* Ping: Re: [PATCH v4] <sys/param.h>: Add nitems()
2020-09-28 19:12 [PATCH v4] <sys/param.h>: Add nitems() Alejandro Colomar
@ 2020-10-11 16:43 ` Alejandro Colomar
2020-10-27 11:38 ` Ping(2): " Alejandro Colomar
2020-11-17 22:23 ` Ping(3): " Alejandro Colomar
2 siblings, 0 replies; 8+ messages in thread
From: Alejandro Colomar @ 2020-10-11 16:43 UTC (permalink / raw)
To: libc-alpha
Cc: libc-coord, libstdc++,
gcc, linux-kernel, linux-man, jwakely, fweimer,
ville.voutilainen, enh, rusty
Ping.
On 2020-09-28 21:12, Alejandro Colomar wrote:
> 'nitems()' calculates the length of an array in number of items.
> It is safe: if a pointer is passed to the macro (or function, in C++),
> the compilation is broken due to:
> - In >= C11: _Static_assert()
> - In C89, C99: Negative anonymous bitfield
> - In C++: The template requires an array
>
> Some BSDs already provide a macro nitems() in <sys/param.h>,
> although it usually doesn't provide safety against pointers.
>
> This patch uses the same name for compatibility reasons,
> and to be the least disruptive with existing code.
>
> This patch also adds some other macros, which are required by 'nitems()':
>
> __is_same_type(a, b):
> Returns non-zero if the two input arguments are of the same type.
>
> __is_array(arr):
> Returns non-zero if the input argument is of an array type.
>
> __must_be(expr, msg):
> Allows using _Static_assert() everywhere an expression can be used.
> It evaluates '(int)0' or breaks the compilation.
>
> __must_be_array(arr):
> It evaluates to '(int)0' if the argument is of an array type.
> Else, it breaks compilation.
>
> __nitems(arr):
> It implements the basic sizeof division needed to calculate the array length.
>
>
> P.S.: I'd like to put this patch in the public domain.
>
> Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
> ---
>
> A few changes since v3:
>
> - Macros don't need reserved names in their parameters,
> so I simplified those names.
>
> - I fixed some wrong indentation levels.
>
> - Renamed __array_len() to __nitems() for consistency.
>
>
> misc/sys/param.h | 47 +++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 47 insertions(+)
>
> diff --git a/misc/sys/param.h b/misc/sys/param.h
> index d7c319b157..08d4093961 100644
> --- a/misc/sys/param.h
> +++ b/misc/sys/param.h
> @@ -102,5 +102,52 @@
> #define MIN(a,b) (((a)<(b))?(a):(b))
> #define MAX(a,b) (((a)>(b))?(a):(b))
>
> +/* Macros related to the types of variables */
> +#define __is_same_type(a, b) \
> + __builtin_types_compatible_p(__typeof__(a), __typeof__(b))
> +#define __is_array(arr) (!__is_same_type((arr), &(arr)[0]))
> +
> +/* Macros for embedding _Static_assert() in expressions */
> +#if __STDC_VERSION__ >= 201112L
> +# define __must_be(expr, msg) ( \
> + 0 * (int)sizeof( \
> + struct { \
> + _Static_assert((expr), msg); \
> + char _ISO_C_forbids_a_struct_with_no_members; \
> + } \
> + ) \
> +)
> +#else
> +# define __must_be(expr, msg) ( \
> + 0 * (int)sizeof( \
> + struct { \
> + int : (-!(expr)); \
> + char _ISO_C_forbids_a_struct_with_no_members; \
> + } \
> + ) \
> +)
> +#endif
> +#define __must_be_array(arr) __must_be(__is_array(arr), "Must be an array!")
> +
> +/* Macros for array sizes */
> +#if defined(__cplusplus)
> +# if __cplusplus >= 201103L
> +template<typename _Tp, std::size_t _Len>
> + constexpr inline std::size_t
> + nitems(const _Tp(&)[_Len]) __THROW
> + {
> + return _Len;
> + }
> +# else /* __cplusplus < 201103L */
> +template<typename _Tp, std::size_t _Len>
> + char
> + (&__nitems_chararr(const _Tp(&)[_Len]))[_Len];
> +# define nitems(arr) (sizeof(__nitems_chararr(arr)))
> +# endif /* __cplusplus < 201103L */
> +#else /* !defined(__cplusplus) */
> +# define __nitems(arr) (sizeof((arr)) / sizeof((arr)[0]))
> +# define nitems(arr) (__nitems(arr) + __must_be_array(arr))
> +#endif /* !defined(__cplusplus) */
> +
>
> #endif /* sys/param.h */
>
^ permalink raw reply [flat|nested] 8+ messages in thread* Ping(2): [PATCH v4] <sys/param.h>: Add nitems()
2020-09-28 19:12 [PATCH v4] <sys/param.h>: Add nitems() Alejandro Colomar
2020-10-11 16:43 ` Ping: " Alejandro Colomar
@ 2020-10-27 11:38 ` Alejandro Colomar
2020-11-17 22:23 ` Ping(3): " Alejandro Colomar
2 siblings, 0 replies; 8+ messages in thread
From: Alejandro Colomar @ 2020-10-27 11:38 UTC (permalink / raw)
To: libc-alpha, libc-coord
Cc: libstdc++,
gcc, linux-kernel, linux-man, jwakely, fweimer,
ville.voutilainen, enh, rusty
Ping
On 2020-09-28 21:12, Alejandro Colomar wrote:
> 'nitems()' calculates the length of an array in number of items.
