add libc building to agbcc.

1 files changed, 80 insertions, 0 deletions

diff --git a/libc/stdlib/atexit.c b/libc/stdlib/atexit.c
new file mode 100644
index 0000000..02375af
--- /dev/null
+++ b/libc/stdlib/atexit.c
@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 1990 Regents of the University of California.
+ * All rights reserved.
+ *
+ * %sccs.include.redist.c%
+ */
+
+/*
+FUNCTION
+<<atexit>>---request execution of functions at program exit
+
+INDEX
+	atexit
+
+ANSI_SYNOPSIS
+	#include <stdlib.h>
+	int atexit(void (*<[function]>)(void);
+
+TRAD_SYNOPSIS
+	#include <stdlib.h>
+	int atexit((<[function]>)
+	void (*<[function]>)();
+
+DESCRIPTION
+You can use <<atexit>> to enroll functions in a list of functions that
+will be called when your program terminates normally.  The argument is
+a pointer to a user-defined function (which must not require arguments and
+must not return a result).
+
+The functions are kept in a LIFO stack; that is, the last function
+enrolled by <<atexit>> will be the first to execute when your program
+exits.
+
+There is no built-in limit to the number of functions you can enroll
+in this list; however, after every group of 32 functions is enrolled,
+<<atexit>> will call <<malloc>> to get space for the next part of the
+list.   The initial list of 32 functions is statically allocated, so
+you can always count on at least that many slots available.
+
+RETURNS
+<<atexit>> returns <<0>> if it succeeds in enrolling your function,
+<<-1>> if it fails (possible only if no space was available for
+<<malloc>> to extend the list of functions).
+
+PORTABILITY
+<<atexit>> is required by the ANSI standard, which also specifies that
+implementations must support enrolling at least 32 functions.
+
+Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
+<<lseek>>, <<read>>, <<sbrk>>, <<write>>.
+*/
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <reent.h>
+
+/*
+ * Register a function to be performed at exit.
+ */
+
+int
+_DEFUN (atexit,
+	(fn),
+	_VOID _EXFUN ((*fn), (_VOID)))
+{
+  register struct _atexit *p;
+
+  if ((p = _REENT->_atexit) == NULL)
+    _REENT->_atexit = p = &_REENT->_atexit0;
+  if (p->_ind >= _ATEXIT_SIZE)
+    {
+      if ((p = (struct _atexit *) malloc (sizeof *p)) == NULL)
+	return -1;
+      p->_ind = 0;
+      p->_next = _REENT->_atexit;
+      _REENT->_atexit = p;
+    }
+  p->_fns[p->_ind++] = fn;
+  return 0;
+}