Phase v4-3.1: reuse C7 v4 pages and record prep calls

core/box/smallobject_cold_iface_v4.h

@@ -0,0 +1,21 @@
+// smallobject_cold_iface_v4.h - SmallObject HotHeap v4 Cold Interface (境界 API のみ)
+//
+// 役割:
+//   - HotBox_v4 と Superslab/Warm/Remote を繋ぐ関数ポインタの箱を定義する。
+//   - 実装は後続フェーズで追加し、いまは型と宣言だけを置く。
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "smallobject_hotbox_v4_box.h"
+
+typedef struct SmallColdIfaceV4 {
+    small_page_v4* (*refill_page)(small_heap_ctx_v4*, uint32_t class_idx);
+    void (*retire_page)(small_heap_ctx_v4*, uint32_t class_idx, small_page_v4* page);
+    bool (*remote_push)(small_page_v4* page, void* ptr, uint32_t self_tid);
+    void (*remote_drain)(small_heap_ctx_v4*);
+} SmallColdIfaceV4;
+
+// Cold iface accessor（実装は後続フェーズ）
+const SmallColdIfaceV4* small_cold_iface_v4_get(void);

core/box/smallobject_hotbox_v4_box.h

@@ -0,0 +1,48 @@
+// smallobject_hotbox_v4_box.h - SmallObject HotHeap v4 (型スケルトン)
+//
+// 役割:
+//   - v4 のページ / クラス / TLS コンテキスト型と API 宣言だけを定義する箱。
+//   - 挙動はまだ v3/v1 のまま。alloc/free 本体は後続フェーズで実装する。
+#pragma once
+
+#include <stdint.h>
+#include <stddef.h>
+
+#include "tiny_geometry_box.h"
+
+#ifndef SMALLOBJECT_NUM_CLASSES
+#define SMALLOBJECT_NUM_CLASSES TINY_NUM_CLASSES
+#endif
+
+// Page metadata for v4 HotBox
+typedef struct small_page_v4 {
+    void* freelist;
+    uint16_t used;
+    uint16_t capacity;
+    uint8_t class_idx;
+    uint8_t flags;
+    uint32_t block_size;
+    uint8_t* base;
+    void* slab_ref;  // Superslab / lease token (box境界で扱う)
+    struct small_page_v4* next;
+} small_page_v4;
+
+// Per-class heap state (current / partial / full lists)
+typedef struct small_class_heap_v4 {
+    small_page_v4* current;
+    small_page_v4* partial_head;
+    small_page_v4* full_head;
+    uint32_t partial_count;
+} small_class_heap_v4;
+
+// TLS heap context (per-thread)
+typedef struct small_heap_ctx_v4 {
+    small_class_heap_v4 cls[SMALLOBJECT_NUM_CLASSES];
+} small_heap_ctx_v4;
+
+// TLS accessor (実装は後続フェーズで追加)
+small_heap_ctx_v4* small_heap_ctx_v4_get(void);
+
+// Hot path API (C7-only stub; later phases will expand)
+void* small_heap_alloc_fast_v4(small_heap_ctx_v4* ctx, int class_idx);
+void small_heap_free_fast_v4(small_heap_ctx_v4* ctx, int class_idx, void* ptr);

core/box/smallobject_hotbox_v4_env_box.h

@@ -0,0 +1,45 @@
+// smallobject_hotbox_v4_env_box.h - ENV gate for SmallObject HotHeap v4
+// デフォルト: OFF（研究用に明示 opt-in）
+#pragma once
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "../hakmem_tiny_config.h"
+
+static inline int small_heap_v4_enabled(void) {
+    static int g_enable = -1;
+    if (__builtin_expect(g_enable == -1, 0)) {
+        const char* e = getenv("HAKMEM_SMALL_HEAP_V4_ENABLED");
+        if (e && *e) {
+            g_enable = (*e != '0') ? 1 : 0;
+        } else {
+            // v4 は研究箱。明示しない限り OFF
+            g_enable = 0;
+        }
+    }
+    return g_enable;
+}
+
+static inline int small_heap_v4_class_enabled(uint8_t class_idx) {
+    static int g_parsed = 0;
+    static unsigned g_mask = 0;
+    if (__builtin_expect(!g_parsed, 0)) {
+        const char* e = getenv("HAKMEM_SMALL_HEAP_V4_CLASSES");
+        if (e && *e) {
+            unsigned v = (unsigned)strtoul(e, NULL, 0);
+            g_mask = v & 0xFFu;
+        } else {
+            // デフォルトは全クラス OFF
+            g_mask = 0;
+        }
+        g_parsed = 1;
+    }
+    if (!small_heap_v4_enabled()) return 0;
+    if (class_idx >= TINY_NUM_CLASSES) return 0;
+    return (g_mask & (1u << class_idx)) != 0;
+}
+
+static inline int small_heap_v4_c7_enabled(void) {
+    return small_heap_v4_class_enabled(7);
+}

core/box/tiny_route_env_box.h

@@ -10,12 +10,14 @@
 #include "tiny_heap_env_box.h"
 
 #include "smallobject_hotbox_v3_env_box.h"
+#include "smallobject_hotbox_v4_env_box.h"
 
 typedef enum {
     TINY_ROUTE_LEGACY = 0,
     TINY_ROUTE_HEAP = 1,             // TinyHeap v1
     TINY_ROUTE_HOTHEAP_V2 = 2,       // TinyHotHeap v2
     TINY_ROUTE_SMALL_HEAP_V3 = 3,    // SmallObject HotHeap v3 (C7-first,研究箱)
+    TINY_ROUTE_SMALL_HEAP_V4 = 4,    // SmallObject HotHeap v4 (stub, route未使用)
 } tiny_route_kind_t;
 
 extern tiny_route_kind_t g_tiny_route_class[TINY_NUM_CLASSES];
@@ -23,7 +25,9 @@ extern int g_tiny_route_snapshot_done;
 
 static inline void tiny_route_snapshot_init(void) {
     for (int i = 0; i < TINY_NUM_CLASSES; i++) {
-        if (small_heap_v3_class_enabled((uint8_t)i)) {
+        if (small_heap_v4_class_enabled((uint8_t)i)) {
+            g_tiny_route_class[i] = TINY_ROUTE_SMALL_HEAP_V4;
+        } else if (small_heap_v3_class_enabled((uint8_t)i)) {
             g_tiny_route_class[i] = TINY_ROUTE_SMALL_HEAP_V3;
         } else if (tiny_hotheap_v2_class_enabled((uint8_t)i)) {
             g_tiny_route_class[i] = TINY_ROUTE_HOTHEAP_V2;
@@ -47,7 +51,10 @@ static inline tiny_route_kind_t tiny_route_for_class(uint8_t ci) {
 }
 
 static inline int tiny_route_is_heap_kind(tiny_route_kind_t route) {
-    return route == TINY_ROUTE_HEAP || route == TINY_ROUTE_HOTHEAP_V2 || route == TINY_ROUTE_SMALL_HEAP_V3;
+    return route == TINY_ROUTE_HEAP ||
+           route == TINY_ROUTE_HOTHEAP_V2 ||
+           route == TINY_ROUTE_SMALL_HEAP_V3 ||
+           route == TINY_ROUTE_SMALL_HEAP_V4;
 }
 
 // C7 front が TinyHeap を使うか（Route snapshot 経由で判定）