There are some easy performance improvements to be had in release builds if ibus does what we do in the GNOME stack for GLib-based applications and libraries. Including:

• -Wl,-Bsymbolic and -fno-plt for libibus so you can call functions without extra indirection
• Use -Wl,-z,relro and -Wl,-z,now hardening options
• -DG_DISABLE_ASSERT so assertions compile out of stable builds
• -DG_DISABLE_CAST_CHECKS to avoid costly type system lookups in casts

Would this be desired by upstream? I can put together a configure.ac patch for it, though I was curious how it might be gated (e.g. --enable-release or something like that?)