> It is safe: if a pointer is passed to the macro (or function, in C++),
> the compilation is broken due to:
> - In >= C11: _Static_assert()
> - In C89, C99: Negative anonymous bitfield
> - In C++: The template requires an array
>
> Some BSDs already provide a macro nitems() in <sys/param.h>,
> although it usually doesn't provide safety against pointers.
>
> This patch uses the same name for compatibility reasons,
> and to be the least disruptive with existing code.
>
> This patch also adds some other macros, which are required by 'nitems()':
>
> __is_same_type(a, b):
> Returns non-zero if the two input arguments are of the same type.
>
> __is_array(arr):
> Returns non-zero if the input argument is of an array type.
>
> __must_be(expr, msg):
> Allows using _Static_assert() everywhere an expression can be used.
> It evaluates '(int)0' or breaks the compilation.
>
> __must_be_array(arr):
> It evaluates to '(int)0' if the argument is of an array type.
> Else, it breaks compilation.
>
> __nitems(arr):
> It implements the basic sizeof division needed to calculate the array length.
>
>
> P.S.: I'd like to put this patch in the public domain.
>
> Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
> ---
>
> A few changes since v3:
>
> - Macros don't need reserved names in their parameters,
> so I simplified those names.
>
> - I fixed some wrong indentation levels.
>
> - Renamed __array_len() to __nitems() for consistency.
>
>
> misc/sys/param.h | 47 +++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 47 insertions(+)
>
> diff --git a/misc/sys/param.h b/misc/sys/param.h
> index d7c319b157..08d4093961 100644
> --- a/misc/sys/param.h
> +++ b/misc/sys/param.h
> @@ -102,5 +102,52 @@
> #define MIN(a,b) (((a)<(b))?(a):(b))
> #define MAX(a,b) (((a)>(b))?(a):(b))
>
> +/* Macros related to the types of variables */
> +#define __is_same_type(a, b) \
> + __builtin_types_compatible_p(__typeof__(a), __typeof__(b))
> +#define __is_array(arr) (!__is_same_type((arr), &(arr)[0]))
> +
> +/* Macros for embedding _Static_assert() in expressions */
> +#if __STDC_VERSION__ >= 201112L
> +# define __must_be(expr, msg) ( \
> + 0 * (int)sizeof( \
> + struct { \
> + _Static_assert((expr), msg); \
> + char _ISO_C_forbids_a_struct_with_no_members; \
> + } \
> + ) \
> +)
> +#else
> +# define __must_be(expr, msg) ( \
> + 0 * (int)sizeof( \
> + struct { \
> + int : (-!(expr)); \
> + char _ISO_C_forbids_a_struct_with_no_members; \
> + } \
> + ) \
> +)
> +#endif
> +#define __must_be_array(arr) __must_be(__is_array(arr), "Must be an array!")
> +
> +/* Macros for array sizes */
> +#if defined(__cplusplus)
> +# if __cplusplus >= 201103L
> +template<typename _Tp, std::size_t _Len>
> + constexpr inline std::size_t
> + nitems(const _Tp(&)[_Len]) __THROW
> + {
> + return _Len;
> + }
> +# else /* __cplusplus < 201103L */
> +template<typename _Tp, std::size_t _Len>
> + char
> + (&__nitems_chararr(const _Tp(&)[_Len]))[_Len];
> +# define nitems(arr) (sizeof(__nitems_chararr(arr)))
> +# endif /* __cplusplus < 201103L */
> +#else /* !defined(__cplusplus) */
> +# define __nitems(arr) (sizeof((arr)) / sizeof((arr)[0]))
> +# define nitems(arr) (__nitems(arr) + __must_be_array(arr))
> +#endif /* !defined(__cplusplus) */
> +
>
> #endif /* sys/param.h */
>
^ permalink raw reply [flat|nested] 8+ messages in thread* Ping(3): [PATCH v4] <sys/param.h>: Add nitems()
2020-09-28 19:12 [PATCH v4] <sys/param.h>: Add nitems() Alejandro Colomar
2020-10-11 16:43 ` Ping: " Alejandro Colomar
2020-10-27 11:38 ` Ping(2): " Alejandro Colomar
@ 2020-11-17 22:23 ` Alejandro Colomar
2020-11-17 22:44 ` Joseph Myers
2 siblings, 1 reply; 8+ messages in thread
From: Alejandro Colomar @ 2020-11-17 22:23 UTC (permalink / raw)
To: libc-alpha, libc-coord
Cc: libstdc++,
gcc, linux-kernel, linux-man, jwakely, fweimer,
ville.voutilainen, enh, rusty
Hi,
Do you think the patch is ready,
or is there anything else I should do before merging it?
