Cython modules not automatically rebuild through setup.py on changes of pxd files

After some frustrating hours I discovered that if you use a distutils setup.py script to create a cython module the module is not updated if you only change a pxd header file. Especially in a bigger project with many cython modules this can be easily forgotten, so in case of unexpected behaviour just try removing all pyd files so everything will be build fresh.

It is perhaps even saver to touch all .pyx files because if you remove the pyd file the .c file is not necessarily recreated!

cython -mno-cygwin problems

The command I use to compile a cython extension on windows:

python setup.py build_ext --inplace --compiler=mingw32

(see also these two posts) has problems with newer mingw/cygwin installations. Already for some to the compiler option -mno-cygwin is no longer used and the mingw compiler should be called directly. When you run the setup.py script with the compiler flag as shown, however, python automatically adds the -mno-cygwin flag. This then stops the compiler. The best solution for this I have found so far is to change the

c:\Python27\Lib\distutils\cygwinccompiler.py

file. Simply remove the -mno-cygwin option everywhere in the definition of the Mingw32CCompiler class (just search for no-cygwin in this file and you will find it).

Looks like I also could have googled this instead of finding out again how to use grep to search in subdirectories which is not as simple as adding the -r option ( find ./* -type f -exec grep -l "no-cygwin" {} \;).