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C ABI and Versioning

The ABI exposed through include/native_message_box.h is designed to stay stable across additive evolution.

Versioning Rules

  • NMB_ABI_VERSION encodes major, minor, and patch.
  • Callers must pass the ABI version on structs that require it.
  • The runtime rejects mismatched major versions.

Struct Size Rule

Every public struct carries a struct_size field. Callers must initialize it with sizeof(struct).

That enables two important things:

  • Detection of truncated callers
  • Forward-compatible expansion of public structs

Memory Model

  • Input strings are UTF-8 and must stay alive for the duration of the call.
  • Output strings are allocator-owned and must be released through the owning allocator.
  • NmbAllocator allows the caller to override allocation policy.

Core Native Calls

Function Purpose
nmb_initialize Optional runtime initialization and logging setup
nmb_show_message_box Show a dialog and write the result
nmb_shutdown Release runtime state

Result Handling

Inspect both:

  • The returned NmbResultCode
  • The NmbMessageBoxResult payload for button, input, checkbox, timeout, and result code details