From b02f03c979cda37e43828cd6e1787649f1d8ca8c Mon Sep 17 00:00:00 2001 From: Steve Vinoski Date: Tue, 22 Feb 2011 18:07:57 -0500 Subject: add support for checking if an ERL_NIF_TERM is an exception Add the enif_is_exception function to allow callers to determine whether an ERL_NIF_TERM represents an exception. (Currently the only supported exception is badarg since only enif_make_badarg exists, but this will likely be expanded in future releases.) This allows NIF code to call other NIF functions that return ERL_NIF_TERM and properly check to see if the returned terms are exceptions. Without the enif_is_exception function, developers have to create their own means of checking whether a function creates an exception, such as returning boolean success/failure indicators or some other special value indicating that an exception is in effect. The declaration of enif_is_exception in erl_nif_api_funcs.h respects the order of declarations required to keep compatibility on Windows. Add a new test to verify the operation of enif_is_exception. Modify the erl_nif man page to add a description of enif_is_exception and also to clarify the requirements of calling the enif_make_badarg function. If code calls enif_make_badarg, the env passed in gets set with exception information and so the return value of the calling function MUST be the badarg term returned from enif_make_badarg. Also clarify that the result of enif_make_badarg may be passed only to enif_is_exception and not to any other NIF API functions. --- erts/emulator/beam/erl_nif.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'erts/emulator/beam/erl_nif.c') diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c index 135c6b0ccc..8b48444904 100644 --- a/erts/emulator/beam/erl_nif.c +++ b/erts/emulator/beam/erl_nif.c @@ -430,6 +430,11 @@ int enif_is_list(ErlNifEnv* env, ERL_NIF_TERM term) return is_list(term) || is_nil(term); } +int enif_is_exception(ErlNifEnv* env, ERL_NIF_TERM term) +{ + return term == THE_NON_VALUE; +} + static void aligned_binary_dtor(struct enif_tmp_obj_t* obj) { erts_free_aligned_binary_bytes_extra((byte*)obj,ERTS_ALC_T_TMP); -- cgit v1.2.3