path: root/include/string.h
diff options
authorRich Felker <>2013-11-24 21:42:55 -0500
committerRich Felker <>2013-11-24 21:42:55 -0500
commitc8a9c22173f485c8c053709e1dfa0a617cb6be1a (patch)
tree6e09d7e73bbff957b45370d412cc6299fe51eb37 /include/string.h
parent7e771e62e78944b9d1fe7e78ef71422b9d51f275 (diff)
restore type of NULL to void * except when used in C++ programs
unfortunately this eliminates the ability of the compiler to diagnose some dangerous/incorrect usage, but POSIX requires (as an extension to the C language, i.e. CX shaded) that NULL have type void *. plain C allows it to be defined as any null pointer constant. the definition 0L is preserved for C++ rather than reverting to plain 0 to avoid dangerous behavior in non-conforming programs which use NULL as a variadic sentinel. (it's impossible to use (void *)0 for C++ since C++ lacks the proper implicit pointer conversions, and other popular alternatives like the GCC __null extension seem non-conforming to the standard's requirements.)
Diffstat (limited to 'include/string.h')
1 files changed, 4 insertions, 0 deletions
diff --git a/include/string.h b/include/string.h
index d4412333..ff9badb9 100644
--- a/include/string.h
+++ b/include/string.h
@@ -7,7 +7,11 @@ extern "C" {
#include <features.h>
+#ifdef __cplusplus
#define NULL 0L
+#define NULL ((void*)0)
#define __NEED_size_t
#if defined(_POSIX_SOURCE) || defined(_POSIX_C_SOURCE) \