5.3.14 Cython: Dealing with weird build errors

Problem: You get an error like this

%skip
...
lude/python2.5 -c sage/modules/complex_double_vector.c 
      -o build/temp.macosx-10.3-i386-2.5/sage/modules/complex_double_vector.o -w
sage/modules/complex_double_vector.c:366: 
       error: field '__pyx_base' has incomplete type
sage/modules/complex_double_vector.c:373: 
       error: field '__pyx_base' has incomplete type
error: command 'gcc' failed with exit status 1
sage: There was an error installing modified sage library code.

Solution: In this case I added cimport sage.structure.element to complex_double_vector.pxd and the problem disappeared. In general, look at the generated C file to see what type is incomplete (i.e., not properly declared), then add an explicit cimport to your pxd file (or top of your pyx file if you don't have a pxd file).

Problem: Errors such as "XXX does not appear to be the correct type object".
Solution: This can happen when the build system doesn't properly detect a dependency and regenerate the corresponding files. If you know which .pyx file should be recompiled, just touch it. If you don't, you can always type sage -ba to brutally rebuild everything, which will take about 3-5 minutes.

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