[issue36085] Enable better DLL resolution

[Eryk Sun]

Eryk Sun <eryksun at gmail.com> added the comment:

> Since I just dug enough to find it, the best way to diagnose problems 
> with dependent DLLs not being found is probably to run Process Monitor 
> [1] while doing the import and checking its logs. It should show the 
> paths that were attempted to be accessed.

Don't forget loader snaps, which we can log using a standard debugger such as WinDbg or by attaching a Python script as a debugger (e.g. debug a child process via the DEBUG_PROCESS creation flag). For the latter, we need a debug-event loop (i.e. WaitForDebugEventEx via ctypes) that logs debug-string events. This will show the paths that the loader checks and the load attempts that fail with STATUS_DLL_NOT_FOUND (0xC0000135). We have to first enable loader snaps for the executable by setting a flag value of 2 in the "GlobalFlag" DWORD in the key "HKLM\Software\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\<executable name>". Or use gflags.exe to set this value.

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<https://bugs.python.org/issue36085>
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