scc

commit 33b9f7476c6f730def0034b2b36ad14dde30d2f2
parent 3ddba6b6ed93c63e246397e08acdc39a2e1744a9
Author: Roberto E. Vargas Caballero <k0ga@shike2.com>
Date:   Tue,  7 Mar 2017 20:56:46 +0100

[libc] Fix exit() and atexit()

Functions registered with atexit() must be called
in reverse order. This implementation also protects
against calling exit() from an atexit() handler.

Diffstat:
M
libc/include/errno.h
 | 
1
+
M
libc/src/atexit.c
 | 
18
+++++++++---------
M
libc/src/exit.c
 | 
14
++++----------

3 files changed, 14 insertions(+), 19 deletions(-)
diff --git a/libc/include/errno.h b/libc/include/errno.h
@@ -5,6 +5,7 @@
 #define EDOM   1
 #define EILSEQ 2
 #define ERANGE 3
+#define ENOMEN 4
 
 extern int errno;
 
diff --git a/libc/src/atexit.c b/libc/src/atexit.c
@@ -1,19 +1,19 @@
 /* See LICENSE file for copyright and license details. */
 
 #include <stdlib.h>
+#include <errno.h>
 #undef atexit
 
-extern void (*_atexitf[_ATEXIT_MAX])(void);
+extern void (*_exitf[_ATEXIT_MAX])(void);
+extern unsigned _exitn;
 
 int
 atexit(void (*fun)(void))
 {
-	void (**bp)(void);
-
-	for (bp = _atexitf; bp < &_atexitf[_ATEXIT_MAX] && *bp; ++bp)
-		/* nothing */;
-	if (bp == &_atexitf[_ATEXIT_MAX])
-		return 0;
-	*bp = fun;
-	return 1;
+	if (_exitn == _ATEXIT_MAX) {
+		errno = ENOMEN;
+		return -1;
+	}
+	_exitf[_exitn++] = fun;
+	return 0;
 }
diff --git a/libc/src/exit.c b/libc/src/exit.c
@@ -3,19 +3,13 @@
 #include <stdlib.h>
 #undef exit
 
-void (*_atexitf[_ATEXIT_MAX])(void);
+void (*_exitf[_ATEXIT_MAX])(void);
+unsigned _exitn;
 
 void
 exit(int status)
 {
-	void (**bp)(void);
-	int i;
-
-	for (i = _ATEXIT_MAX-1; i >= 0; --i) {
-		if (bp = _atexit[i]) {
-			*_atexit[i] = NULL;
-			(*bp)();
-		}
-	}
+	while (_exitn > 0)
+		(*_exitf[--exitn])();
 	_Exit(status);
 }