Message 67508 - Python tracker (original) (raw)

Ok, here is the plan (basically Armin's proposal):

ctypes maintains a gloabl, but thread-local, variable that contains an error number; called 'ctypes_errno' for this discussion.

ctypes.set_errno(value) copies 'value' into ctypes_errno, and returns the old value. ctypes.get_errno() returns the current ctypes_errno value.

Foreign functions created with CDLL(..., use_errno=True), when called, copy the ctypes_errno value into the real errno just before they are called, and copy the real errno value into ctypes_errno. The 'use_errno' parameter defaults to False, in this case ctypes_errno is not touched.

The same scheme is implemented on Windows for GetLastError() and SetLastError(), the variable is named 'ctypes_LastError', and the CDLL and WinDLL optional parameter is named 'use_LastError', and also defaults to False.

Armin Rigo schrieb:

(Another note: the C-level errno and the TLS copy should also be synchronized when the C code invokes a Python callback.)

Not sure what this is for, please proofread the patch when I attach one. Even better, someone could supply test-cases for all this, either as executable code or as prosa.

(A related issue that we may or may not care about: it's more than likely that various people have already come up with various workarounds to handle errno, and these workarounds will probably stop working after ctypes is changed...)

Since the new behaviour will only be invoked when use_errno or use_LastError is used, they should be able to still use their workarounds.