include/linux/compiler.h | 8 ++++++++ include/linux/const.h | 8 -------- tools/include/linux/const.h | 8 -------- 3 files changed, 8 insertions(+), 16 deletions(-)
Prior to f747e6667ebb2 __is_constexpr() was in its only user minmax.h.
That commit moved it to const.h - but that file just defined ULL(x) and
UL(x) so that constants can be defined for .S and .c files.
So apart from the word 'const' it wasn't really a good location.
Instead move the definition to compiler.h just before the similar
is_signed_type() and is_unsigned_type().
(Which were moved there by dcf8e5633e2e6)
This may not be a good long-term home, but the three definitions
belong together.
Signed-off-by: David Laight <david.laight@aculab.com>
---
This makes it possible to use __is_constexpr() inside is_signed_type()
so that the result is constant integer expression for pointer types.
In particular (void *)1 isn't constant enough.
include/linux/compiler.h | 8 ++++++++
include/linux/const.h | 8 --------
tools/include/linux/const.h | 8 --------
3 files changed, 8 insertions(+), 16 deletions(-)
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index d7779a18b24f..2efec9bfcc40 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -230,6 +230,14 @@ static inline void *offset_to_ptr(const int *off)
/* &a[0] degrades to a pointer: a different type from an array */
#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
+/*
+ * This returns a constant expression while determining if an argument is
+ * a constant expression, most importantly without evaluating the argument.
+ * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
+ */
+#define __is_constexpr(x) \
+ (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
+
/*
* Whether 'type' is a signed type or an unsigned type. Supports scalar types,
* bool and also pointer types.
diff --git a/include/linux/const.h b/include/linux/const.h
index 435ddd72d2c4..81b8aae5a855 100644
--- a/include/linux/const.h
+++ b/include/linux/const.h
@@ -3,12 +3,4 @@
#include <vdso/const.h>
-/*
- * This returns a constant expression while determining if an argument is
- * a constant expression, most importantly without evaluating the argument.
- * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
- */
-#define __is_constexpr(x) \
- (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
-
#endif /* _LINUX_CONST_H */
diff --git a/tools/include/linux/const.h b/tools/include/linux/const.h
index 435ddd72d2c4..81b8aae5a855 100644
--- a/tools/include/linux/const.h
+++ b/tools/include/linux/const.h
@@ -3,12 +3,4 @@
#include <vdso/const.h>
-/*
- * This returns a constant expression while determining if an argument is
- * a constant expression, most importantly without evaluating the argument.
- * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
- */
-#define __is_constexpr(x) \
- (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
-
#endif /* _LINUX_CONST_H */
--
2.17.1
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)On Mon, Oct 02, 2023 at 02:34:05PM +0000, David Laight wrote: > Prior to f747e6667ebb2 __is_constexpr() was in its only user minmax.h. > That commit moved it to const.h - but that file just defined ULL(x) and > UL(x) so that constants can be defined for .S and .c files. > So apart from the word 'const' it wasn't really a good location. > Instead move the definition to compiler.h just before the similar > is_signed_type() and is_unsigned_type(). > (Which were moved there by dcf8e5633e2e6) > This may not be a good long-term home, but the three definitions > belong together. > > Signed-off-by: David Laight <david.laight@aculab.com> > --- > This makes it possible to use __is_constexpr() inside is_signed_type() > so that the result is constant integer expression for pointer types. > In particular (void *)1 isn't constant enough. > > include/linux/compiler.h | 8 ++++++++ > include/linux/const.h | 8 -------- > tools/include/linux/const.h | 8 -------- > 3 files changed, 8 insertions(+), 16 deletions(-) > > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index d7779a18b24f..2efec9bfcc40 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -230,6 +230,14 @@ static inline void *offset_to_ptr(const int *off) > /* &a[0] degrades to a pointer: a different type from an array */ > #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0])) > > +/* > + * This returns a constant expression while determining if an argument is > + * a constant expression, most importantly without evaluating the argument. > + * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de> > + */ > +#define __is_constexpr(x) \ > + (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) > + > /* > * Whether 'type' is a signed type or an unsigned type. Supports scalar types, > * bool and also pointer types. > diff --git a/include/linux/const.h b/include/linux/const.h > index 435ddd72d2c4..81b8aae5a855 100644 > --- a/include/linux/const.h > +++ b/include/linux/const.h > @@ -3,12 +3,4 @@ > > #include <vdso/const.h> > > -/* > - * This returns a constant expression while determining if an argument is > - * a constant expression, most importantly without evaluating the argument. > - * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de> > - */ > -#define __is_constexpr(x) \ > - (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) > - > #endif /* _LINUX_CONST_H */ > diff --git a/tools/include/linux/const.h b/tools/include/linux/const.h > index 435ddd72d2c4..81b8aae5a855 100644 > --- a/tools/include/linux/const.h > +++ b/tools/include/linux/const.h > @@ -3,12 +3,4 @@ > > #include <vdso/const.h> > > -/* > - * This returns a constant expression while determining if an argument is > - * a constant expression, most importantly without evaluating the argument. > - * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de> > - */ > -#define __is_constexpr(x) \ > - (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) Doesn't tools/ still need its own copy somewhere? -Kees > - > #endif /* _LINUX_CONST_H */ > -- > 2.17.1 > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) > -- Kees Cook
From: Kees Cook > Sent: 02 October 2023 17:48 > > On Mon, Oct 02, 2023 at 02:34:05PM +0000, David Laight wrote: > > Prior to f747e6667ebb2 __is_constexpr() was in its only user minmax.h. > > That commit moved it to const.h - but that file just defined ULL(x) and > > UL(x) so that constants can be defined for .S and .c files. > > So apart from the word 'const' it wasn't really a good location. > > Instead move the definition to compiler.h just before the similar > > is_signed_type() and is_unsigned_type(). > > (Which were moved there by dcf8e5633e2e6) > > This may not be a good long-term home, but the three definitions > > belong together. > > ... > > diff --git a/tools/include/linux/const.h b/tools/include/linux/const.h > > index 435ddd72d2c4..81b8aae5a855 100644 > > --- a/tools/include/linux/const.h > > +++ b/tools/include/linux/const.h > > @@ -3,12 +3,4 @@ > > > > #include <vdso/const.h> > > > > -/* > > - * This returns a constant expression while determining if an argument is > > - * a constant expression, most importantly without evaluating the argument. > > - * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de> > > - */ > > -#define __is_constexpr(x) \ > > - (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) > > Doesn't tools/ still need its own copy somewhere? Nothing failed to build with it removed... I think I decided that tools actually used compiler.h. There weren't extra definitions of is_signed_type(). David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
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