Disable $[ under 5.16

This adds the array_base feature to feature.pm

Perl_feature_is_enabled has been modified to use PL_curcop, rather
than PL_hintgv, so it can work with run-time hints as well.
(PL_curcop holds the current state op at run time, and &PL_compiling
at compile time, so it works for both.)  The hints in $^H are not
stored in the same place at compile time and run time, so the FEATURE_IS_ENABLED macro has been modified to check first whether
PL_curop == &PL_compiling.

Since array_base is on by default with no hint for it in %^H, it is
a ‘negative’ feature, whose entry in %^H turns it off.  feature.pm
has been modified to support such negative features.  The new FEATURE_IS_ENABLED_d can check whether such default features
are enabled.

This does make things less efficient, as every version declaration
now loads feature.pm to disable all features (including turning off
array_base, which entails adding an entry to %^H) before loading the
new bundle.  I have plans to make this more efficient.

1 files changed, 1 insertions, 1 deletions

diff --git a/proto.h b/proto.h
index 92befdac8a..eec052f413 100644
--- a/proto.h
+++ b/proto.h
@@ -990,7 +990,7 @@ PERL_CALLCONV char*	Perl_fbm_instr(pTHX_ unsigned char* big, unsigned char* bige
 #define PERL_ARGS_ASSERT_FBM_INSTR	\
 	assert(big); assert(bigend); assert(littlestr)
 
-PERL_CALLCONV bool	Perl_feature_is_enabled(pTHX_ const char *const name, STRLEN namelen)
+PERL_CALLCONV bool	Perl_feature_is_enabled(pTHX_ const char *const name, STRLEN namelen, bool negate)
 			__attribute__nonnull__(pTHX_1);
 #define PERL_ARGS_ASSERT_FEATURE_IS_ENABLED	\
 	assert(name)