Arena-Speicherallokation mit strikter Zeigerausrichtung

#include <stdio.h>
#include <stdint.h>
#include <stddef.h>
 
typedef struct {
    uint8_t *buffer;
    size_t capacity;
    size_t offset;
} Arena;
 
void *arena_alloc(Arena *arena, size_t size, size_t alignment) {
    uintptr_t current_ptr = (uintptr_t)(arena->buffer + arena->offset);
    uintptr_t aligned_ptr = (current_ptr + (alignment - 1)) & ~(alignment - 1);
    size_t padding = aligned_ptr - current_ptr;
 
    if (arena->offset + padding + size > arena->capacity) return NULL;
 
    arena->offset += padding + size;
    return (void *)aligned_ptr;
}
 
int main(void) {
    uint8_t memory_pool[1024];
    Arena arena = { .buffer = memory_pool, .capacity = sizeof(memory_pool), .offset = 0 };
 
    double *val = (double *)arena_alloc(&arena, sizeof(double), _Alignof(double));
    if (val) {
        *val = 3.14159;
        printf("Allocated aligned double: %f at %p\n", *val, (void *)val);
    }
    return 0;
}