Calling the same closure repeatedly consumes memory

[pipcet]

Test case:

use FFI::Platypus;
use FFI::TinyCC;

sub c {
}

my $tcc = FFI::TinyCC->new;

$tcc->compile_string(<<'EOF');
void c_with_arg(void (*f)(void))
{
    f();
}
EOF

my $ffi = FFI::Platypus->new;
$ffi->type('()->void', 'FType');

my $c = $ffi->closure(\&c);

my $a = $tcc->get_symbol('c_with_arg');

while(1) {
    $ffi->function($a => ['FType'] => 'int')->call($c);
}

When run, memory usage keeps increasing until the process is killed when the ulimit is hit. The expected result is that memory usage does not increase indefinitely.

It's not quite a memory leak, since we can reclaim memory by destroying the closure.

It's easy enough to see what causes this: the %cbdata hash in ::Closure keeps growing, since we call add_data for each invocation but never remove payload data.

However, there's no obvious (to me) fix. We could presumably get away with reusing the same ::ClosureData between invocations, but that would break the (pathological?) case in which the same ::Closure is used for different types of function pointer. A more complete fix would attach types to ::Closures.

[pipcet]

Sorry, this is an issue in FFI::Platypus, not FFI::Platypus::Lang::CPP.

[plicease]

This is not a use case that I considered.

In the very least it deserves a CAVEAT. One fix might be to cache the closure data based on the signature. Another that works Right Now to to cast the closure to an opaque like this:

use FFI::Platypus;
use FFI::TinyCC;

sub c {
}

my $tcc = FFI::TinyCC->new;

$tcc->compile_string(<<'EOF');
void c_with_arg(void (*f)(void))
{
    f();
}
EOF

my $ffi = FFI::Platypus->new;
$ffi->type('()->void', 'FType');

my $c = $ffi->closure(\&c);
my $c_ptr = $ffi->cast('()->void' => 'opaque', $c);

my $a = $tcc->get_symbol('c_with_arg');

while(1) {
    $ffi->function($a => ['opaque'] => 'int')->call($c_ptr);
}

That unfortunately pushes extra work on the developer to juggle both the clousre object and the closure pointer and closures are already hard enough to get right with FFI.

[plicease]

closing here, feel free to continue here:

https://github.com/plicease/FFI-Platypus/issues/40