-fbounds-safety: Enforcing bounds safety for C

9 days ago

-fbounds-safety is a C extension designed to enforce bounds safety and prevent out-of-bounds (OOB) memory accesses.
The extension introduces bounds annotations (e.g., __counted_by, __sized_by, __ended_by) to attach bounds information to pointers.
Compiler inserts bounds checks on pointer dereferences to ensure memory access remains within specified bounds.
Reduces annotation burden by using implicit wide pointers (fat pointers) for local variables while preserving ABI compatibility.
Supports incremental adoption, allowing partial implementation while still providing safety benefits.
Ensures deterministic traps on bounds violations instead of undefined behavior.
Includes annotations for single objects (__single), sentinel-delimited arrays (__null_terminated, __terminated_by), and interoperability with unsafe code (__unsafe_indexable).
Default bounds annotations are applied based on ABI visibility (__single for ABI-visible pointers, __bidi_indexable for locals).
Maintains correctness of bounds annotations through compile-time restrictions and run-time checks.
Provides cast rules to prevent unsafe conversions between pointers with different bounds attributes.
Includes portability mechanisms (e.g., toolchain header) for compatibility with non-supporting toolchains.
Limitations include reliance on run-time checks and no guarantees for type safety beyond bounds violations.

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