1 files changed, 63 insertions, 0 deletions
diff --git a/sys/libc/cxwhen.c b/sys/libc/cxwhen.c
new file mode 100644
index 00000000..b3523dfe
--- /dev/null
+++ b/sys/libc/cxwhen.c
@@ -0,0 +1,63 @@
+/* Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+*/
+
+#define	import_spp
+#define	import_xnames
+#define	import_knames
+#define	import_libc
+#include <iraf.h>
+
+
+/* CXWHEN -- Post an exception handler.  The exception handler procedure
+** is called when an exception occurs, unless the exception has been
+** disabled.  If a user exception handler has not been posted and an
+** exception has not been disabled, a system default exception handler is
+** called when the exception occurs.
+**
+** Currently only four exceptions are recognized (import_xwhen):
+**
+**	X_INT		interrupt
+**	X_ARITH		arithmetic exception (e.g. divide by zero)
+**	X_ACV		access violation (e.g. illegal memory reference)
+**	X_IPC		write to IPC with no reader
+**
+** When an exception occurs the user supplied exception handler is called 
+** with the following argument list:
+**
+**	handler (&exception, &next_handler)
+**
+** The first argument is the code for the virtual exception calling the user
+** handler (the same handler may be posted for more than one exception).
+** The second argument is set by the user handler before exiting, and
+** must be either the ZLOCPR entry point address of the next exception
+** handler to be called or NULL, indicating that normal execution is to
+** resume.
+**
+** For portability reasons, only the virtual exceptions should be used to
+** post exception handlers.  For good diagnostic messages when an exception
+** occurs it is desirable, however, to have a more precise description of
+** the actual host system exception which occurred.  This may be obtained
+** by a call to C_XGMES.
+*/
+
+#define	SZ_ERRMSG	64
+typedef	int (*PFI)();		/* pointer to function returning int	*/
+
+
+/* C_XWHEN -- Post an exception handler for an exception, or disable the
+** exception (not all exceptions can be disabled).
+*/
+void
+c_xwhen (
+  int	exception,		/* code for virtual exception		*/
+  PFI	new_handler,		/* new exception handler		*/
+  PFI	*old_handler		/* old exception handler (output)	*/
+)
+{
+	XINT	excode = exception;
+	XINT	epa_new_handler = (XINT)new_handler;
+	XINT	epa_old_handler;
+
+	XWHEN (&excode, &epa_new_handler, &epa_old_handler);
+	*old_handler = (PFI)epa_old_handler;
+}