hakmem/core/box/wrapper_env_box.c

#define _GNU_SOURCE
#include "wrapper_env_box.h"
#include <stdlib.h>
#include <string.h>

wrapper_env_cfg_t g_wrapper_env = {.inited = 0, .step_trace = 0, .ld_safe_mode = 1, .free_wrap_trace = 0, .wrap_diag = 0};

static inline int env_flag(const char* name, int def) {
    const char* e = getenv(name);
    if (!e || *e == '\0') return def;
    return (*e != '0');
}

static inline int env_int(const char* name, int def) {
    const char* e = getenv(name);
    if (!e || *e == '\0') return def;
    char* end;
    long val = strtol(e, &end, 10);
    return (end != e) ? (int)val : def;
}

void wrapper_env_init_once(void) {
    // Atomic CAS to ensure exactly-once initialization
    static _Atomic int init_started = 0;
    int expected = 0;

    if (!atomic_compare_exchange_strong_explicit(&init_started, &expected, 1,
                                                  memory_order_acq_rel,
                                                  memory_order_relaxed)) {
        // Someone else is initializing or already initialized
        // Spin until they're done
        while (!__builtin_expect(g_wrapper_env.inited, 1)) {
            __builtin_ia32_pause();
        }
        return;
    }

    // We own the initialization
    g_wrapper_env.step_trace      = env_flag("HAKMEM_STEP_TRACE", 0);
    g_wrapper_env.ld_safe_mode    = env_int("HAKMEM_LD_SAFE", 1);
    g_wrapper_env.free_wrap_trace = env_flag("HAKMEM_FREE_WRAP_TRACE", 0);
    g_wrapper_env.wrap_diag       = env_flag("HAKMEM_WRAP_DIAG", 0);

    // Mark as initialized last with memory barrier
    atomic_store_explicit(&g_wrapper_env.inited, 1, memory_order_release);
}

__attribute__((constructor(101)))
static void wrapper_env_ctor(void) {
    // Constructor priority 101 runs early (libc uses 100+)
    // This ensures initialization before any malloc calls
    if (!g_wrapper_env.inited) {
        wrapper_env_init_once();
    }
}