hakmem/core/box/free_path_stats_box.h

#ifndef HAKMEM_FREE_PATH_STATS_BOX_H
#define HAKMEM_FREE_PATH_STATS_BOX_H

#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>

typedef struct FreePathStats {
    uint64_t total_calls;

    uint64_t c7_ultra_fast;
    uint64_t smallheap_v3_fast;
    uint64_t smallheap_v6_fast;
    uint64_t tiny_heap_v1_fast;
    uint64_t pool_v1_fast;
    uint64_t remote_free;
    uint64_t super_lookup_called;
    uint64_t legacy_fallback;

    // Phase 4-1: Legacy per-class breakdown
    uint64_t legacy_by_class[8];  // C0-C7 の Legacy fallback 内訳
} FreePathStats;

// ENV gate
static inline bool free_path_stats_enabled(void) {
    static int g_enabled = -1;
    if (__builtin_expect(g_enabled == -1, 0)) {
        const char* e = getenv("HAKMEM_FREE_PATH_STATS");
        g_enabled = (e && *e && *e != '0') ? 1 : 0;
    }
    return g_enabled;
}

// Global stats instance
extern FreePathStats g_free_path_stats;

// Increment macros (with unlikely guard)
#define FREE_PATH_STAT_INC(field) \
    do { if (__builtin_expect(free_path_stats_enabled(), 0)) { \
        g_free_path_stats.field++; \
    } } while(0)

#endif // HAKMEM_FREE_PATH_STATS_BOX_H