Ned Batchelder avatar Ned Batchelder committed 487cad9

Finished the trouble page. Closes issue #226.

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 .. _cover plug-in:  https://nose.readthedocs.org/en/latest/plugins/cover.html
 
 
+.. _contact:
+
 Getting help
 ------------
 
 .. _trouble:
 
-====================
-When things go wrong
-====================
+=========================
+Things that cause trouble
+=========================
 
-Coverage works pretty well, but occasionally things don't go as you would like.
-This page details problems, with links to coverage.py bug reports if
-appropriate.
+:history: 20121231T085200, brand new docs.
 
-You can of course search the `coverage.py bug tracker`_ directly to see if 
-there is some mention of your problem.
+Coverage works well, and I want it to properly measure any Python program, but
+there are some situations it can't cope with.  This page details some known
+problems, with possible courses of action, and links to coverage.py bug reports
+with more information.
+
+I would love to :ref:`hear from you <contact>` if you have information about any of
+these problems, even just to explain to me why you want them to start working
+properly.
+
+If your problem isn't discussed here, you can of course search the `coverage.py
+bug tracker`_ directly to see if there is some mention of it.
 
 .. _coverage.py bug tracker: https://bitbucket.org/ned/coveragepy/issues?status=new&status=open
 
 
-Kryptonite
-----------
+Things that don't work
+----------------------
 
-There are a number of popular packages that prevent coverage.py from working 
-properly.  
+There are a number of popular modules, packages, and libraries that prevent
+coverage.py from working properly:
 
-* gevent, `issue 149`_.
+* `execv`_, or one of its variants.  These end the current program and replace
+  it with a new one.  This doesn't save the collected coverage data, so your
+  program that calls execv will not be fully measured.  A patch for coverage.py
+  is in `issue 43`_.
 
-* execv, or one of its variants, `issue 43`_.
+* `multiprocessing`_ launches processes to provide parallelism.  These
+  processes don't get measured by coverage.py.  Some possible fixes are
+  discussed or linked to in `issue 117`_.
 
-* multiprocessing, `issue 117`_.
+* `gevent`_, which is based on `greenlet`_, and is similar to `eventlet`_. All
+  of these manipulate the C stack, and therefore confuse coverage.py.
+  `Issue 149`_ has some pointers to more information.
 
-Code is marked as not executed when I know it is.
+* `sys.settrace`_ is the Python feature that coverage.py uses to see what's
+  happening in your program.  If another part of your program is using
+  sys.settrace, then it will conflict with coverage.py, and it won't be
+  measured properly.
 
-link to DecoratorTools, TurboGears
-
-Try --timid
-
-psyco is an issue?
-
+.. _execv: http://docs.python.org/library/os#os.execl
+.. _multiprocessing: http://docs.python.org/library/multiprocessing.html
+.. _gevent: http://www.gevent.org/
+.. _greenlet: http://greenlet.readthedocs.org/
+.. _eventlet: http://eventlet.net/
+.. _sys.settrace: docs.python.org/library/sys.html#sys.settrace
 .. _issue 43: https://bitbucket.org/ned/coveragepy/issue/43/coverage-measurement-fails-on-code
 .. _issue 117: https://bitbucket.org/ned/coveragepy/issue/117/enable-coverage-measurement-of-code-run-by
 .. _issue 149: https://bitbucket.org/ned/coveragepy/issue/149/coverage-gevent-looks-broken
 
 
-Really obscure stuff
---------------------
+Things that require --timid
+---------------------------
+
+Some packages interfere with coverage measurement, but you might be able to
+make it work by using the ``--timid`` command-line switch, or the ``[run]
+timid=True`` configuration option.
+
+* `DecoratorTools`_, or any package which uses it, notably `TurboGears`_.
+  DecoratorTools fiddles with the trace function.  You  will need to use
+  ``--timid``.
+
+.. _DecoratorTools: http://pypi.python.org/pypi/DecoratorTools
+.. _TurboGears: http://turbogears.org/
+
+
+Really obscure things
+---------------------
 
 * Python 2.5 had a bug (`1569356`_) that could make your program behave
   differently when being measured with coverage.  This is diagnosed in `issue 51`_.
 
 .. _issue 51: http://bitbucket.org/ned/coveragepy/issue/51/turbogears-15-test-failing-with-coverage
 .. _1569356: http://bugs.python.org/issue1569356
+
+
+Still having trouble?
+---------------------
+
+If your problem isn't mentioned here, and isn't already reported in the `coverage.py bug tracker`_,
+please :ref:`get in touch with me <contact>`, we'll figure out a solution.
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