feat: rebuild heap4 card around upstream FreeRTOS allocator

src/tasks/task01_first_fit_split.c

@@ -0,0 +1,72 @@
+#include "heap4_model.h"
+
+enum {
+    ARENA_BYTES = 256,
+    REQUEST_BYTES = 13,
+    WANTED_BYTES = (sizeof(ModelBlock) + REQUEST_BYTES + 7U) & ~7U
+};
+
+typedef struct {
+    ModelBlock allocated;
+    uint8_t payload[WANTED_BYTES - sizeof(ModelBlock)];
+    ModelBlock remainder;
+    uint8_t free_payload[ARENA_BYTES - WANTED_BYTES - sizeof(ModelBlock)];
+} SplitArena;
+
+typedef union {
+    uint64_t force_alignment;
+    SplitArena blocks;
+} AlignedSplitArena;
+
+AlignedSplitArena g_split_arena;
+ModelBlock *g_free_head;
+volatile size_t g_header_bytes;
+volatile size_t g_wanted_bytes;
+volatile size_t g_remainder_bytes;
+volatile size_t g_payload_offset;
+volatile int g_split_addresses_aligned;
+volatile int g_task01_pass;
+
+__attribute__((noinline)) void task01_debug_checkpoint(void)
+{
+#if defined(__GNUC__)
+    __asm__ volatile("" ::: "memory");
+#endif
+}
+
+int main(void)
+{
+    SplitArena *arena = &g_split_arena.blocks;
+    uintptr_t base = (uintptr_t)&arena->allocated;
+    uintptr_t remainder = (uintptr_t)&arena->remainder;
+
+    arena->allocated.next = NULL;
+    arena->allocated.size = WANTED_BYTES;
+    arena->remainder.next = NULL;
+    arena->remainder.size = ARENA_BYTES - WANTED_BYTES;
+    arena->payload[0] = (uint8_t)'A';
+    g_free_head = &arena->remainder;
+
+    g_header_bytes = sizeof(ModelBlock);
+    g_wanted_bytes = WANTED_BYTES;
+    g_remainder_bytes = arena->remainder.size;
+    g_payload_offset = (size_t)((uintptr_t)&arena->payload[0] - base);
+    g_split_addresses_aligned =
+        (base % MODEL_ALIGNMENT) == 0U &&
+        (remainder % MODEL_ALIGNMENT) == 0U;
+    g_task01_pass =
+        g_wanted_bytes == model_align_up(sizeof(ModelBlock) + REQUEST_BYTES) &&
+        (size_t)(remainder - base) == g_wanted_bytes &&
+        g_remainder_bytes + g_wanted_bytes == ARENA_BYTES &&
+        g_payload_offset == sizeof(ModelBlock) &&
+        g_split_addresses_aligned;
+
+    task01_debug_checkpoint();
+
+#if defined(HOST_PRINTF)
+    printf("header=%zu wanted=%zu remainder=%zu payload=%zu aligned=%d pass=%d\n",
+           g_header_bytes, g_wanted_bytes, g_remainder_bytes,
+           g_payload_offset, g_split_addresses_aligned, g_task01_pass);
+#endif
+    return g_task01_pass ? 0 : 1;
+}