Use ANSI style comments for all generated code.

Cython/Utility/Buffer.c

@@ -162,7 +162,7 @@ static CYTHON_INLINE void __Pyx_SafeReleaseBuffer(Py_buffer* info);
 static const char* __Pyx_BufFmt_CheckString(__Pyx_BufFmt_Context* ctx, const char* ts);
 static void __Pyx_BufFmt_Init(__Pyx_BufFmt_Context* ctx,
                               __Pyx_BufFmt_StackElem* stack,
-                              __Pyx_TypeInfo* type); // PROTO
+                              __Pyx_TypeInfo* type); /* PROTO */
 
 
 /////////////// BufferFormatCheck ///////////////

Cython/Utility/Coroutine.c

@@ -139,7 +139,7 @@ static CYTHON_INLINE PyObject* __Pyx_Coroutine_AIter_Yield_From(__pyx_CoroutineO
 #if PY_VERSION_HEX < 0x030500B2
     if (!__Pyx_PyType_AsAsync(source)) {
         #ifdef __Pyx_Coroutine_USED
-        if (!__Pyx_Coroutine_CheckExact(source))  // quickly rule out a likely case
+        if (!__Pyx_Coroutine_CheckExact(source))  /* quickly rule out a likely case */
         #endif
         {
             // same as above in slow

Cython/Utility/ObjectHandling.c

@@ -1620,8 +1620,8 @@ done:
     Py_LeaveRecursiveCall();
     return result;
 }
-#endif  // CPython < 3.6
-#endif  // CYTHON_FAST_PYCALL
+#endif  /* CPython < 3.6 */
+#endif  /* CYTHON_FAST_PYCALL */
 
 
 /////////////// PyCFunctionFastCall.proto ///////////////
@@ -1652,7 +1652,7 @@ static CYTHON_INLINE PyObject * __Pyx_PyCFunction_FastCall(PyObject *func_obj, P
 
     return (*((__Pyx_PyCFunctionFast)meth)) (self, args, nargs, NULL);
 }
-#endif  // CYTHON_FAST_PYCCALL
+#endif  /* CYTHON_FAST_PYCCALL */
 
 
 /////////////// PyObjectCallOneArg.proto ///////////////

Cython/Utility/Overflow.c

@@ -265,7 +265,7 @@ static CYTHON_INLINE {{TYPE}} __Pyx_{{BINOP}}_{{NAME}}_checking_overflow({{TYPE}
             return __Pyx_{{BINOP}}_unsigned_long_long_checking_overflow(a, b, overflow);
 #endif
         } else {
-            abort(); return 0; // handled elsewhere
+            abort(); return 0; /* handled elsewhere */
         }
     } else {
         if (sizeof({{TYPE}}) == sizeof(int)) {
@@ -277,7 +277,7 @@ static CYTHON_INLINE {{TYPE}} __Pyx_{{BINOP}}_{{NAME}}_checking_overflow({{TYPE}
             return __Pyx_{{BINOP}}_long_long_checking_overflow(a, b, overflow);
 #endif
         } else {
-            abort(); return 0; // handled elsewhere
+            abort(); return 0; /* handled elsewhere */
         }
     }
 }