From bc8f9b2e5d84177b3a4fc5a86ef7d1a2a0ffa03a Mon Sep 17 00:00:00 2001
From: Florian Angerer <florian.angerer@oracle.com>
Date: Thu, 13 Oct 2022 11:51:39 +0200
Subject: [PATCH] Disallow specifying metaclass multiple times

---
 hpy/devel/src/runtime/ctx_type.c | 14 ++++++++++++--
 test/test_hpytype.py             | 24 ++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/hpy/devel/src/runtime/ctx_type.c b/hpy/devel/src/runtime/ctx_type.c
index cc803ec41..9cc2fa8f3 100644
--- a/hpy/devel/src/runtime/ctx_type.c
+++ b/hpy/devel/src/runtime/ctx_type.c
@@ -861,11 +861,16 @@ static PyObject *build_bases_from_params(HPyType_SpecParam *params)
 }
 
 _HPy_HIDDEN struct _typeobject *get_metatype(HPyType_SpecParam *params) {
+    struct _typeobject *res = NULL;
     if (params != NULL) {
         for (HPyType_SpecParam *p = params; p->kind != 0; p++) {
             switch (p->kind) {
                 case HPyType_SpecParam_Metaclass:
-                    return (struct _typeobject*) _h2py(p->object);
+                    if (res) {
+                        PyErr_SetString(PyExc_ValueError, "metaclass was specified multiple times");
+                        return NULL;
+                    }
+                    res = (struct _typeobject*) _h2py(p->object);
                     break;
                 default:
                     // other values are intentionally ignored
@@ -877,7 +882,7 @@ _HPy_HIDDEN struct _typeobject *get_metatype(HPyType_SpecParam *params) {
        has not explicitly been specified. We could default here to &PyType_Type
        but we actually want to use the bare 'PyType_FromSpecWithBases' if
        nothing was specified. */
-    return NULL;
+    return res;
 }
 
 static inline Py_ssize_t count_members(PyType_Spec *spec) {
@@ -1100,6 +1105,11 @@ ctx_Type_FromSpec(HPyContext *ctx, HPyType_Spec *hpyspec,
         return HPy_NULL;
     }
     struct _typeobject *metatype = get_metatype(params);
+    if (metatype == NULL && PyErr_Occurred()) {
+        PyMem_Free(spec->slots);
+        PyMem_Free(spec);
+        return HPy_NULL;
+    }
 
 #if HAVE_FROM_METACLASS
     /* On Python 3.12 an newer, we can just use 'PyType_FromMetaclass'. */
diff --git a/test/test_hpytype.py b/test/test_hpytype.py
index f35d86af1..9b429ea7b 100644
--- a/test/test_hpytype.py
+++ b/test/test_hpytype.py
@@ -995,6 +995,30 @@ class Sub(mod.Dummy):
             pass
         assert isinstance(Sub(), mod.Dummy)
 
+    def test_specparam_multiple_metaclass_fails(self):
+        import pytest
+        mod = self.make_module("""
+            static HPyType_Spec Dummy_spec = {
+                .name = "mytest.Dummy",
+            };
+            
+            HPyDef_METH(make_dummy, "make_dummy", make_dummy_impl, HPyFunc_NOARGS)
+            static HPy make_dummy_impl(HPyContext *ctx, HPy module)
+            {
+                HPyType_SpecParam param[] = {
+                    { HPyType_SpecParam_Metaclass, ctx->h_TypeType },
+                    { HPyType_SpecParam_Metaclass, ctx->h_LongType },
+                    { (HPyType_SpecParam_Kind)0 }
+                };
+                return HPyType_FromSpec(ctx, &Dummy_spec, param);
+            }
+            @EXPORT(make_dummy)
+            @INIT
+        """)
+
+        with pytest.raises(ValueError):
+            mod.make_dummy()
+
     def test_metaclass(self):
         import pytest
         mod = self.make_module("""