annotate contrib/win32/mercurial.ini @ 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.

; System-wide Mercurial config file.
;
; !!!  Do Not Edit This File !!!
;
; This file will be replaced by the installer on every upgrade.
; Editing this file can cause strange side effects on Vista.
;
; http://bitbucket.org/tortoisehg/stable/issue/135
;
; To change settings you see in this file, override (or enable) them in
; your user Mercurial.ini file, where USERNAME is your Windows user name:
;
; XP or older    - C:\Documents and Settings\USERNAME\Mercurial.ini
; Vista or later - C:\Users\USERNAME\Mercurial.ini


[ui]
; editor used to enter commit logs, etc.  Most text editors will work.
editor = notepad
; show changed files and be a bit more verbose if True
; verbose = True
 
; username data to appear in commits
; it usually takes the form: Joe User <[e-mail]>
; username = Joe User <[e-mail]>

; In order to push/pull over ssh you must specify an ssh tool
;ssh = "C:\Progra~1\TortoiseSVN\bin\TortoisePlink.exe" -ssh -2
;ssh = C:\cygwin\bin\ssh

;
; For more information about mercurial extensions, start here
; http://www.selenic.com/mercurial/wiki/index.cgi/UsingExtensions
;
; Extensions shipped with Mercurial
;
[extensions]
;acl =
;blackbox =
;bugzilla =
;children =
;churn =
;color =
;convert =
;eol =
;extdiff =
;fetch =
;gpg =
;hgcia =
;hgk =
;highlight = 
;histedit =
;interhg =
;largefiles =
;keyword =
;mq =
;notify =
;pager =
;patchbomb =
;progress =
;purge =
;rebase =
;record =
;relink =
;schemes =
;share =
;shelve =
;transplant =
;win32mbcs =
;zeroconf =

;
; Define external diff commands
;
[extdiff]
;cmd.bc3diff = C:\Program Files\Beyond Compare 3\BCompare.exe
;cmd.vdiff = C:\Progra~1\TortoiseSVN\bin\TortoiseMerge.exe
;cmd.vimdiff = gvim.exe
;opts.vimdiff = -f "+next" "+execute 'DirDiff' fnameescape(argv(0)) fnameescape(argv(1))"


[hgk]
; Replace the following with your path to hgk, uncomment it and 
; install ActiveTcl (or another win32 port like tclkit)
; path="C:\Program Files\Mercurial\Contrib\hgk.tcl"
; vdiff=vdiff
 

;
; The git extended diff format can represent binary files, file
; permission changes, and rename information that the normal patch format
; cannot describe.  However it is also not compatible with tools which
; expect normal patches. so enable git patches at your own risk.
;
[diff]
;git = false
;nodates = false