Avoid triggering type-check assert for cyfuncs [0.29.x] (#5031)

* Avoid triggering type-check assert for cyfuncs
* Make some jobs run with debug assertions

Co-authored-by: Stefano Rivera <github@rivera.za.net>

Cython/Utility/ObjectHandling.c

@@ -2321,7 +2321,10 @@ static CYTHON_INLINE PyObject* __Pyx_PyObject_CallNoArg(PyObject *func) {
         return __Pyx_PyFunction_FastCall(func, NULL, 0);
     }
 #endif
-#ifdef __Pyx_CyFunction_USED
+#if defined(__Pyx_CyFunction_USED) && defined(NDEBUG)
+    // TODO PyCFunction_GET_FLAGS has a type-check assert that breaks with a CyFunction
+    // in debug mode. There is likely to be a better way of avoiding tripping this
+    // check that doesn't involve disabling the optimized path.
     if (likely(PyCFunction_Check(func) || __Pyx_CyFunction_Check(func)))
 #else
     if (likely(PyCFunction_Check(func)))

Tools/ci-run.sh

@@ -109,6 +109,16 @@ export PATH="/usr/lib/ccache:$PATH"
 # to override the previous ones, so '-O0 -O3' == '-O3'
 # This is true for the latest msvc, gcc and clang
 CFLAGS="-O0 -ggdb -Wall -Wextra"
+# Trying to cover debug assertions in the CI without adding
+# extra jobs. Therefore, odd-numbered minor versions of Python
+# running C++ jobs get NDEBUG undefined, and even-numbered
+# versions running C jobs get NDEBUG undefined.
+ODD_VERSION=$(python3 -c "import sys; print(sys.version_info[1]%2)")
+if [[ $BACKEND == *"cpp"* && $ODD_VERSION == "1" ]]; then
+    CFLAGS="$CFLAGS -UNDEBUG"
+elif [[ $ODD_VERSION == "0" ]]; then
+    CFLAGS="$CFLAGS -UNDEBUG"
+fi
 
 if [[ $NO_CYTHON_COMPILE != "1" && $PYTHON_VERSION != "pypy"* ]]; then