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This commit adds the errno attribute to exceptions, so code can retrieve errno codes from an OSError using exc.errno. The implementation here simply lets `errno` (and the existing `value`) attributes work on any exception instance (they both alias args[0]). This is for efficiency and to keep code size down. The pros and cons of this are: Pros: - more compatible with CPython, less difference to document and learn - OSError().errno will correctly return None, whereas the current way of doing it via OSError().args[0] will raise an IndexError - it reduces code size on most bare-metal ports (because they already have the errno qstr) - for Python code that uses exc.errno the generated bytecode is 2 bytes smaller and more efficient to execute (compared with exc.args[0]); so bytecode loaded to RAM saves 2 bytes RAM for each use of this attribute, and bytecode that is frozen saves 2 bytes flash/ROM for each use - it's easier/shorter to type, and saves 2 bytes of space in .py files that use it (for each use) Cons: - increases code size by 4-8 bytes on minimal ports that don't already have the `errno` qstr - all exceptions now have .errno and .value attributes (a cpydiff test is added to address this) See also #2407. Signed-off-by: Damien George <damien@micropython.org>
35 lines
1004 B
ReStructuredText
35 lines
1004 B
ReStructuredText
:mod:`uerrno` -- system error codes
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===================================
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.. module:: uerrno
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:synopsis: system error codes
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|see_cpython_module| :mod:`python:errno`.
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This module provides access to symbolic error codes for `OSError` exception.
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A particular inventory of codes depends on :term:`MicroPython port`.
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Constants
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---------
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.. data:: EEXIST, EAGAIN, etc.
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Error codes, based on ANSI C/POSIX standard. All error codes start with
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"E". As mentioned above, inventory of the codes depends on
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:term:`MicroPython port`. Errors are usually accessible as ``exc.errno``
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where ``exc`` is an instance of `OSError`. Usage example::
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try:
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uos.mkdir("my_dir")
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except OSError as exc:
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if exc.errno == uerrno.EEXIST:
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print("Directory already exists")
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.. data:: errorcode
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Dictionary mapping numeric error codes to strings with symbolic error
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code (see above)::
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>>> print(uerrno.errorcode[uerrno.EEXIST])
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EEXIST
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