PY_ARRAY_UNIQUE_SYMBOL must be set to a unique value
for each extension module. But, you actually don't need to set it at all
unless you are going to compile an extension module that uses two
different source files
If your extension module is contained in a single source file then you
can get rid of extmodule.h entirely and replace the first part of
Debugging C Extensions on Windows¶
Debugging C extensions on Windows can be tricky. If you compile your
extension code in debug mode, you have to link against the debug version
of the Python library, e.g.
Python24_d.lib. When building with
Visual Studio, this is taken care of by a pragma in
you force the compiler to link debug code against the release library,
you will probably get the following errors (especially when compiling
SWIG wrapped codes):
However, now you also need a debug build of the Python interpreter if you want to import this debuggable extension module. Now you also need debug builds of every other extension module you use. Clearly, this can take some time to get sorted out.
An alternative is to build your library code as a debug DLL. This way, you can at least that your extension module is passing the right data to the library code you are wrapping.
As an aside, it seems that the MinGW GCC compiler doesn't produce debug symbols that are understood by the Visual Studio debugger.
To develop a stable extension module, it is essential that you check the memory allocation and memory accesses done by your C code. On Linux, you can use Valgrind. On Windows, you could try a commercial tool such as Rational PurifyPlus.
Before using Valgrind, make sure your extension module is compiled with
-g switch to GCC so that you can get useful stack traces when
errors are detected.
Then put the following in a shell script, say
valgrind-python.supp suppresses some warnings caused by the Python code. You can find the suppression file for Python 2.4 in the Python SVN repository. See also README.valgrind in the same location. Some of the suppressions are commented out by default. Enable them by removing the # comment markers.
chmod +x valgrind_py.sh and run it as
- Extending and Embedding the Python Interpreter (read this first)
- Python/C API Reference Manual (then browse through this)
- Chapter 13 of Guide to NumPy describes the complete API
- Chapter 14 deals with extending !NumPy (make sure you have the edition dated March 15, 2006 or later)
Mailing List Threads¶
Section author: AlbertStrasheim, TravisOliphant, DavidLinke