ASCII art diagram:
INTERFACE IMPLEMENTATION
+-----------------------+
|libir++.h |
| |
|C++ bindings to libir.h|
+-----------------------+
|
+-----------------------+ +-------------------------+
|libir.h | |libir-impl.h |
| | | |
|Pure C API |---------|C++ abstract base classes|
|Everything is opaque | |for implementing an IR |
|Uses no GCC headers | |"provider" |
+-----------------------+ +-------------------------+
|
|--------------------------+
| |
+-------------------------+ +-------------------------+
|libir-gcc-plugin.cc | |Other IR providers |
| | | |
|Implementation for GCC | |e.g. libgccjit |
|plugins | +-------------------------+
+-------------------------+
Linkage model
+---------------------------+
+-------------------------+ |libir-gcc-plugin.so |
|cc1, cc1plus, etc | | |
| | | +-----------------------+ |
| dlopen "foo-plugin.so | | |libir-gcc-plugin.cc | |
| | | | | | |
| | dlsym "init_plugin"-----------------> "init_plugin" | |
| | | | +----------|------------+ |
+---|---------------------+ | | calls |
| +------------|--------+-----+
| | | linked
| dlopen +----------------|--------+-+
+------------------------------>| foo-plugin.so V |
| "init_libir_plugin" |
+---------------------------+