The PyGC_* APIS are 3.10+ only; hide them behind #if

src/greenlet/greenlet_cpython_compat.hpp

@@ -11,6 +11,7 @@
 
 
 #if PY_VERSION_HEX >= 0x30A00B1
+#    define GREENLET_PY310 1
 /*
 Python 3.10 beta 1 changed tstate->use_tracing to a nested cframe member.
 See https://github.com/python/cpython/pull/25276
@@ -19,6 +20,7 @@ We have to save and restore this as well.
 #    define GREENLET_USE_CFRAME 1
 #else
 #    define GREENLET_USE_CFRAME 0
+#    define GREENLET_PY310 0
 #endif
 
 

src/greenlet/greenlet_greenlet.hpp

@@ -670,7 +670,9 @@ namespace greenlet
 
     // Instantiate one on the stack to save the GC state,
     // and then disable GC. When it goes out of scope, GC will be
-    // restored to its original state.
+    // restored to its original state. Sadly, these APIs are only
+    // available on 3.10+; luckily, we only need them on 3.11+.
+#if GREENLET_PY310
     class GCDisabledGuard
     {
     private:
@@ -689,6 +691,7 @@ namespace greenlet
             }
         }
     };
+#endif
 
 } // namespace greenlet ;