Thanks,
Alex
On 9/28/20 9:12 PM, Alejandro Colomar wrote:
> 'nitems()' calculates the length of an array in number of items.
> It is safe: if a pointer is passed to the macro (or function, in C++),
> the compilation is broken due to:
> - In >= C11: _Static_assert()
> - In C89, C99: Negative anonymous bitfield
> - In C++: The template requires an array
>
> Some BSDs already provide a macro nitems() in <sys/param.h>,
> although it usually doesn't provide safety against pointers.
>
> This patch uses the same name for compatibility reasons,
> and to be the least disruptive with existing code.
>
> This patch also adds some other macros, which are required by 'nitems()':
>
> __is_same_type(a, b):
> Returns non-zero if the two input arguments are of the same type.
>
> __is_array(arr):
> Returns non-zero if the input argument is of an array type.
>
> __must_be(expr, msg):
> Allows using _Static_assert() everywhere an expression can be used.
> It evaluates '(int)0' or breaks the compilation.
>
> __must_be_array(arr):
> It evaluates to '(int)0' if the argument is of an array type.
> Else, it breaks compilation.
>
> __nitems(arr):
> It implements the basic sizeof division needed to calculate the array length.
>
>
> P.S.: I'd like to put this patch in the public domain.
>
> Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
> ---
>
> A few changes since v3:
>
> - Macros don't need reserved names in their parameters,
> so I simplified those names.
>
> - I fixed some wrong indentation levels.
>
> - Renamed __array_len() to __nitems() for consistency.
>
>
> misc/sys/param.h | 47 +++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 47 insertions(+)
>
> diff --git a/misc/sys/param.h b/misc/sys/param.h
> index d7c319b157..08d4093961 100644
> --- a/misc/sys/param.h
> +++ b/misc/sys/param.h
> @@ -102,5 +102,52 @@
> #define MIN(a,b) (((a)<(b))?(a):(b))
> #define MAX(a,b) (((a)>(b))?(a):(b))
>
> +/* Macros related to the types of variables */
> +#define __is_same_type(a, b) \
> + __builtin_types_compatible_p(__typeof__(a), __typeof__(b))
> +#define __is_array(arr) (!__is_same_type((arr), &(arr)[0]))
> +
> +/* Macros for embedding _Static_assert() in expressions */
> +#if __STDC_VERSION__ >= 201112L
> +# define __must_be(expr, msg) ( \
> + 0 * (int)sizeof( \
> + struct { \
> + _Static_assert((expr), msg); \
> + char _ISO_C_forbids_a_struct_with_no_members; \
> + } \
> + ) \
> +)
> +#else
> +# define __must_be(expr, msg) ( \
> + 0 * (int)sizeof( \
> + struct { \
> + int : (-!(expr)); \
> + char _ISO_C_forbids_a_struct_with_no_members; \
> + } \
> + ) \
> +)
> +#endif
> +#define __must_be_array(arr) __must_be(__is_array(arr), "Must be an array!")
