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Allow can() to take a list of methods #22405

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Allow can() to take a list of methods #22405

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9784e88
Update UNIVERSAL::can() to accept a list of methods to check for
Ovid Jul 14, 2024
59dfd9f
no need to iterate over our args twice.
Ovid Jul 14, 2024
a0a3c76
Add me to AUTHORS
Ovid Jul 14, 2024
4795c9c
Make sure we extend the stack before we start modifying it
Ovid Jul 15, 2024
f2b6d8f
Return nothing, instead of undef, when can() is called with missing m…
Ovid Jul 15, 2024
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Update UNIVERSAL::can() to accept a list of methods to check for
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@Ovid
Ovid committed Jul 15, 2024
commit 9784e88bb51f05de86f9cb7b63c411004084afa1
37 changes: 36 additions & 1 deletion t/uni/universal.t
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@ BEGIN {
use utf8;
use open qw( :utf8 :std );

plan tests => 90;
plan tests => 103;

$a = {};
bless $a, "Bòb";
Expand Down Expand Up @@ -159,4 +159,39 @@ ok (!splàtt->isa('plòp'));
ok (!splàtt->isa('zlòpp'));
ok (splàtt->isa('plòp'));

#
# Check that ->can() can now accept a list of methods
#

package Parent {
sub new { return bless {}, shift }
sub foo { return __PACKAGE__ }
sub bar { return __PACKAGE__ }
}
package Child {
our @ISA = qw(Parent);
sub bar { return __PACKAGE__ }
sub baz { return __PACKAGE__ }
}

my $foo = \&Parent::foo;
my $parent_bar = \&Parent::bar;
my $child_bar = \&Child::bar;
my $baz = \&Child::baz;

ok( my @methods = Child->can(qw(foo bar baz)) );
is(scalar @methods, 3, 'should return 3 methods');
is( builtin::refaddr($methods[0]), builtin::refaddr($foo), 'foo should return our parent method' );
is( builtin::refaddr($methods[1]), builtin::refaddr($child_bar), 'bar should return our child method');
is( builtin::refaddr($methods[2]), builtin::refaddr($baz), 'baz should return our child method' );
ok( Child->can(qw(foo bar baz)), 'can(@methods) in scalar content should return a true value' );

my $child = Child->new;
ok( @methods = $child->can(qw(bar baz)) );
is(scalar @methods, 2, 'should return 2 methods');
is( builtin::refaddr($methods[0]), builtin::refaddr($child_bar), 'bar should return our child method' );
is( builtin::refaddr($methods[1]), builtin::refaddr($baz), 'baz should return our child method' );
ok( scalar $child->can(qw(bar baz)), 'can(@methods) in scalar content should return a true value' );

ok( !Child->can(qw(foo baz no_such_method)), 'can(@methods) with non-existent methods should already return nothing' );
ok( !scalar Child->can(qw(foo baz no_such_method)), 'can(@methods) with non-existent methods should return false in scalar context' );
28 changes: 16 additions & 12 deletions universal.c
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Expand Up @@ -469,21 +469,19 @@ XS(XS_UNIVERSAL_import_unimport)
XSRETURN_EMPTY;
}


XS(XS_UNIVERSAL_can); /* prototype to pass -Wmissing-prototypes */
XS(XS_UNIVERSAL_can)
{
dXSARGS;
SV *sv;
SV *rv;
HV *pkg = NULL;
GV *iogv;
int i;

if (items != 2)
croak_xs_usage(cv, "object-ref, method");
if (items < 2)
croak_xs_usage(cv, "object-ref, method, ...");

sv = ST(0);

SvGETMAGIC(sv);

/* Reject undef and empty string. Note that the string form takes
Expand All @@ -492,8 +490,6 @@ XS(XS_UNIVERSAL_can)
if (!SvOK(sv) || (SvPOK(sv) && !SvCUR(sv)))
XSRETURN_UNDEF;

rv = &PL_sv_undef;

if (SvROK(sv)) {
sv = MUTABLE_SV(SvRV(sv));
if (SvOBJECT(sv))
Expand All @@ -512,13 +508,21 @@ XS(XS_UNIVERSAL_can)
}

if (pkg) {
GV * const gv = gv_fetchmethod_sv_flags(pkg, ST(1), 0);
if (gv && isGV(gv))
rv = sv_2mortal(newRV(MUTABLE_SV(GvCV(gv))));
for (i = 1; i < items; i++) {
GV * const gv = gv_fetchmethod_sv_flags(pkg, ST(i), 0);
if (!gv || !isGV(gv) || !GvCV(gv))
XSRETURN_UNDEF;
}

EXTEND(SP, items - 1);
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@tonycoz tonycoz Jul 15, 2024

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You moved the writes to the stack before the EXTEND(), which may write beyond the end of the stack, the EXTEND should be moved above the loop.
for (i = 1; i < items; i++) {
GV * const gv = gv_fetchmethod_sv_flags(pkg, ST(i), 0);
ST(i-1) = sv_2mortal(newRV(MUTABLE_SV(GvCV(gv))));
}
XSRETURN(items - 1);
}

ST(0) = rv;
XSRETURN(1);
XSRETURN_UNDEF;
}

XS(XS_UNIVERSAL_DOES); /* prototype to pass -Wmissing-prototypes */
Expand Down