[3/8] sys/types.h: Don’t define u_intN_t or register_t unless __USE_MISC.
Commit Message
sys/types.h unconditionally defines u_int8_t, u_int16_t, u_int32_t,
u_int64_t, and register_t. These are not part of any standard. The
u_intXX_t types are superseded by C99’s uintXX_t types (defined in
stdint.h). I’m not aware of a standardized exact equivalent of
register_t, but also I’ve never seen anyone use it for anything.
I could be persuaded to leave that one alone.
sys/types.h also unconditionally defines int8_t, int16_t, int32_t, and
int64_t, which are the same as the C99 exact-width signed types in
stdint.h. POSIX doesn’t require these to appear in sys/types.h, so in
principle they ought to be brought under __USE_MISC also. But, when I
tried that it broke about two dozen files just in our own source tree,
and POSIX doesn’t *forbid* sys/types.h to define these types, so I
think we should leave them alone.
* posix/sys/types.h (u_int8_t, u_int16_t, u_int32_t, u_int64_t)
(register_t): Move under #ifdef __USE_MISC.
Consolidate adjacent #ifdef __USE_MISC blocks.
* scripts/check_obsolete_constructs.py: Add register_t to the
set of obsolete typedefs that our headers should not use
(but sys/types.h may still define).
---
NEWS | 8 ++++++++
posix/sys/types.h | 16 ++++++++--------
scripts/check-obsolete-constructs.py | 1 +
3 files changed, 17 insertions(+), 8 deletions(-)
Comments
* Zack Weinberg:
> +* The typedefs u_int8_t, u_int16_t, u_int32_t, u_int64_t, and register_t
> + are no longer defined by <sys/types.h> in strict conformance modes.
> + These types were historically provided by <sys/types.h> on BSD systems,
> + but are not part of the POSIX specification for that header. Applications
> + requiring fixed-width unsigned integer types should use the similarly
> + named uint8_t, uint16_t, etc. from <stdint.h>. There is no standardized
> + replacement for register_t.
The challenge with register_t is that it's long long on x32 and MIPS64
with -mabi=n32.
And ideally, it would be the return type of the syscall function (which
is long int by incorrect tradition).
> diff --git a/posix/sys/types.h b/posix/sys/types.h
> index 1bbd896ad4..7327904346 100644
> --- a/posix/sys/types.h
> +++ b/posix/sys/types.h
> @@ -143,18 +143,20 @@ typedef __suseconds_t suseconds_t;
> #define __need_size_t
> #include <stddef.h>
>
> +/* POSIX does not require intN_t to be defined in this header, so
> + technically this ought to be under __USE_MISC, but it doesn't
> + forbid them to be defined here either, and much existing code
> + expects them to be defined here. */
> +#include <bits/stdint-intn.h>
> +
> #ifdef __USE_MISC
> /* Old compatibility names for C types. */
> typedef unsigned long int ulong;
> typedef unsigned short int ushort;
> typedef unsigned int uint;
> -#endif
>
> -/* These size-specific names are used by some of the inet code. */
> -
> -#include <bits/stdint-intn.h>
> -
> -/* These were defined by ISO C without the first `_'. */
> +/* These size-specific names are used by some of the inet code.
> + They were defined by ISO C without the first `_'. */
> typedef __uint8_t u_int8_t;
> typedef __uint16_t u_int16_t;
> typedef __uint32_t u_int32_t;
I think the comment refers to the same types as the comment above the
inclusion of <bits/stdint-intn.h>. Maybe that could be made more clear
to the casual reader?
Rest of the patch looks fine to me.
Thanks,
Florian
On Thu, May 9, 2019 at 4:34 AM Florian Weimer <fweimer@redhat.com> wrote:
> > +* The typedefs u_int8_t, u_int16_t, u_int32_t, u_int64_t, and register_t
> > + are no longer defined by <sys/types.h> in strict conformance modes.
> > + These types were historically provided by <sys/types.h> on BSD systems,
> > + but are not part of the POSIX specification for that header. Applications
> > + requiring fixed-width unsigned integer types should use the similarly
> > + named uint8_t, uint16_t, etc. from <stdint.h>. There is no standardized
> > + replacement for register_t.
