Global state and env::set_current_dir

[aws]

@worik

What is “SetCurrentDirectory”?

From MSDN

Multithreaded applications and shared library code should not use the SetCurrentDirectory function and should avoid using relative path names. The current directory state written by the SetCurrentDirectory function is stored as a global variable in each process, therefore multithreaded applications cannot reliably use this value without possible data corruption from other threads that may also be reading or setting this value. This limitation also applies to the GetCurrentDirectory and GetFullPathName functions. The exception being when the application is guaranteed to be running in a single thread, for example parsing file names from the command line argument string in the main thread prior to creating any additional threads. Using relative path names in multithreaded applications or shared library code can yield unpredictable results and is not supported.

The Win32 API is interesting like this.

When writing a lot of C/C++ code over the last few years I ran into this. As retep said, it's thread-safe, it's just that your results aren't. This is contrast to the process models on other operating systems where if you manipulate the environment it acts sort of like container/process->threads->userland magic tiering; Windows treats threads almost like a process (somewhat arbitrarily). The model works for some things, and has drawbacks for others.