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/test/nif_SUITE_data/nif_SUITE.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'erts/emulator/test/nif_SUITE_data/nif_SUITE.c') diff --git a/erts/emulator/test/nif_SUITE_data/nif_SUITE.c b/erts/emulator/test/nif_SUITE_data/nif_SUITE.c index 8489124966..dc047394b5 100644 --- a/erts/emulator/test/nif_SUITE_data/nif_SUITE.c +++ b/erts/emulator/test/nif_SUITE_data/nif_SUITE.c @@ -801,6 +801,23 @@ static ERL_NIF_TERM check_is(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[] return ok_atom; } +/* + * no arguments + * + * This function is separate from check_is because it calls enif_make_badarg + * and so it must return the badarg exception as its return value. Thus, the + * badarg exception indicates success. Failure is indicated by returning an + * error atom. + */ +static ERL_NIF_TERM check_is_exception(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]) +{ + ERL_NIF_TERM error_atom = enif_make_atom(env, "error"); + ERL_NIF_TERM badarg = enif_make_badarg(env); + if (enif_is_exception(env, error_atom)) return error_atom; + if (!enif_is_exception(env, badarg)) return error_atom; + return badarg; +} + /* * argv[0] atom with length of 6 * argv[1] list with length of 6 @@ -1383,6 +1400,7 @@ static ErlNifFunc nif_funcs[] = {"last_resource_dtor_call", 0, last_resource_dtor_call}, {"make_new_resource", 2, make_new_resource}, {"check_is", 10, check_is}, + {"check_is_exception", 0, check_is_exception}, {"length_test", 5, length_test}, {"make_atoms", 0, make_atoms}, {"make_strings", 0, make_strings}, -- cgit v1.2.3