Add a debug helper test that prints information about the current C build environment.

tests/compile/buildenv.pyx

+"""
+Non-test that prints debug information about the current build environment.
+"""
+
+from __future__ import print_function
+
+import sys
+
+cdef extern from *:
+    # Python runtime
+    cdef long PY_VERSION_HEX
+
+    # Cython config
+    cdef int CYTHON_COMPILING_IN_CPYTHON
+    cdef int CYTHON_COMPILING_IN_PYPY
+    cdef int CYTHON_COMPILING_IN_PYSTON
+    cdef int CYTHON_USE_PYLONG_INTERNALS
+    cdef int CYTHON_USE_PYLIST_INTERNALS
+    cdef int CYTHON_USE_UNICODE_INTERNALS
+    cdef int CYTHON_USE_UNICODE_WRITER
+    cdef int CYTHON_AVOID_BORROWED_REFS
+    cdef int CYTHON_ASSUME_SAFE_MACROS
+    cdef int CYTHON_UNPACK_METHODS
+    cdef int CYTHON_FAST_THREAD_STATE
+    cdef int CYTHON_FAST_PYCALL
+    cdef int CYTHON_PEP489_MULTI_PHASE_INIT
+    cdef int CYTHON_USE_TP_FINALIZE
+
+    # C and platform specifics
+    cdef int SIZEOF_INT
+    cdef int SIZEOF_LONG
+    cdef int SIZEOF_SIZE_T
+    cdef int SIZEOF_LONG_LONG
+    cdef int SIZEOF_VOID_P
+
+    # PyLong internals
+    cdef long PyLong_BASE
+    cdef long PyLong_MASK
+    cdef int PyLong_SHIFT
+    cdef int digit
+    cdef int sdigit
+
+
+print(f"""Python build environment:
+Python  {sys.version_info}
+PY_VERSION_HEX  0x{PY_VERSION_HEX:X}
+
+CYTHON_COMPILING_IN_CPYTHON  {CYTHON_COMPILING_IN_CPYTHON}
+CYTHON_COMPILING_IN_PYPY  {CYTHON_COMPILING_IN_PYPY}
+CYTHON_COMPILING_IN_PYSTON  {CYTHON_COMPILING_IN_PYSTON}
+
+CYTHON_USE_PYLONG_INTERNALS  {CYTHON_USE_PYLONG_INTERNALS}
+CYTHON_USE_PYLIST_INTERNALS  {CYTHON_USE_PYLIST_INTERNALS}
+CYTHON_USE_UNICODE_INTERNALS  {CYTHON_USE_UNICODE_INTERNALS}
+CYTHON_USE_UNICODE_WRITER  {CYTHON_USE_UNICODE_WRITER}
+CYTHON_AVOID_BORROWED_REFS  {CYTHON_AVOID_BORROWED_REFS}
+CYTHON_ASSUME_SAFE_MACROS  {CYTHON_ASSUME_SAFE_MACROS}
+CYTHON_UNPACK_METHODS  {CYTHON_UNPACK_METHODS}
+CYTHON_FAST_THREAD_STATE  {CYTHON_FAST_THREAD_STATE}
+CYTHON_FAST_PYCALL  {CYTHON_FAST_PYCALL}
+CYTHON_PEP489_MULTI_PHASE_INIT  {CYTHON_PEP489_MULTI_PHASE_INIT}
+CYTHON_USE_TP_FINALIZE  {CYTHON_USE_TP_FINALIZE}
+
+PyLong_BASE  0x{PyLong_BASE:X}
+PyLong_MASK  {PyLong_MASK:X}
+PyLong_SHIFT  {PyLong_SHIFT}
+sizeof(digit)  {sizeof(digit)}
+sizeof(sdigit)  {sizeof(sdigit)}
+
+SIZEOF_INT  {SIZEOF_INT}  ({sizeof(int)})
+SIZEOF_LONG  {SIZEOF_LONG}  ({sizeof(long)})
+SIZEOF_SIZE_T  {SIZEOF_SIZE_T}  ({sizeof(Py_ssize_t)}, {getattr(sys, 'maxsize', getattr(sys, 'maxint', None))})
+SIZEOF_LONG_LONG  {SIZEOF_LONG_LONG}  ({sizeof(long long)})
+SIZEOF_VOID_P  {SIZEOF_VOID_P}  ({sizeof(void*)})
+""")