[next,1/1] Use _Generic() to implement __is_constexpr()
Commit Message
This is somewhat more obvious than relying on sizeof(void) being 1.
It is also portable to any c11 compiler.
Change the constants to 0 - they have no bearing on the result and
just confuse the reader.
It relies on the type of (expr ? NULL : (type *)any) being 'type *'
but that of (expr ? (void *)x : (type *)any) being 'void *'.
Signed-off-by: David Laight <david.laight@aculab.com>
---
I'm not 100% sure all of 'tools' sets -std=gnu99 or -std=c11 to get
_Generic() supported.
This version will also be usable in 'nolibc' where sizeof(void) is
an error.
include/linux/compiler.h | 2 +-
tools/include/linux/compiler.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
@@ -233,7 +233,7 @@ static inline void *offset_to_ptr(const int *off)
* Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
*/
#define __is_constexpr(x) \
- (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
+ _Generic(0 ? (void *)((long)(x) * 0) : (char *)0, char *: 1, void *: 0)
/*
* Whether 'type' is a signed type or an unsigned type. Supports scalar types,
@@ -69,7 +69,7 @@
* Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
*/
#define __is_constexpr(x) \
- (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
+ _Generic(0 ? (void *)((long)(x) * 0) : (char *)0, char *: 1, void *: 0)
#ifdef __ANDROID__
/*