There is a memory leak in Ripper#sexp_raw with invalid syntax

I used the ruby_memcheck gem to find this leak.

Script to reproduce:¶

$ ruby_memcheck -e 'require "ripper"; Ripper.sexp_raw("break 1,;")' 

Stack trace¶

64 bytes in 1 blocks are definitely lost in loss record 8,335 of 11,879
  malloc (at /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
  objspace_xmalloc0 (gc.c:11465)
 *vtable_alloc_gen (ripper.y:6209)
 *local_push.constprop.0 (ripper.y:12587)
 *ripper_yyparse (ripper.y:1329)
 *ripper_parse0 (ripper.y:13817)
  rb_ensure (eval.c:997)
 *ripper_parse (ripper.y:13855)
  vm_call_cfunc_with_frame (vm_insnhelper.c:3037)
  vm_sendish (vm_insnhelper.c:4751)
  vm_exec_core (insns.def:778)
  rb_vm_exec (vm.c:2220)
  rb_ec_exec_node (eval.c:280)
  ruby_run_node (eval.c:321)
  main (main.c:47)

88 (24 direct, 64 indirect) bytes in 1 blocks are definitely lost in loss record 8,508 of 11,879
  malloc (at /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
  objspace_xmalloc0 (gc.c:11465)
 *vtable_alloc_gen (ripper.y:6206)
 *local_push.constprop.0 (ripper.y:12586)
 *ripper_yyparse (ripper.y:1329)
 *ripper_parse0 (ripper.y:13817)
  rb_ensure (eval.c:997)
 *ripper_parse (ripper.y:13855)
  vm_call_cfunc_with_frame (vm_insnhelper.c:3037)
  vm_sendish (vm_insnhelper.c:4751)
  vm_exec_core (insns.def:778)
  rb_vm_exec (vm.c:2220)
  rb_ec_exec_node (eval.c:280)
  ruby_run_node (eval.c:321)
  main (main.c:47)

Valgrind reported errors (e.g. memory leak or use-after-free) (RuntimeError)

Expected behavior¶

The Ripper#sexp_raw docs state that "By default, this method does not handle syntax errors in src, returning nil in such cases." Expected behavior, according to the documentation, would be nil returned without any memory leak