Issue #25401: Optimize bytes.fromhex() and bytearray.fromhex(): they are now
between 2x and 3.5x faster. Changes:
* Use a fast-path working on a char* string for ASCII string
* Use a slow-path for non-ASCII string
* Replace slow hex_digit_to_int() function with a O(1) lookup in
_PyLong_DigitValue precomputed table
* Use _PyBytesWriter API to handle the buffer
* Add unit tests to check the error position in error messages
Issue #25274: sys.setrecursionlimit() now raises a RecursionError if the new
recursion limit is too low depending at the current recursion depth. Modify
also the "lower-water mark" formula to make it monotonic. This mark is used to
decide when the overflowed flag of the thread state is reset.
sys.path has an unwritable __pycache__ directory.
This typically comes up when someone runs the test suite from an
administrative install of Python on Windows where the user does not
have write permissions to the stdlib's directory.
Thanks to Zachary Ware and Matthias Klose for reporting bugs related
to this issue.
(grafted from 34bbd537b3e688dfbb6498e9083445a6a72fc4b1)
sys.path has an unwritable __pycache__ directory.
This typically comes up when someone runs the test suite from an
administrative install of Python on Windows where the user does not
have write permissions to the stdlib's directory.
Thanks to Zachary Ware and Matthias Klose for reporting bugs related
to this issue.
* Thanks to the _PyBytesWriter API, output smaller than 512 bytes are allocated
on the stack and so avoid calling _PyBytes_Resize(). Because of that, change
the default buffer size to fmtcnt instead of fmtcnt+100.
* Rely on _PyBytesWriter algorithm to overallocate the buffer instead of using
a custom code. For example, _PyBytesWriter uses a different overallocation
factor (25% or 50%) depending on the platform to get best performances.
* Disable overallocation for the last write.
* Replace C loops to fill characters with memset()
* Add also many comments to _PyBytes_Format()
* Remove unused FORMATBUFLEN constant
* Avoid the creation of a temporary bytes object when formatting a floating
point number (when no custom formatting option is used)
* Fix also reference leaks on error handling
* Use Py_MEMCPY() to copy bytes between two formatters (%)
