18 Flags and Hooks
The following flags and hooks are available when Racket is
scheme_exit — This pointer can be set to a function
that takes an integer argument and returns void; the function
will be used as the default exit handler. The default is NULL.
scheme_make_stderr, — These pointers can be set to a
function that takes no arguments and returns a Racket port
Scheme_Object * to be used as the starting standard input,
output, and/or error port. The defaults are NULL. Setting the
initial error port is particularly important for seeing unexpected
error messages if stderr output goes nowhere.
scheme_console_output — This pointer can be set to a
function that takes a string and a intptr_t string length; the
function will be called to display internal Racket warnings and
messages that possibly contain non-terminating nuls. The default is
scheme_check_for_break — This points to a function
of no arguments that returns an integer. It is used as the default
user-break polling procedure in the main thread. A non-zero return
value indicates a user break, and each time the function returns a
non-zero value, it counts as a new break signal (though the break
signal may be ignored if a previous signal is still pending). The
default is NULL.
scheme_case_sensitive — If this flag is set to a
non-zero value before scheme_basic_env is called, then
Racket will not ignore capitalization for symbols and global
variable names. The value of this flag should not change once it is
set. The default is zero.
scheme_allow_set_undefined — This flag determines
the initial value of compile-allow-set!-undefined. The default
scheme_console_printf — This function pointer was
left for backward compatibility. The default builds a string and
The function calls scheme_seal_parameters automatically.
Takes a snapshot of the current values of built-in parameters. These
values are used for privileged actions, such as installing a PLaneT