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Allow an inner handle to be hot-swapped from inside a callback. #49

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Allow an inner handle to be hot-swapped from inside a callback. #49

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dcb2da0
Allow an inner handle to be hot-swapped from inside a callback.
robschaber Jun 23, 2017
a06b785
Fix improper test comparison in t/70callbacks.t
robschaber Jun 23, 2017
c14b45a
Get outer handle magic from the outer handle, not inner handle
robschaber Jun 23, 2017
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27 changes: 26 additions & 1 deletion DBI.xs
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Original file line number Diff line number Diff line change
Expand Up @@ -3594,6 +3594,13 @@ XS(XS_DBI_dispatch)
# endif
DEFSV_set(temp_defsv);

/* We probably localized a member of imp_xxh earlier (call_depth) so
* we need to keep a reference to its inner handle owner until the
* end of scope so that it can be restored if our callback swaps out
* the handle and tries to garbage collect it.
*/
sv_2mortal(newRV_inc(h));

EXTEND(SP, items+1);
PUSHMARK(SP);
PUSHs(orig_h); /* push outer handle, then others params */
Expand All @@ -3604,6 +3611,24 @@ XS(XS_DBI_dispatch)
outitems = call_sv(code, G_ARRAY); /* call the callback code */
MSPAGAIN;

/* Callback may have swapped out the inner handle from underneath us.
* If so, we need to refresh our vars (h, mg, imp_xxh) before dispatch.
*/
{
MAGIC *outer_magic = SvMAGIC(SvRV(orig_h));
if (outer_magic->mg_type != 'P')
outer_magic = mg_find(SvRV(orig_h), 'P');
if (outer_magic != mg) {
SV *inner_handle = outer_magic->mg_obj;
MAGIC *inner_magic = SvMAGIC(SvRV(inner_handle));
if (inner_magic->mg_type != DBI_MAGIC)
inner_magic = mg_find(SvRV(inner_handle), DBI_MAGIC);
mg = outer_magic;
h = ST(0) = inner_handle;
imp_xxh = (imp_xxh_t *)inner_magic->mg_ptr;
}
}

/* The callback code can undef $_ to indicate to skip dispatch */
skip_dispatch = !SvOK(DEFSV);
/* put $_ back now, but with an incremented ref count to compensate
Expand Down Expand Up @@ -5135,7 +5160,7 @@ take_imp_data(h)
PUSHMARK(sp);
XPUSHs(*hp);
PUTBACK;
call_method("finish", G_VOID);
call_method("finish", G_VOID|G_DISCARD);
SPAGAIN;
PUTBACK;
sv_unmagic(SvRV(*hp), 'P'); /* untie */
Expand Down
21 changes: 21 additions & 0 deletions t/70callbacks.t
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Original file line number Diff line number Diff line change
Expand Up @@ -232,6 +232,27 @@ my $stress_sth = $stress_dbh->prepare("select 1");
$stress_sth->{Callbacks}{execute} = sub { return; };
$stress_sth->execute(@params);

# Test that a db handle can be swapped out for a newly-created
# one from inside a callback with no ill effects.
{
my $dbh = DBI->connect($dsn);
my $old = tied %$dbh;
my $cb = sub {
my ($dbh) = @_;
my $new_dbh = DBI->connect($dsn);
$dbh->swap_inner_handle($new_dbh);
return;
};
$dbh->{Callbacks} = { ping => $cb };
no warnings qw/once redefine/;
local *DBD::ExampleP::db::ping = sub {
my ($new) = @_;
isnt $old, $new, 'inner handle replaced inside method';
};
$dbh->ping();
my $new = tied %$dbh;
isnt $old, $new, 'inner handle replaced after method';
}

done_testing();

Expand Down