Module Name: src
Committed By: kamil
Date: Sun Sep 22 23:13:10 UTC 2019
Modified Files:
src/sys/sys: cdefs.h
Log Message:
Make __CTASSERT static assert again
Today GCC/Clang allow to specify typedef char[] with the dynamic VLA
property (as introduced in C99). This means that __CTASSERT(), when
misused with run-time semantics, was a dummy check generating either
1 or -1 size of typedef char[].
It was caught in runtime by kUBSan as -1 is size of VLA with unspecified
semantics in runtime (Undefined Behavior).
Use bit-field to enforce compile-time constant.
This approach has been inspired by the Perl variation of static_assert().
To generate a diff of this commit:
cvs rdiff -u -r1.144 -r1.145 src/sys/sys/cdefs.h
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/sys/cdefs.h
diff -u src/sys/sys/cdefs.h:1.144 src/sys/sys/cdefs.h:1.145
--- src/sys/sys/cdefs.h:1.144 Wed Sep 18 15:06:03 2019
+++ src/sys/sys/cdefs.h Sun Sep 22 23:13:10 2019
@@ -1,4 +1,4 @@
-/* $NetBSD: cdefs.h,v 1.144 2019/09/18 15:06:03 kamil Exp $ */
+/* $NetBSD: cdefs.h,v 1.145 2019/09/22 23:13:10 kamil Exp $ */
/* * Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
@@ -172,8 +172,11 @@
#define __CTASSERT99(x, a, b) __CTASSERT0(x, __CONCAT(__ctassert,a), \
__CONCAT(_,b))
#endif
-#define __CTASSERT0(x, y, z) __CTASSERT1(x, y, z)
-#define __CTASSERT1(x, y, z) typedef char y ## z[/*CONSTCOND*/(x) ? 1 : -1] __unused
+#define __CTASSERT0(x, y, z) __CTASSERT1(x, y, z)
+#define __CTASSERT1(x, y, z) \
+ typedef struct { \
+ unsigned int y ## z : /*CONSTCOND*/(x) ? 1 : -1; \
+ } y ## z ## _struct __unused
/*
* The following macro is used to remove const cast-away warnings
