Critical section for thread safety

[hasumikin]

est_set_critical_section() to register callbacks for wrapping critical section provided by the platform.

Example for pico-sdk:

#include <pico/critical_section.h>

static critical_section_t heap_critsec;

static void heap_enter_critical(void)
{
  critical_section_enter_blocking(&heap_critsec);
}

static void heap_exit_critical(void)
{
  critical_section_exit(&heap_critsec);
}

int main(void)
{
  ESTALLOC *est = est_init(mem, bytes);
  critical_section_init(&heap_critsec); // from pico-sdk
  est_set_critical_section(est, heap_enter_critical, heap_exit_critical);
}

[Copilot]

Pull request overview

Adds optional platform-provided critical section callbacks to make the allocator’s core operations thread-safe on embedded targets (e.g., by disabling interrupts or acquiring a lock) without hard-coding a specific RTOS/SDK dependency.

Changes:

• Extend ESTALLOC with enter_critical / exit_critical callback pointers and expose est_set_critical_section() to register them.
• Wrap allocator operations (malloc/permalloc/free/realloc and statistics collection) with enter/exit critical section hooks.
• Add a few additional internal assertions to detect heap corruption cases earlier.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
estalloc.h	Adds critical section callbacks to ESTALLOC and declares est_set_critical_section() API.
estalloc.c	Implements callback registration and applies critical section wrapping to allocator operations.

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