vm: gracefully handle property setting on non-array, non-object values

Before this fix, the VM aborted due to an assert in libjson-c when an
attempt was made to set a property on a non-object value.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

2 files changed, 95 insertions, 1 deletions

diff --git a/tests/03_bugs/04_property_set_abort b/tests/03_bugs/04_property_set_abort
new file mode 100644
index 0000000..8af477f
--- /dev/null
+++ b/tests/03_bugs/04_property_set_abort
@@ -0,0 +1,76 @@
+When attempting to set a property on a non-array, non-object value the
+VM aborted due to an assert triggered by libjson-c.
+
+-- Testcase --
+{% (null).x = 1 %}
+-- End --
+
+-- Expect stderr --
+Type error: attempt to set property on null value
+In line 1, byte 15:
+
+ `{% (null).x = 1 %}`
+  Near here ----^
+
+
+-- End --
+
+
+-- Testcase --
+{% (1).x = 1 %}
+-- End --
+
+-- Expect stderr --
+Type error: attempt to set property on integer value
+In line 1, byte 12:
+
+ `{% (1).x = 1 %}`
+  Near here -^
+
+
+-- End --
+
+
+-- Testcase --
+{% (1.2).x = 1 %}
+-- End --
+
+-- Expect stderr --
+Type error: attempt to set property on double value
+In line 1, byte 14:
+
+ `{% (1.2).x = 1 %}`
+  Near here ---^
+
+
+-- End --
+
+
+-- Testcase --
+{% (true).x = 1 %}
+-- End --
+
+-- Expect stderr --
+Type error: attempt to set property on boolean value
+In line 1, byte 15:
+
+ `{% (true).x = 1 %}`
+  Near here ----^
+
+
+-- End --
+
+
+-- Testcase --
+{% ("test").x = 1 %}
+-- End --
+
+-- Expect stderr --
+Type error: attempt to set property on string value
+In line 1, byte 17:
+
+ `{% ("test").x = 1 %}`
+  Near here ------^
+
+
+-- End --
diff --git a/vm.c b/vm.c
index ca0435a..7fb7078 100644
--- a/vm.c
+++ b/vm.c
@@ -1096,7 +1096,25 @@ uc_vm_insn_store_val(uc_vm *vm, enum insn_type insn)
 	json_object *k = uc_vm_stack_pop(vm);
 	json_object *o = uc_vm_stack_pop(vm);
 
-	uc_vm_stack_push(vm, uc_setval(o, k, v));
+	const char *typenames[] = {
+		[json_type_string] = "string",
+		[json_type_int] = "integer",
+		[json_type_double] = "double",
+		[json_type_boolean] = "boolean",
+		[json_type_null] = "null"
+	};
+
+	switch (json_object_get_type(o)) {
+	case json_type_object:
+	case json_type_array:
+		uc_vm_stack_push(vm, uc_setval(o, k, v));
+		break;
+
+	default:
+		uc_vm_raise_exception(vm, EXCEPTION_TYPE,
+		                      "attempt to set property on %s value",
+		                      typenames[json_object_get_type(o)]);
+	}
 
 	uc_value_put(o);
 	uc_value_put(k);