The symbols are a static array of NativeSymbol

typedef struct NativeSymbol {
    const char *symbol;
    void *func_ptr;
    const char *signature;
    /* attachment which can be retrieved in native API by
       calling wasm_runtime_get_function_attachment(exec_env) */
    void *attachment;
} NativeSymbol;

wasm_native_init

bool
wasm_native_init()
{
    NativeSymbol *native_symbols;
    uint32 n_native_symbols;

#if WASM_ENABLE_LIBC_BUILTIN != 0
    n_native_symbols = get_libc_builtin_export_apis(&native_symbols);
    if (!wasm_native_register_natives("env",
                                      native_symbols, n_native_symbols))
        return false;
#endif /* WASM_ENABLE_LIBC_BUILTIN */

#if WASM_ENABLE_SPEC_TEST
    n_native_symbols = get_spectest_export_apis(&native_symbols);
    if (!wasm_native_register_natives("spectest",
                                      native_symbols, n_native_symbols))
        return false;
#endif /* WASM_ENABLE_SPEC_TEST */

#if WASM_ENABLE_LIBC_WASI != 0
    n_native_symbols = get_libc_wasi_export_apis(&native_symbols);
    if (!wasm_native_register_natives("wasi_unstable",
                                      native_symbols, n_native_symbols))
        return false;
    if (!wasm_native_register_natives("wasi_snapshot_preview1",
                                      native_symbols, n_native_symbols))
        return false;
#endif

#if WASM_ENABLE_BASE_LIB != 0
    n_native_symbols = get_base_lib_export_apis(&native_symbols);
    if (n_native_symbols > 0
        && !wasm_native_register_natives("env",
                                         native_symbols, n_native_symbols))
        return false;
#endif

#if WASM_ENABLE_APP_FRAMEWORK != 0
    n_native_symbols = get_ext_lib_export_apis(&native_symbols);
    if (n_native_symbols > 0
        && !wasm_native_register_natives("env",
                                         native_symbols, n_native_symbols))
        return false;
#endif

#if WASM_ENABLE_LIB_PTHREAD != 0
    if (!lib_pthread_init())
        return false;

    n_native_symbols = get_lib_pthread_export_apis(&native_symbols);
    if (n_native_symbols > 0
        && !wasm_native_register_natives("env",
                                         native_symbols, n_native_symbols))
        return false;
#endif

#if WASM_ENABLE_LIBC_EMCC != 0
    n_native_symbols = get_libc_emcc_export_apis(&native_symbols);
    if (n_native_symbols > 0
        && !wasm_native_register_natives("env",
                                         native_symbols, n_native_symbols))
        return false;
#endif /* WASM_ENABLE_LIBC_EMCC */

    return true;
}

register_natives

Regestered functions are organized as a linked list, each module holds several functions imported from a specific library:

typedef struct NativeSymbolsNode {
    struct NativeSymbolsNode *next;
    const char *module_name;
    NativeSymbol *native_symbols;
    uint32 n_native_symbols;
    bool call_conv_raw;
} NativeSymbolsNode, *NativeSymbolsList;

static bool
register_natives(const char *module_name,
                 NativeSymbol *native_symbols,
                 uint32 n_native_symbols,
                 bool call_conv_raw)
{
    NativeSymbolsNode *node;
#if ENABLE_SORT_DEBUG != 0
    struct timeval start;
    struct timeval end;
    unsigned long timer;
#endif

    if (!(node = wasm_runtime_malloc(sizeof(NativeSymbolsNode))))
        return false;
#if WASM_ENABLE_MEMORY_TRACING != 0
    os_printf("Register native, size: %u\n", sizeof(NativeSymbolsNode));
#endif

    node->module_name = module_name;
    node->native_symbols = native_symbols;
    node->n_native_symbols = n_native_symbols;
    node->call_conv_raw = call_conv_raw;

    /* Add to list head */
    node->next = g_native_symbols_list;
    g_native_symbols_list = node;

#if ENABLE_SORT_DEBUG != 0
    gettimeofday(&start, NULL);
#endif

#if ENABLE_QUICKSORT == 0
    sort_symbol_ptr(native_symbols, n_native_symbols);
#else
    quick_sort_symbols(native_symbols, 0, (int)(n_native_symbols - 1));
#endif

#if ENABLE_SORT_DEBUG != 0
    gettimeofday(&end, NULL);
    timer = 1000000 * (end.tv_sec - start.tv_sec)
            + (end.tv_usec - start.tv_usec);
    LOG_ERROR("module_name: %s, nums: %d, sorted used: %ld us",
              module_name, n_native_symbols, timer);
#endif
    return true;
}