ctypes maintains thread-local storage that has space for two error
numbers: private copies of the system 'errno' value and, on Windows,
the system error code accessed by the GetLastError() and
SetLastError() api functions.
Foreign functions created with CDLL(..., use_errno=True), when called,
swap the system 'errno' value with the private copy just before the
actual function call, and swapped again immediately afterwards. The
'use_errno' parameter defaults to False, in this case 'ctypes_errno'
is not touched.
On Windows, foreign functions created with CDLL(...,
use_last_error=True) or WinDLL(..., use_last_error=True) swap the
system LastError value with the ctypes private copy.
The values are also swapped immeditately before and after ctypes
callback functions are called, if the callbacks are constructed using
the new optional use_errno parameter set to True: CFUNCTYPE(...,
use_errno=TRUE) or WINFUNCTYPE(..., use_errno=True).
New ctypes functions are provided to access the ctypes private copies
from Python:
- ctypes.set_errno(value) and ctypes.set_last_error(value) store
'value' in the private copy and returns the previous value.
- ctypes.get_errno() and ctypes.get_last_error() returns the current
ctypes private copies value.
convention that allows safe access to errno)
This code does not yet work on OS X (__thread storage specifier not
available), so i needs a configure check plus a more portable
solution.
errno (and LastError, on Windows).
ctypes maintains a module-global, but thread-local, variable that
contains an error number; called 'ctypes_errno' for this discussion.
This variable is a private copy of the systems 'errno' value; the copy
is swapped with the 'errno' variable on several occasions.
Foreign functions created with CDLL(..., use_errno=True), when called,
swap the values just before the actual function call, and swapped
again immediately afterwards. The 'use_errno' parameter defaults to
False, in this case 'ctypes_errno' is not touched.
The values are also swapped immeditately before and after ctypes
callback functions are called, if the callbacks are constructed using
the new optional use_errno parameter set to True: CFUNCTYPE(..., use_errno=TRUE)
or WINFUNCTYPE(..., use_errno=True).
Two new ctypes functions are provided to access the 'ctypes_errno'
value from Python:
- ctypes.set_errno(value) sets ctypes_errno to 'value', the previous
ctypes_errno value is returned.
- ctypes.get_errno() returns the current ctypes_errno value.
---
On Windows, the same scheme is implemented for the error value which
is managed by the GetLastError() and SetLastError() windows api calls.
The ctypes functions are 'ctypes.set_last_error(value)' and
'ctypes.get_last_error()', the CDLL and WinDLL optional parameter is
named 'use_last_error', defaults to False.
---
On Windows, TlsSetValue and TlsGetValue calls are used to provide
thread local storage for the variables; ctypes compiled with __GNUC__
uses __thread variables.
The exact behaviour of omitted and negative indices for the Pointer type may
need a closer look (especially as it's subtly different from simple slices)
but there's time yet before 2.6, and not enough before 3.0a1 :-)
Python would crash instead of raising an error.
The crash was caused by a section of code that should have been
removed long ago, at that time ctypes had other ways to pass
parameters to function calls.
Check this and raise an error when something else is used - before
this change ctypes would hang or crash when such a callback was
called. This is a partial fix for #1574584.
Will backport to release25-maint.
of the Python part of a callback function to C. If it cannot be
converted, call PyErr_WriteUnraisable with the exception we got.
Before, arbitrary data has been passed to the calling C code in this
case.
(I'm not really sure the NEWS entry is understandable, but I cannot
find better words)
ctypes instances no longer have the internal and undocumented
'_as_parameter_' attribute which was used to adapt them to foreign
function calls; this mechanism is replaced by a function pointer in
the type's stgdict.
In the 'from_param' class methods, try the _as_parameter_ attribute if
other conversions are not possible.
This makes the documented _as_parameter_ mechanism work as intended.
Change the ctypes version number to 1.0.1.
Thomas Heller
Christian Heimes
Thomas Wouters
Neal Norwitz
Brett Cannon