> +
> +/* Macros for array sizes */
> +#if defined(__cplusplus)
> +# if __cplusplus >= 201103L
> +template<typename _Tp, std::size_t _Len>
> + constexpr inline std::size_t
> + nitems(const _Tp(&)[_Len]) __THROW
> + {
> + return _Len;
> + }
> +# else /* __cplusplus < 201103L */
> +template<typename _Tp, std::size_t _Len>
> + char
> + (&__nitems_chararr(const _Tp(&)[_Len]))[_Len];
> +# define nitems(arr) (sizeof(__nitems_chararr(arr)))
> +# endif /* __cplusplus < 201103L */
> +#else /* !defined(__cplusplus) */
> +# define __nitems(arr) (sizeof((arr)) / sizeof((arr)[0]))
> +# define nitems(arr) (__nitems(arr) + __must_be_array(arr))
> +#endif /* !defined(__cplusplus) */
> +
>
> #endif /* sys/param.h */
>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: Ping(3): [PATCH v4] <sys/param.h>: Add nitems()
2020-11-17 22:23 ` Ping(3): " Alejandro Colomar
@ 2020-11-17 22:44 ` Joseph Myers
2020-11-17 22:59 ` Alejandro Colomar
0 siblings, 1 reply; 8+ messages in thread
From: Joseph Myers @ 2020-11-17 22:44 UTC (permalink / raw)
To: Alejandro Colomar
Cc: libc-alpha, libc-coord, fweimer, gcc, ville.voutilainen,
linux-man, rusty, linux-kernel, libstdc++,
jwakely, enh
I've asked the WG14 reflector why N2529 (and N2530, though that one's not
relevant to this feature) doesn't seem to have made it onto a meeting
agenda yet, when there have been two WG14 meetings since that proposal was
made and a third one coming up.
--
Joseph S. Myers
joseph@codesourcery.com
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Ping(3): [PATCH v4] <sys/param.h>: Add nitems()
2020-11-17 22:44 ` Joseph Myers
@ 2020-11-17 22:59 ` Alejandro Colomar
2020-11-17 23:11 ` Joseph Myers
0 siblings, 1 reply; 8+ messages in thread
From: Alejandro Colomar @ 2020-11-17 22:59 UTC (permalink / raw)
To: Joseph Myers
Cc: libc-alpha, libc-coord, fweimer, gcc, ville.voutilainen,
linux-man, rusty, linux-kernel, libstdc++,
jwakely, enh
Hi Joseph,
On 11/17/20 11:44 PM, Joseph Myers wrote:
> I've asked the WG14 reflector why N2529 (and N2530, though that one's not
> relevant to this feature) doesn't seem to have made it onto a meeting
> agenda yet, when there have been two WG14 meetings since that proposal
was
> made and a third one coming up.
>
Nice!
Please update me on any feedback you receive.
So glibc will basically hold this patch
at least until the WG answers to that, right?
Thanks,
Alex
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Ping(3): [PATCH v4] <sys/param.h>: Add nitems()
2020-11-17 22:59 ` Alejandro Colomar
@ 2020-11-17 23:11 ` Joseph Myers
2020-11-18 11:26 ` Alejandro Colomar
0 siblings, 1 reply; 8+ messages in thread
From: Joseph Myers @ 2020-11-17 23:11 UTC (permalink / raw)
To: Alejandro Colomar
Cc: fweimer, gcc, ville.voutilainen, linux-man, rusty, linux-kernel,
libstdc++,
libc-coord, libc-alpha, jwakely, enh
On Tue, 17 Nov 2020, Alejandro Colomar via Libc-alpha wrote:
> Nice!
> Please update me on any feedback you receive.
Apparently the author is planning new versions of those papers so WG14
discussion is waiting for those.
> So glibc will basically hold this patch
> at least until the WG answers to that, right?
I think that whether C2x gets an array-size feature of some kind is
relevant to whether such a feature goes in glibc and what it looks like in
glibc, but the fact that it will be considered in WG14 doesn't rule out
glibc considering such a feature without waiting for WG14.
--
Joseph S. Myers
joseph@codesourcery.com
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Ping(3): [PATCH v4] <sys/param.h>: Add nitems()
2020-11-17 23:11 ` Joseph Myers
@ 2020-11-18 11:26 ` Alejandro Colomar
0 siblings, 0 replies; 8+ messages in thread
From: Alejandro Colomar @ 2020-11-18 11:26 UTC (permalink / raw)
To: Joseph Myers
Cc: fweimer, gcc, ville.voutilainen, linux-man, rusty, linux-kernel,
libstdc++,
libc-coord, libc-alpha, jwakely, enh
On 11/18/20 12:11 AM, Joseph Myers wrote:
> On Tue, 17 Nov 2020, Alejandro Colomar via Libc-alpha wrote:
>
>> Nice!
>> Please update me on any feedback you receive.
>
> Apparently the author is planning new versions of those papers so WG14
> discussion is waiting for those.
>
>> So glibc will basically hold this patch
>> at least until the WG answers to that, right?
>
> I think that whether C2x gets an array-size feature of some kind is
> relevant to whether such a feature goes in glibc and what it looks like in
> glibc, but the fact that it will be considered in WG14 doesn't rule out
> glibc considering such a feature without waiting for WG14.
>
Hi Joseph,
Yes, that's what I would expect, but it's been a long time since I sent
the patch, so that's why I asked.
Maybe glibc is busy now with other more urgent things, I don't know.
Thanks,
Alex
^ permalink raw reply [flat|nested] 8+ messages in thread