return null for collected and freed items during collection

style fix

Author: qunaibit

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/GcModuleBuiltins.java

@@ -180,7 +180,12 @@ static long javaCollect(Node inliningTarget, GilNode gil) {
             Runtime runtime = Runtime.getRuntime();
             long freeMemory = runtime.freeMemory();
             try {
-                CApiTransitions.ensurePollRefQueueCleanup();
+                PythonUtils.forceFullGC();
+                try {
+                    Thread.sleep(15);
+                } catch (InterruptedException e) {
+                    // doesn't matter, just trying to give the GC more time
+                }
             } finally {
                 gil.acquire();
             }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/cext/capi/CApiContext.java

@@ -42,6 +42,7 @@
 
 import static com.oracle.graal.python.PythonLanguage.CONTEXT_INSENSITIVE_SINGLETONS;
 import static com.oracle.graal.python.builtins.objects.cext.capi.PythonNativeWrapper.PythonAbstractObjectNativeWrapper.IMMORTAL_REFCNT;
+import static com.oracle.graal.python.builtins.objects.cext.capi.transitions.CApiTransitions.pollReferenceQueue;
 import static com.oracle.graal.python.nodes.SpecialAttributeNames.T___FILE__;
 import static com.oracle.graal.python.nodes.SpecialAttributeNames.T___LIBRARY__;
 import static com.oracle.graal.python.nodes.StringLiterals.J_LLVM_LANGUAGE;
@@ -713,7 +714,7 @@ public void triggerGC(PythonContext context, long size, Node caller) {
         for (int retries = 0; retries < MAX_COLLECTION_RETRIES; retries++) {
             delay += 50;
             doGc(delay);
-            CApiTransitions.pollReferenceQueue();
+            pollReferenceQueue();
             PythonContext.triggerAsyncActions(caller);
             if (allocatedMemory + size <= context.getOption(PythonOptions.MaxNativeMemory)) {
                 allocatedMemory += size;
@@ -958,12 +959,12 @@ public void exitCApiContext() {
              * deallocating objects may run arbitrary guest code that can again call into the
              * interpreter.
              */
-            CApiTransitions.ensurePollRefQueueCleanup();
+            pollReferenceQueue();
             PythonThreadState threadState = getContext().getThreadState(getContext().getLanguage());
             Object nativeThreadState = PThreadState.getNativeThreadState(threadState);
             if (nativeThreadState != null) {
                 PCallCapiFunction.callUncached(NativeCAPISymbol.FUN_PY_GC_COLLECT_NO_FAIL, nativeThreadState);
-                CApiTransitions.pollReferenceQueue();
+                pollReferenceQueue();
             }
             CApiTransitions.deallocateNativeWeakRefs(getContext());
         }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/cext/capi/transitions/CApiTransitions.java

@@ -103,7 +103,6 @@
 import com.oracle.graal.python.runtime.GilNode;
 import com.oracle.graal.python.runtime.PythonContext;
 import com.oracle.graal.python.runtime.PythonOptions;
-import com.oracle.graal.python.runtime.exception.PException;
 import com.oracle.graal.python.runtime.object.PythonObjectFactory;
 import com.oracle.graal.python.runtime.sequence.storage.NativeSequenceStorage;
 import com.oracle.graal.python.runtime.sequence.storage.SequenceStorage;
@@ -1506,11 +1505,19 @@ Object doNonWrapper(Object value,
                 int idx = readI32Node.read(HandlePointerConverter.pointerToStub(pointer), CFields.GraalPyObject__handle_table_index);
                 PythonObjectReference reference = nativeStubLookupGet(nativeContext, pointer, idx);
                 if (reference == null) {
+                    int collecting = readI32Node.read(pythonContext.getCApiContext().getGCState(), CFields.GCState__collecting);
+                    if (collecting == 1) {
+                        return PNone.NO_VALUE;
+                    }
                     CompilerDirectives.transferToInterpreterAndInvalidate();
                     throw CompilerDirectives.shouldNotReachHere("reference was freed: " + Long.toHexString(pointer));
                 }
                 wrapper = reference.get();
                 if (wrapper == null) {
+                    int collecting = readI32Node.read(pythonContext.getCApiContext().getGCState(), CFields.GCState__collecting);
+                    if (collecting == 1) {
+                        return PNone.NO_VALUE;
+                    }
                     CompilerDirectives.transferToInterpreterAndInvalidate();
                     throw CompilerDirectives.shouldNotReachHere("reference was collected: " + Long.toHexString(pointer));
                 }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/cext/structs/CFields.java

@@ -345,6 +345,7 @@ public enum CFields {
     GCState__debug(Int),
     GCState__generations(Pointer),
     GCState__generation0(Pointer),
+    GCState__collecting(Int),
 
     GCGeneration__count(Int),