Mercurial > hg
view contrib/win32/ReadMe.html @ 20742:3681de20b0a7
parsers: fail fast if Python has wrong minor version (issue4110)
This change causes an informative ImportError to be raised when importing
the parsers extension module if the minor version of the currently-running
Python interpreter doesn't match that of the Python used when compiling
the extension module.
This change also exposes a parsers.versionerrortext constant in the
C implementation of the module. Its presence can be used to determine
whether this behavior is present in a version of the module. The value
of the constant is the leading text of the ImportError raised and is set
to "Python minor version mismatch".
Here is an example of what the new error looks like:
Traceback (most recent call last):
File "test.py", line 1, in <module>
import mercurial.parsers
ImportError: Python minor version mismatch: The Mercurial extension
modules were compiled with Python 2.7.6, but Mercurial is currently using
Python with sys.hexversion=33883888: Python 2.5.6
(r256:88840, Nov 18 2012, 05:37:10)
[GCC 4.2.1 Compatible Apple Clang 4.1 ((tags/Apple/clang-421.11.66))]
at: /opt/local/Library/Frameworks/Python.framework/Versions/2.5/Resources/
Python.app/Contents/MacOS/Python
The reason for raising an error in this scenario is that Python's C API
is known not to be compatible from minor version to minor version, even
if sys.api_version is the same. See for example this Python bug report
about incompatibilities between 2.5 and 2.6+:
http://bugs.python.org/issue8118
These incompatibilities can cause Mercurial to break in mysterious,
unforeseen ways. For example, when Mercurial compiled with Python 2.7 was
run with 2.5, the following crash occurred when running "hg status":
http://bz.selenic.com/show_bug.cgi?id=4110
After this crash was fixed, running with Python 2.5 no longer crashes, but
the following puzzling behavior still occurs:
$ hg status
...
File ".../mercurial/changelog.py", line 123, in __init__
revlog.revlog.__init__(self, opener, "00changelog.i")
File ".../mercurial/revlog.py", line 251, in __init__
d = self._io.parseindex(i, self._inline)
File ".../mercurial/revlog.py", line 158, in parseindex
index, cache = parsers.parse_index2(data, inline)
TypeError: data is not a string
which can be reproduced more simply with:
import mercurial.parsers as parsers
parsers.parse_index2("", True)
Both the crash and the TypeError occurred because the Python C API's
PyString_Check() returns the wrong value when the C header files from
Python 2.7 are run with Python 2.5. This is an example of an
incompatibility of the sort mentioned in the Python bug report above.
Failing fast with an informative error message results in a better user
experience in cases like the above. The information in the ImportError
also simplifies troubleshooting for those on Mercurial mailing lists, the
bug tracker, etc.
This patch only adds the version check to parsers.c, which is sufficient
to affect command-line commands like "hg status" and "hg summary".
An idea for a future improvement is to move the version-checking C code
to a more central location, and have it run when importing all
Mercurial extension modules and not just parsers.c.
author | Chris Jerdonek <chris.jerdonek@gmail.com> |
---|---|
date | Wed, 04 Dec 2013 20:38:27 -0800 |
parents | 9c963a43ecfb |
children | 8fe5fc8d7b8e |
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>Mercurial for Windows</title> <meta http-equiv="Content-Type" content="text/html;charset=utf-8" > <style type="text/css"> <!-- html { font-family: sans-serif; margin: 1em 2em; } p { margin-top: 0.5em; margin-bottom: 0.5em; } pre { margin: 0.25em 0em; padding: 0.5em; background-color: #EEE; border: thin solid #CCC; } .indented { padding-left: 10pt; } --> </style> </head> <body> <h1>Mercurial for Windows</h1> <p>Welcome to Mercurial for Windows!</p> <p> Mercurial is a command-line application. You must run it from the Windows command prompt (or if you're hard core, a <a href="http://www.mingw.org/">MinGW</a> shell). </p> <p class="indented"> <i>Note: the standard <a href="http://www.mingw.org/">MinGW</a> msys startup script uses rxvt which has problems setting up standard input and output. Running bash directly works correctly.</i> </p> <p> For documentation, please visit the <a href="http://mercurial.selenic.com/">Mercurial web site</a>. You can also download a free book, <a href="http://hgbook.red-bean.com/">Mercurial: The Definitive Guide</a>. </p> <p> By default, Mercurial installs to <tt>C:\Program Files\Mercurial</tt>. The Mercurial command is called <tt>hg.exe</tt>. </p> <h1>Testing Mercurial after you've installed it</h1> <p> The easiest way to check that Mercurial is installed properly is to just type the following at the command prompt: </p> <pre> hg </pre> <p> This command should print a useful help message. If it does, other Mercurial commands should work fine for you. </p> <h1>Configuration notes</h1> <h4>Default editor</h4> <p> The default editor for commit messages is 'notepad'. You can set the <tt>EDITOR</tt> (or <tt>HGEDITOR</tt>) environment variable to specify your preference or set it in <tt>mercurial.ini</tt>: </p> <pre> [ui] editor = whatever </pre> <h4>Configuring a Merge program</h4> <p> It should be emphasized that Mercurial by itself doesn't attempt to do a Merge at the file level, neither does it make any attempt to Resolve the conflicts. </p> <p> By default, Mercurial will use the merge program defined by the <tt>HGMERGE</tt> environment variable, or uses the one defined in the <tt>mercurial.ini</tt> file. (see <a href="http://mercurial.selenic.com/wiki/MergeProgram">MergeProgram</a> on the Mercurial Wiki for more information) </p> <h1>Reporting problems</h1> <p> Before you report any problems, please consult the <a href="http://mercurial.selenic.com/">Mercurial web site</a> and see if your question is already in our list of <a href="http://mercurial.selenic.com/wiki/FAQ">Frequently Answered Questions</a> (the "FAQ"). </p> <p> If you cannot find an answer to your question, please feel free to send mail to the Mercurial mailing list, at <a href="mailto:mercurial@selenic.com">mercurial@selenic.com</a>. <b>Remember</b>, the more useful information you include in your report, the easier it will be for us to help you! </p> <p> If you are IRC-savvy, that's usually the fastest way to get help. Go to <tt>#mercurial</tt> on <tt>irc.freenode.net</tt>. </p> <h1>Author and copyright information</h1> <p> Mercurial was written by <a href="http://www.selenic.com">Matt Mackall</a>, and is maintained by Matt and a team of volunteers. </p> <p> The Windows installer was written by <a href="http://www.serpentine.com/blog">Bryan O'Sullivan</a>. </p> <p> Mercurial is Copyright 2005-2014 Matt Mackall and others. See the <tt>Contributors.txt</tt> file for a list of contributors. </p> <p> Mercurial is free software; you can redistribute it and/or modify it under the terms of the <a href="http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt">GNU General Public License version 2</a> or any later version. </p> <p> Mercurial is distributed in the hope that it will be useful, but <b>without any warranty</b>; without even the implied warranty of <b>merchantability</b> or <b>fitness for a particular purpose</b>. See the GNU General Public License for more details. </p> </body> </html>