -50,15 +51,16 @@ BEGIN
 # 5.odd implies the next 5.even, but an explicit 5.even can override it.
 
 # features bundles
-use constant V5_9_5 => sort qw{say state switch indirect multidimensional bareword_filehandles};
+use constant V5_9_5 =>
+   sort qw{say state switch indirect multidimensional bareword_filehandles autovivification};
 use constant V5_11  => sort ( +V5_9_5, qw{unicode_strings} );
 use constant V5_15  => sort ( +V5_11, qw{unicode_eval evalbytes current_sub fc} );
 use constant V5_23  => sort ( +V5_15, qw{postderef_qq} );
 use constant V5_27  => sort ( +V5_23, qw{bitwise} );
 
 my %feature_bundle = (
     all     => [ sort keys %feature ],
-    default => [ qw{indirect multidimensional bareword_filehandles} ],
+    default => [ qw{indirect multidimensional bareword_filehandles autovivification} ],
     # using 5.9.5 features bundle
     "5.9.5" => [ +V5_9_5 ],
     "5.10"  => [ +V5_9_5 ],
@@ -835,6 +837,14 @@ =head2 The 'try' feature.
 
 For more information, see L<perlsyn/"Try Catch Exception Handling">.
 
+=head2 The 'autovivification' feature.
+
+This feature enables autovivification of references.  It is enabled by
+default, but can be turned off to disable it.
+
+This feature is available under this name from Perl 5.34 onwards, in
+previous versions it was simple on all the time.
+
 =head1 FEATURE BUNDLES
 
 It's possible to load multiple features together, using

t/lib/feature/autovivification

@@ -0,0 +1,50 @@
+Test the autovivification feature
+
+__END__
+# NAME hash autovivification
+use feature 'say'; # ensure the autoviv test depends on cop_warnings, not cop_hints
+my $x;
+$x->{foo} = 1;
+no feature 'autovivification';
+undef $x;
+$x->{foo} = 1;
+EXPECT
+Attempt to autovivify a hash reference with autovivification disabled at - line 6.
+########
+# NAME hash autovivification (subhash)
+use feature 'say'; # ensure the autoviv test depends on cop_warnings, not cop_hints
+my $x = {};
+$x->{foo} = 1;
+$x->{foo}{bar} = 1;
+no feature 'autovivification';
+$x = {};
+$x->{foo}{bar} = 1;
+EXPECT
+Attempt to autovivify a hash reference with autovivification disabled at - line 7.
+########
+# NAME array autovivification
+my $x;
+$x->[0] = 1;
+undef $x;
+no feature 'autovivification';
+$x->[0] = 2;
+EXPECT
+Attempt to autovivify an array reference with autovivification disabled at - line 5.
+########
+# NAME array autovivification (sub array)
+my $x = {};
+$x->{foo}[0] = 1;
+$x = {};
+no feature 'autovivification';
+$x->{foo}[0] = 2;
+EXPECT
+Attempt to autovivify an array reference with autovivification disabled at - line 5.
+########
+# NAME scalar autovivification
+my $x;
+$$x = 1;
+undef $x;
+no feature 'autovivification';
+$$x = 2;
+EXPECT
+Attempt to autovivify a scalar reference with autovivification disabled at - line 5.