These test fails with C++ on Cygwin due to lack of long double functions. This was not a problem in plain C, but the C++ compiler is stricter about undeclared functions.  Better to skip them anyways.

os.rename() could fail sometimes with a permission error; using shutil.move() instead seems to be more robust against that.

see
https://mail.python.org/pipermail/cython-devel/2016-April/004776.html

Also note better support for gcc variants that are not named 'gcc' exactly.

Right now this is the only such test. There are other tests that generate code that uses long double math functions, but not in a way that appears to break the test.

This issue is particular to Cygwin since on Cygwin distutils.spawn uses os.fork(). Deleting DLLs can lead to Cygwin's fork() breaking, due to trying to load a DLL that no longer exists.  This means that the test run will use a little more disk space on Cygwin, but still allows full (or partial) cleanup at the end.

See https://mail.python.org/pipermail/cython-devel/2016-April/004777.html

Fix declarations and callingconvention tests to not incorrectly use DL_IMPORT when building the module

See https://github.com/cython/cython/pull/360#issuecomment-214420624

Python3