Ruby

@ohler55 mentioned in https://github.com/ohler55/oj/issues/501 that calling rb_id2name(SYM2ID(sym)) seems to lock symbols in memory but I couldn't find any issue open for that. So I'm just opening one just in case, but pls close if this is a dupe.

I created a sample C extension to reproduce this

#include "extconf.h" #include <stdlib.h> #include <stdio.h> #include <ruby.h>  VALUE rb_leak_sym(VALUE self, VALUE argument1) { const char*sym = rb_id2name(SYM2ID(argument1)); return Qnil; } void Init_testsym() { rb_define_global_function("leak_sym", rb_leak_sym, 1); } 

We can see it leaking memory with this snippet

require "testsym" require "objspace" def record_allocation GC.start GC.start puts "Before - Objects count: #{ObjectSpace.each_object.count}" puts "Before - Symbols count: #{Symbol.all_symbols.size}" yield GC.start GC.start puts "After - Objects count: #{ObjectSpace.each_object.count}" puts "After - Symbols count: #{Symbol.all_symbols.size}" end def leak_symbols 1_000_000.times.each { |i| leak_sym("string_number_#{i}".to_sym) } end record_allocation do leak_symbols end 

Output:

$ ruby -v test.rb ruby 2.4.4p296 (2018-03-28 revision 63013) [x86_64-darwin17] Before - Objects count: 8784 Before - Symbols count: 3063 After - Objects count: 2008786 After - Symbols count: 1003063