segmentation fault when using clang_disposeIndex in a C ruby extension.

I am trying to create a litte ruby extension for the c interface of clang for fun. I have an Index class that create a CXIndex when the class is initialized.
User can set the options flags during the creation of the index like in this code:

index global options test

#Clangc::GlobalOptFlags.constants
#=> [:None, :Threadbackgroundpriorityforindexing, :Threadbackgroundpriorityforediting, :Threadbackgroundpriorityforall]

class TestIndexGlobalOptions < MiniTest::Test
def setup
@cindex = Clangc::Index.new(true, true)
end
def test_index_set_global_options_None
flags = Clangc::GlobalOptFlags::None
@cindex.global_options = flags
assert_equal flags, @cindex.global_options
end
def test_index_set_global_options_editing
flags = Clangc::GlobalOptFlags::Threadbackgroundpriorityforediting
@cindex.global_options = flags
assert_equal flags, @cindex.global_options
end
end

This code works, the problem is when the Garbage Collector (GC) of ruby try to clean the instances at the very end.
It generates a segmentation fault but just for the instances created with the flags Threadbackgroundpriorityforediting.

Each of my Index instance have a structure like this :

typedef struct Index_t {
CXIndex data;
} Index_t;

allocated with :

#include “class_Index.h”
#include “stdio.h”

static void
c_Index_struct_free(Index_t *s)
{
if(s)
{

if(s->data)
{
printf(“SENTINEL index ptr %p\n”, s->data);
clang_disposeIndex(s->data);
}
printf(“SENTINEL class ptr %p\n”, s);
ruby_xfree(s);
printf(“SENTINEL free end\n”);
}
}
static VALUE
c_Index_struct_alloc( VALUE klass)
{
Index_t *i;
i = (Index_t *) ruby_xmalloc(sizeof(Index_t)); //its an xmalloc
printf(“New class allocated at %p\n”, i);
i->data = NULL;
/*associate */
return Data_Wrap_Struct(klass, NULL, c_Index_struct_free,(void *) i );
}

The GC call c_Index_struct_free(Index_t *s) in order to clean all and the clang_disposeIndex instruction generate the segfault.

Here is the output (I have added some debugging output in my C code)

ruby test/Index_tests.rb
Run options: --seed 10378

Running:

New class allocated at 0x139bfe0
New class ptr 0x139bfe0 with Index ptr 0x1057b30
.New class allocated at 0x1350a30
New class ptr 0x1350a30 with Index ptr 0x13769f0
.

Finished in 0.000871s, 2297.2451 runs/s, 2297.2451 assertions/s.

2 runs, 2 assertions, 0 failures, 0 errors, 0 skips
SENTINEL index ptr 0x1057b30
SENTINEL class ptr 0x139bfe0
SENTINEL free end
SENTINEL index ptr 0x2013769f0
test/Index_tests.rb: [BUG] Segmentation fault at 0x0003e800002782
ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-linux]

– Control frame information -----------------------------------------------
c:0001 p:0000 s:0002 E:000f60 TOP [FINISH]

– Machine register context ------------------------------------------------
RIP: 0x00007f175c9cfb9d RBP: 0x0000000000de99f0 RSP: 0x00007ffc5a05a000
RAX: 0x0000000000000000 RBX: 0x00000002013769f0 RCX: 0x000000007fffffe1
RDX: 0x00007f175fb29970 RDI: 0x00000002013769f0 RSI: 0x000000000000001f
R8: 0x00000002013769f0 R9: 0x0000000000000000 R10: 0x00007f176018e700
R11: 0x0000000000000000 R12: 0x0000000001040000 R13: 0x0000000001042648
R14: 0x000000000103e060 R15: 0x00007ffc5a05a048 EFL: 0x0000000000010206

– C level backtrace information -------------------------------------------
/usr/lib/libruby.so.2.2 [0x7f175fcc2915]
/usr/lib/libruby.so.2.2 [0x7f175fcc2b4c]
/usr/lib/libruby.so.2.2 [0x7f175fb9cd4b]
/usr/lib/libruby.so.2.2 [0x7f175fc5432e]
/usr/lib/libc.so.6 [0x7f175f7bd540]
/usr/lib/libclang.so(clang_disposeIndex+0x1d) [0x7f175c9cfb9d]
/home/cedlemo/.gem/ruby/2.2.0/extensions/x86_64-linux/2.2.0/clangc-0.0.1/clangc/clangc.so(c_Index_struct_free+0x2c) [0x7f175d79ff7c]
/usr/lib/libruby.so.2.2 [0x7f175fbb3d21]
/usr/lib/libruby.so.2.2(rb_gc_call_finalizer_at_exit+0x289) [0x7f175fbbd169]
/usr/lib/libruby.so.2.2(ruby_cleanup+0x3e8) [0x7f175fba3668]
/usr/lib/libruby.so.2.2(ruby_run_node+0x25) [0x7f175fba38b5]
ruby [0x4008ab]
/usr/lib/libc.so.6(__libc_start_main+0xf0) [0x7f175f7aa800]
ruby(_start+0x29) [0x4008d9]

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