@ibuclaw I've got some problems backporting this hash_map. GCC < 5 doesn't have a hash_map. The pointer_map should work, but it doesn't provide a remove function. I think I can just set the values to NULL instead. This will require some changes, but it should work. pointer_map is also not integrated into the GCC garbage collector. If I mark labels as GTY((skip)) I'll have to allocate these manually instead of using ggc_alloc, right? AFAICS I can free the d_label_entry in pop_label?