升级 Xcode 16 之后 g_rootDir 丢失

[zrqSimon]

在做 Xcode 16 适配过程中发现，执行 initializeMMKV 后 g_rootDir 是正常有值的，但是在执行 MMKV *MMKV::mmkvWithID(const string &mmapID, MMKVMode mode, string *cryptKey, MMKVPath_t *rootPath) 时 g_rootDir 就被置为空串，导致后续的读写操作都失败了。
mmkv 版本：1.2.16

[lingol]

There's not much place for assigning g_rootDir. Can you set a breakpoint to see when & where exactly it's set with empty?

[lingol]

NO, I don't need any of these global var initialization info.

[lingol]

You are not getting it. Only the stacks when it's set with empty after it's set with non-empty is meaningful.

[zrqSimon]

The stack trace suggests that g_rootDir was initially assigned a value, but then the default initialization method for the string class was called, effectively setting g_rootDir to an empty string.
Is that correct?

[zrqSimon]

old value -> new value

[lingol]

No, it's a wrong order. A global var's __cxx_global_var_init should be called once and only once.
Check if you have embedded MMKV.framework multiple times in different modules/frameworks/so.

[lingol]

Oh, I just noticed that you init mmkv by some +load method. Looks like it's invoked before the g_rootDir's own initialization function __cxx_global_var_init.
Never do that.
Move to the didFinishLuanching as we suggested in the doc/wiki.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // init MMKV in the main thread
    [MMKV initializeMMKV:nil];

    //...
    return YES;
}

[zrqSimon]

it works. thanks!
by the way. i don't have this issue on Xcode 15. Do you know of any changes in Xcode 16 that would affect the call timing of __cxx_global_var_init?

[lingol]

Ask Apple.