ra8_sbrk_trap.h File Reference

The newlib heap syscall, replaced by a halting trap. More...

#include <stddef.h>

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Functions
void *	_sbrk (ptrdiff_t incr)
	Trap that replaces newlib's heap-extension syscall.

Detailed Description

The newlib heap syscall, replaced by a halting trap.

Tag

[Ring 1 / CORE] {World: S}

NASA Power of 10 Rule 3 forbids dynamic allocation after init, and target firmware has no heap at all. Firmware is freestanding and links with -nostdlib without newlib or libnosys. Standard allocator calls fail closed at link time. ra8_sbrk_trap.c provides a defense-in-depth tripwire so any legacy or external routine attempting to invoke _sbrk halts safely via ra8_fatal_error.

Copyright

Copyright (c) 2026 Brighton Sikarskie SPDX-License-Identifier: MIT

Definition in file ra8_sbrk_trap.h.

Function Documentation

_sbrk()

void * _sbrk

(

ptrdiff_t

incr

)

Trap that replaces newlib's heap-extension syscall.

Reports a fatal error and never returns. Reaching this means something called malloc, calloc, realloc, strdup or a C++ operator new on the target, which the firmware's zero-heap design forbids – so it halts at the call site rather than handing back storage that does not exist.

Parameters

[in]

incr

Bytes newlib wants the program break advanced by. Ignored: the trap never satisfies the request.

Returns

Never returns. The signature matches newlib's expectation so the strong definition overrides the library's own.

Return values

NULL	Unreachable; present only to satisfy the newlib contract.

Precondition

The fatal-error sink is available (it is from reset).

The image linked this TU, so the trap overrides newlib's _sbrk.

Postcondition

Control never returns to the caller; the firmware halts.

The fatal-error sink has emitted the violation tag.

Note

Not thread-safe and not intended to be – it never returns.

Warning

Do not call this directly. It exists for the C library to resolve and for the host death-test to drive.

Example:

// Host death test: prove the trap never returns.
(void)_sbrk(32);  // does not come back

See also

ra8_fatal_error()

Since

0.1.0

Definition at line 45 of file ra8_sbrk_trap.c.

References ra8_fatal_error().