Reintroduce workaround for C++ destructors calling Py_DECREF

Author: msimacek

graalpython/com.oracle.graal.python.cext/src/capi.c

@@ -849,6 +849,22 @@ PyAPI_FUNC(void) initialize_graal_capi(TruffleEnv* env, void* (*getBuiltin)(int
     PyTruffle_Log(PY_TRUFFLE_LOG_FINE, "initialize_graal_capi: %fs", ((double) (clock() - t)) / CLOCKS_PER_SEC);
 }
 
+/*
+This is a workaround for C++ modules, namely PyTorch, that declare global/static variables with destructors that call
+_Py_DECREF. The destructors get called by libc during exit during which we cannot make upcalls as that would segfault.
+So we rebind them to no-ops when exiting.
+*/
+Py_ssize_t nop_GraalPy_get_PyObject_ob_refcnt(PyObject* obj) {
+ return 100; // large dummy refcount
+}
+void nop_GraalPy_set_PyObject_ob_refcnt(PyObject* obj, Py_ssize_t refcnt) {
+ // do nothing
+}
+PyAPI_FUNC(void) finalizeCAPI() {
+ GraalPy_get_PyObject_ob_refcnt = nop_GraalPy_get_PyObject_ob_refcnt;
+ GraalPy_set_PyObject_ob_refcnt = nop_GraalPy_set_PyObject_ob_refcnt;
+}
+
 static void unimplemented(const char* name) {
 	printf("Function not implemented in GraalPy: %s\n", name);
 }

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

@@ -187,7 +187,6 @@ private record ClosureInfo(Object closure, Object delegate, Object executable, l
      */
     private final HashMap<Object, ClosureInfo> callableClosureByExecutable = new HashMap<>();
     private final HashMap<Long, ClosureInfo> callableClosures = new HashMap<>();
-    private Object nativeLibrary;
 
     /**
      * This list holds a strong reference to all loaded extension libraries to keep the library
@@ -591,11 +590,11 @@ public static CApiContext ensureCapiWasLoaded(Node node, PythonContext context,
 
     @TruffleBoundary
     public void finalizeCapi() {
-        if (nativeLibrary != null) {
+        if (useNativeBackend && getLLVMLibrary() != null) {
             try {
-                Object initFunction = InteropLibrary.getUncached().readMember(nativeLibrary, "finalizeCAPI");
+                Object finalizeFunction = InteropLibrary.getUncached().readMember(getLLVMLibrary(), "finalizeCAPI");
                 Object signature = PythonContext.get(null).getEnv().parseInternal(Source.newBuilder(J_NFI_LANGUAGE, "():VOID", "exec").build()).call();
-                SignatureLibrary.getUncached().call(signature, initFunction);
+                SignatureLibrary.getUncached().call(signature, finalizeFunction);
             } catch (InteropException e) {
                 throw CompilerDirectives.shouldNotReachHere(e);
             }