New functions: at-exit-call and at-exit-do-not-call.

* sysif.c (at_exit_list): New static variable.
(at_exit_call, at_exit_do_not_call): New functions.
(at_exit_handler): New static function.
(sysif_init): GC-protect at_exit_list.
Register at_exit_handler with C atexit function.
Register intrinsic functions at-exit-call and
at-exit-do-not-call.

* sysif.h (at_exit_call, at_exit_do_not_call): Registered.

* txr.1: Documented.

1 files changed, 38 insertions, 0 deletions

diff --git a/txr.1 b/txr.1
index 7dd08b90..cb16a7f5 100644
--- a/txr.1
+++ b/txr.1
@@ -36279,6 +36279,44 @@ signal, known in \*(TX as the
 variable. Abnormal termination of the process is this signal's
 default action.
 
+.coNP Functions @ at-exit-call and @ at-exit-do-not-call
+.synb
+.mets (at-exit-call << function )
+.mets (at-exit-do-not-call << function )
+.syne
+.desc
+The
+.code at-exit-call
+function registers
+.meta function
+to be called when the process terminates normally.
+Multiple functions can be registered, and the same function
+can be registered more than once. The registered
+functions are called in reverse order of their
+registrations.
+
+The
+.code at-exit-do-not-call
+function removes all previous
+.code at-exit-call
+registrations of
+.metn function .
+
+The
+.code at-exit-call
+function returns
+.metn function .
+
+The
+.code at-exit-do-not-call
+function returns
+.code t
+if it removed anything,
+.code nil
+if no registrations of
+.meta function
+were found.
+
 .coNP Function @ usleep
 .synb
 .mets (usleep << usec )