Don't crash when assigning attributes of the GeneratorExit const singleton

Author: jepler

py/mpconfig.h

@@ -773,6 +773,16 @@ typedef long long mp_longint_impl_t;
 #define MICROPY_WARNINGS (0)
 #endif
 
+// Whether to support chained exceptions
+#ifndef MICROPY_CPYTHON_EXCEPTION_CHAIN
+#define MICROPY_CPYTHON_EXCEPTION_CHAIN (0)
+#endif
+
+// Whether the statically allocated GeneratorExit exception may be const
+#ifndef MICROPY_CONST_GENERATOREXIT_OBJ
+#define MICROPY_CONST_GENERATOREXIT_OBJ (!MICROPY_CPYTHON_EXCEPTION_CHAIN)
+#endif
+
 // Whether to support warning categories
 #ifndef MICROPY_WARNINGS_CATEGORY
 #define MICROPY_WARNINGS_CATEGORY (0)

py/obj.h

@@ -791,7 +791,9 @@ extern const struct _mp_obj_dict_t mp_const_empty_dict_obj;
 extern const struct _mp_obj_traceback_t mp_const_empty_traceback_obj;
 extern const struct _mp_obj_singleton_t mp_const_ellipsis_obj;
 extern const struct _mp_obj_singleton_t mp_const_notimplemented_obj;
-extern const struct _mp_obj_exception_t mp_const_GeneratorExit_obj;
+#if MICROPY_CONST_GENERATOREXIT_OBJ
+extern const struct _mp_obj_exception_t mp_static_GeneratorExit_obj;
+#endif
 
 // Fixed empty map. Useful when calling keyword-receiving functions
 // without any keywords from C, etc.

py/objexcept.c

@@ -218,9 +218,11 @@ void mp_obj_exception_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
     mp_obj_exception_t *self = MP_OBJ_TO_PTR(self_in);
     if (dest[0] != MP_OBJ_NULL) {
         // store/delete attribute
-        if (self == &mp_const_GeneratorExit_obj) {
+        #if MICROPY_CONST_GENERATOREXIT_OBJ
+        if (self == &mp_static_GeneratorExit_obj) {
             mp_raise_AttributeError(MP_ERROR_TEXT("can't set attribute"));
         }
+        #endif
         if (attr == MP_QSTR___traceback__) {
             if (dest[1] == mp_const_none) {
                 self->traceback = (mp_obj_traceback_t *)&mp_const_empty_traceback_obj;

py/objgenerator.c

@@ -38,7 +38,12 @@
 #include "supervisor/shared/translate/translate.h"
 
 // Instance of GeneratorExit exception - needed by generator.close()
-const mp_obj_exception_t mp_const_GeneratorExit_obj = {{&mp_type_GeneratorExit}, (mp_obj_tuple_t *)&mp_const_empty_tuple_obj, (mp_obj_traceback_t *)&mp_const_empty_traceback_obj};
+#if MICROPY_CONST_GENERATOREXIT_OBJ
+const
+#else
+static
+#endif
+mp_obj_exception_t mp_static_GeneratorExit_obj = {{&mp_type_GeneratorExit}, (mp_obj_tuple_t *)&mp_const_empty_tuple_obj, (mp_obj_traceback_t *)&mp_const_empty_traceback_obj};
 
 /******************************************************************************/
 /* generator wrapper                                                          */
@@ -362,9 +367,19 @@ STATIC mp_obj_t gen_instance_throw(size_t n_args, const mp_obj_t *args) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(gen_instance_throw_obj, 2, 4, gen_instance_throw);
 
+static mp_obj_t generatorexit(void) {
+    #if MICROPY_CPYTHON_EXCEPTION_CHAIN
+    MP_STATIC_ASSERT(!MICROPY_CONST_GENERATOREXIT_OBJ);
+    mp_static_GeneratorExit_obj.context = NULL;
+    mp_static_GeneratorExit_obj.cause = NULL;
+    mp_static_GeneratorExit_obj.suppress_context = false;
+    #endif
+    return MP_OBJ_FROM_PTR(&mp_static_GeneratorExit_obj);
+}
+
 STATIC mp_obj_t gen_instance_close(mp_obj_t self_in) {
     mp_obj_t ret;
-    switch (mp_obj_gen_resume(self_in, mp_const_none, MP_OBJ_FROM_PTR(&mp_const_GeneratorExit_obj), &ret)) {
+    switch (mp_obj_gen_resume(self_in, mp_const_none, generatorexit(), &ret)) {
         case MP_VM_RETURN_YIELD:
             mp_raise_msg(&mp_type_RuntimeError, MP_ERROR_TEXT("generator ignored GeneratorExit"));
 

py/vm.c

@@ -1391,7 +1391,10 @@ unwind_jump:;
             // - constant GeneratorExit object, because it's const
             // - exceptions re-raised by END_FINALLY
             // - exceptions re-raised explicitly by "raise"
-            if (nlr.ret_val != &mp_const_GeneratorExit_obj
+            if ( true
+                #if MICROPY_CONST_GENERATOREXIT_OBJ
+                && nlr.ret_val != &mp_static_GeneratorExit_obj
+                #endif
                 && *code_state->ip != MP_BC_END_FINALLY
                 && *code_state->ip != MP_BC_RAISE_LAST) {
                 const byte *ip = code_state->fun_bc->bytecode;