In @INC filters (subs returned by subs in @INC), $_ is localised to a
variable to which the next line of source code is to be assigned. The
function in pp_ctl.c that calls it (S_run_user_filter) has a pointer
to that variable.
Up till now, it was not setting the refcount or localising
$_ properly.
‘undef *_’ inside the sub would destroy the only refcount it
had, leaving a freed sv for toke.c to parse (which would crash,
of course).
In some cases, S_run_user_filter has to created a new variable. In
those cases, it was setting $_ to a mortal variable with the TEMP
flag, but with a refcount of 1, which would result in ‘Attempt to free
unreferenced scalar’ warnings if the $_ were freed by the subroutine.
This commit changes S_run_user_filter to use SAVEGENERICSV, rather
than SAVE_DEFSV, to localise $_, since the former lowers the refcount
on scope exit, while the latter does not. So now I have also made it
increase the refcount after assigning to the now-properly-localised $_
(DEFSV). I also turned off the TEMP flag, to avoid weird side effects
(which were what led me to this bug to begin with).
I'm going to use a mortal in case the upstream filter croaks. */
upstream = ((SvOK(buf_sv) && sv_len(buf_sv)) || SvGMAGICAL(buf_sv))
? sv_newmortal() : buf_sv;
+ SvTEMP_off(upstream);
SvUPGRADE(upstream, SVt_PV);
if (filter_has_file) {
int count;
ENTER_with_name("call_filter_sub");
- SAVE_DEFSV;
+ SAVEGENERICSV(GvSV(PL_defgv));
SAVETMPS;
EXTEND(SP, 2);
DEFSV_set(upstream);
+ SvREFCNT_inc_simple_void_NN(upstream);
PUSHMARK(SP);
mPUSHi(0);
if (filter_state) {
use Config;
use Filter::Util::Call;
-plan(tests => 143);
+plan(tests => 145);
unshift @INC, sub {
no warnings 'uninitialized';
\'like(__FILE__, qr/(?:GLOB|CODE)\(0x[0-9a-f]+\)/, "__FILE__ is valid");';
do $fh or die;
}
+
+# [perl #91880] $_ marked TEMP or having the wrong refcount inside a
+{ # filter sub
+ local @INC; local $|;
+ unshift @INC, sub { sub { undef *_; --$| }};
+ do "dah";
+ pass '$_ has the right refcount inside a filter sub';
+
+ my $temps = 0;
+ @INC = sub { sub {
+ my $temp = \sub{$_}->();
+ $temps++ if $temp == \$_;
+ $_ = "a" unless $|;
+ return --$|
+ }};
+ local $^W;
+ do "dah";
+
+ is $temps, 0, '$_ is not marked TEMP';
+}