---
title: "Compiler abstraction"
canonical_url: https://developer.repebble.com/pebbleos/docs/kernel/compiler/
last_updated: 2026-10-21
sdk_version: 4.33.1
---
# Compiler abstraction

Source: https://developer.repebble.com/pebbleos/docs/kernel/compiler/

`pbl/kernel/compiler.h` is the only place the tree may spell compiler specifics: attributes (`PBL_PACKED`, `PBL_WEAK`, `PBL_NAKED`, `PBL_SECTION()`, …) and builtins (`PBL_LIKELY()`, `PBL_RETURN_ADDRESS()`, `PBL_CLZ()`, …). It only covers what C23 does not: use `[[noreturn]]`, `[[maybe_unused]]`, `[[deprecated]]`, `unreachable()` and `ckd_add()`/`ckd_mul()` directly. Every public macro is declared and documented once in the frontend and expands to a `*_IMPL` counterpart from the backend selected by the predefined macros: `compiler/gcc.h` for GCC and `compiler/clang.h` for Clang, which reuses the GCC definitions and blanks the attributes Clang does not implement. Supporting another compiler means adding a backend that defines the same `*_IMPL` set and a branch in the frontend; callers stay untouched. The unit-test hooks built on these (`PBL_T_STATIC`, `PBL_T_MOCKABLE`) live in `pbl/util/testing.h`. Code outside `include/pbl/kernel/compiler/` must not use ` __attribute__ ` or `__builtin_*` directly. Exported headers follow the same rule: the SDK generator rewrites the macros into their GCC spellings, so the SDK ships no firmware headers; see [Building the SDK](https://developer.repebble.com/pebbleos/docs/sdk/building.md).

Generated from PebbleOS [3a7b71785](https://github.com/coredevices/pebbleos/commit/3a7b71785fd439666c4a8bc116f561140e8dec01). This page is maintained in the pebbleos repository: [docs/kernel/compiler.md](https://github.com/coredevices/pebbleos/blob/3a7b71785fd439666c4a8bc116f561140e8dec01/docs/kernel/compiler.md).