There are some specific versions of Guile’s original
with-throw-handler exception-handling primitives that are still
widely used in C code.
take Scheme procedures as body and handler arguments.
scm_internal_catch are equivalents taking
body is called as
body (body_data) with a catch
on exceptions of the given tag type. If an exception is caught,
pre_unwind_handler and handler are called as
handler (handler_data, key, args).
key and args are the
SCM key and argument list from
body and handler should have the following prototypes.
scm_t_catch_handler are pointer
typedefs for these.
SCM body (void *data); SCM handler (void *data, SCM key, SCM args);
The body_data and handler_data parameters are passed to the respective calls so an application can communicate extra information to those functions.
If the data consists of an
SCM object, care should be taken that
it isn’t garbage collected while still required. If the
SCM is a
local C variable, one way to protect it is to pass a pointer to that
variable as the data parameter, since the C compiler will then know the
value must be held on the stack. Another way is to use
scm_remember_upto_here_1 (see Foreign Object Memory Management).
scm_with_throw_handler takes Scheme procedures as body
(thunk) and handler arguments.
scm_c_with_throw_handler is an
equivalent taking C functions. See
(see Exceptions and C) for a description of the parameters, the
behaviour however of course follows