use parallel\Runtime;
function a() { return; }
(new Runtime)->run(function() { a(); });

ZEND_INIT_FCALL_SPEC_CONST_HANDLER () at /home/rcm/Projects/thing/php-src/Zend/zend_vm_execute.h:4044
4044                    fbc = Z_FUNC_P(func);
(gdb) bt 
#0  ZEND_INIT_FCALL_SPEC_CONST_HANDLER () at /home/rcm/Projects/thing/php-src/Zend/zend_vm_execute.h:4044
#1  execute_ex (ex=0x7fffec004ef0) at /home/rcm/Projects/thing/php-src/Zend/zend_vm_execute.h:58907
#2  0x00007ffff7fab0eb in php_parallel_scheduler_run (frame=frame@entry=0x7ffff3a14020, runtime=0x7ffff545b280)
    at /home/rcm/Projects/thing/parallel/src/scheduler.c:331
#3  0x00007ffff7fab63f in php_parallel_thread (arg=0x7ffff545b280) at /home/rcm/Projects/thing/parallel/src/scheduler.c:501
#4  0x00007ffff7a98ded in ?? () from /usr/lib/libc.so.6
#5  0x00007ffff7b1c0dc in ?? () from /usr/lib/libc.so.6

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