From 6bc75ea5118dd2808cb4801d3c4e3b279df93992 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Sat, 20 Jun 2020 12:23:14 -0700
Subject: exit: argument becomes optional

* sysif.c (exit_wrap): Check for missing status argument, and
map to EXIT_SUCCESS.
(sysif_init): Register exit as having optional argument.

* txr.1: Update documentation regarding optional argument of
exit.  Also, EXIT_SUCCESS and EXIT_FAILURE are no longer
mentioned, only that t maps to succes and nil to failure.
---
 sysif.c |  6 ++++--
 txr.1   | 24 +++++++++++++-----------
 2 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/sysif.c b/sysif.c
index 7c55ffed..e54d6c5f 100644
--- a/sysif.c
+++ b/sysif.c
@@ -173,7 +173,9 @@ static val exit_wrap(val status)
 {
   int stat;
 
-  if (status == nil)
+  if missingp(status)
+    stat = EXIT_SUCCESS;
+  else if (status == nil)
     stat = EXIT_FAILURE;
   else if (status == t)
     stat = EXIT_SUCCESS;
@@ -2348,7 +2350,7 @@ void sysif_init(void)
 
   reg_fun(intern(lit("errno"), user_package), func_n1o(errno_wrap, 0));
   reg_fun(intern(lit("strerror"), user_package), func_n1o(strerror_wrap, 0));
-  reg_fun(intern(lit("exit"), user_package), func_n1(exit_wrap));
+  reg_fun(intern(lit("exit"), user_package), func_n1o(exit_wrap, 0));
   reg_fun(intern(lit("at-exit-call"), user_package), func_n1(at_exit_call));
   reg_fun(intern(lit("at-exit-do-not-call"), user_package), func_n1(at_exit_do_not_call));
   reg_fun(intern(lit("abort"), user_package), func_n0(abort_wrap));
diff --git a/txr.1 b/txr.1
index 0e8dba44..597c0723 100644
--- a/txr.1
+++ b/txr.1
@@ -58603,28 +58603,30 @@ If the host platform fails to provide a description, the function returns
 
 .coNP Function @ exit
 .synb
-.mets (exit << status )
+.mets (exit <> [ status ])
 .syne
 .desc
 The
 .code exit
 function terminates the entire process (running \*(TX image), specifying
-the termination status to the operating system. Values of
+the termination status to the operating system. Values of the optional
 .meta status
-may be
+parameter may be
 .codn nil ,
 .codn t ,
 or an integer value.  The value
 .code nil
-corresponds to the C constant
-.codn EXIT_FAILURE ,
-and
+indicates an unsuccessful termination status, whereas
 .code t
-corresponds to
-.codn EXIT_SUCCESS .
-These are platform-independent
-indicators of failed or successful termination. The numeric value 0 also
-indicates success.
+indicates a successful termination status.
+An absence of the
+.meta status
+argument also specifies a successful termination status.
+If
+.meta status
+is an integer value, it specifies a successful termination if it is
+.code 0
+otherwise the interpretation of the value is platform specific.
 
 .coNP Variables @, e2big @, eacces @, eaddrinuse @, eaddrnotavail @, eafnosupport @, eagain @, ealready @, ebadf @, ebadmsg @, ebusy @, ecanceled @, echild @, econnaborted @, econnrefused @, econnreset @, edeadlk @, edestaddrreq @, edom @, edquot @, eexist @, efault @, efbig @, ehostunreach @, eidrm @, eilseq @, einprogress @, eintr @, einval @, eio @, eisconn @, eisdir @, eloop @, emfile @, emlink @, emsgsize @, emultihop @, enametoolong @, enetdown @, enetreset @, enetunreach @, enfile @, enobufs @, enodata @, enodev @, enoent @, enoexec @, enolck @, enolink @, enomem @, enomsg @, enoprotoopt @, enospc @, enosr @, enostr @, enosys @, enotconn @, enotdir @, enotempty @, enotrecoverable @, enotsock @, enotsup @, enotty @, enxio @, eopnotsupp @, eoverflow @, eownerdead @, eperm @, epipe @, eproto @, eprotonosupport @, eprototype @, erange @, erofs @, espipe @, esrch @, estale @, etime @, etimedout @, etxtbsy @ ewouldblock and @ exdev
 .desc
-- 
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