>
> The challenge with register_t is that it's long long on x32 and MIPS64
> with -mabi=n32.
Yes, patch 2 of this series had to introduce a MIPS-specific
bits/typesizes.h because of this.
> And ideally, it would be the return type of the syscall function (which
> is long int by incorrect tradition).
I don't want to change that in this patch series.
[sys/types.h]
> > +/* POSIX does not require intN_t to be defined in this header, so
> > + technically this ought to be under __USE_MISC, but it doesn't
> > + forbid them to be defined here either, and much existing code
> > + expects them to be defined here. */
> > +#include <bits/stdint-intn.h>
...
> > -/* These were defined by ISO C without the first `_'. */
> > +/* These size-specific names are used by some of the inet code.
> > + They were defined by ISO C without the first `_'. */
> > typedef __uint8_t u_int8_t;
> > typedef __uint16_t u_int16_t;
> > typedef __uint32_t u_int32_t;
>
> I think the comment refers to the same types as the comment above the
> inclusion of <bits/stdint-intn.h>. Maybe that could be made more clear
> to the casual reader?
The important difference here is that intN_t are standard types (but
not standardized as provided by sys/types.h) so it's less troublesome
for us to provide them unconditionally, as existing code expects.
u_intN_t are not standard types so we really shouldn't provide them
unconditionally. How's this for a comment?
/* These alternative names for uintN_t were used by pre-C99 networking code.
Provided for backward compatibility only. */
> Rest of the patch looks fine to me.
Thanks. Nobody's looked at most of the rest of the patch series; do
you think you might have time to do it in the near future?
zw
@@ -26,6 +26,14 @@ Deprecated and removed features, and other changes affecting compatibility:
definitions in libc will be used automatically, which have been available
since glibc 2.17.
+* The typedefs u_int8_t, u_int16_t, u_int32_t, u_int64_t, and register_t
+ are no longer defined by <sys/types.h> in strict conformance modes.
+ These types were historically provided by <sys/types.h> on BSD systems,
+ but are not part of the POSIX specification for that header. Applications
+ requiring fixed-width unsigned integer types should use the similarly
+ named uint8_t, uint16_t, etc. from <stdint.h>. There is no standardized
+ replacement for register_t.
+
Changes to build and runtime requirements:
* GCC 6.2 or later is required to build the GNU C Library.
@@ -143,18 +143,20 @@ typedef __suseconds_t suseconds_t;
#define __need_size_t
#include <stddef.h>
+/* POSIX does not require intN_t to be defined in this header, so
+ technically this ought to be under __USE_MISC, but it doesn't
+ forbid them to be defined here either, and much existing code
+ expects them to be defined here. */
+#include <bits/stdint-intn.h>
+
#ifdef __USE_MISC
/* Old compatibility names for C types. */
typedef unsigned long int ulong;
typedef unsigned short int ushort;
typedef unsigned int uint;
-#endif
-/* These size-specific names are used by some of the inet code. */
-
-#include <bits/stdint-intn.h>
-
-/* These were defined by ISO C without the first `_'. */
+/* These size-specific names are used by some of the inet code.
+ They were defined by ISO C without the first `_'. */
typedef __uint8_t u_int8_t;
typedef __uint16_t u_int16_t;
typedef __uint32_t u_int32_t;
@@ -167,8 +169,6 @@ typedef __register_t register_t;
defined. */
#define __BIT_TYPES_DEFINED__ 1
-
-#ifdef __USE_MISC
/* In BSD <sys/types.h> is expected to define BYTE_ORDER. */
# include <endian.h>
@@ -254,6 +254,7 @@ class NoCheck(ConstructChecker):
OBSOLETE_TYPE_RE_ = re.compile(r"""\A
(__)?
( quad_t
+ | register_t
| u(?: short | int | long
| _(?: char | short | int(?:[0-9]+_t)? | long | quad_t )))
\Z""", re.VERBOSE)