This header conforms to the C11 standard
Reference: ISO/IEC 9899:201x 7.15 Alignment <stdalign.h>
According to ISO/IEC 9899:201x (draft) 7.15 Alignment <stdalign.h> defines
four macros:
- alignas which expands to _Alignas
- alignof which expands to _Alignof
- __alignas_is_defined and __alignof_is_defined which both expand to 1
The _Alignas declaration appears as one of the type specifiers to modify
the alignment requirement of the object being declared.
The _Alignof operator is used to query the alignment requirement of its
operand type.
ISO/IEC N3242=11-0012 (C++1x) and ISO/IEC N3797 (C++1y) both note a header
<cstdalign> which defines only __alignas_is_defined and shall not define
the alignas macro. It misses the alignof case as it's probably based on an
older C1x draft, which defined only alignas. Assume that this is a bug in
the standard and treat alignof the same way as alignas in C++11.
Allow to define alignas and alignof in C++ prior the C++11 standard. It
might be broken but a nonstandard C++ compiler might support C11-like
_Alignas and _Alignof. Note that it's fatal for g++(1) v.5.4.
This header conforms to the C11 standard
Reference: ISO/IEC 9899:201x 7.23 _Noreturn <stdnoreturn.h>
According to ISO/IEC 9899:201x (draft) <stdnoreturn.> defines the
noreturn macro which expands to _Noreturn.
The _Noreturn keyword appears in a function declaration and specifies
that the function does not return by reaching the end of the function
body.
Design choices:
- don't implicitly break C++ code including this header with #error
C++11 offers [[noreturn]] which conflicts with C11 _Noreturn
- don't check for __STDC_VERSION__, everybody is free to reuse it with
a nonstandard compiler not conforming to C11 but supporting _Noreturn
gcc(1) and clang(1) support _Noreturn in -std=c99 and older standards
this follows <stdbool.h> choice for not checking for C99
- follow <stdbool.h> and declare the __noreturn_is_defined guard
- use a standard header guard (_STDNORETURN_H_), similar to <stdbool.h>
Reviewed by <pgoyette> and <joerg>
Adding a whole extra header file just for this is not the optimal
solution... but stuffing it in with anything else exposes things that
otherwise wouldn't be.
Nothing in userland should use <sys/semaphore.h> directly, and if some
foolish third-party software should decide to do so anyway in spite of
the instructions to the contrary I will ruthlessly break it later when
the big kernel includes cleanup finally happens.
Reported by Kamil Rytarowski, and, as it turns out, also by Klaus
Heinz in 2008.
rather than doing the machine/ansi.h #ifdef dance, as it doesn't matter
much what symbols utmp.h exposes. This could be tightened later when we
manage to do enough include cleanup to make such dances less expensive
to maintain.
Also, dumprestore.h needs ufs/ufs/dinode.h; in talkd.h use unsigned
char instead of u_char; and in timed.h include limits.h and use
_POSIX_HOST_NAME_MAX instead of MAXHOSTNAMELEN as the latter would
require sys/param.h.
NetBSD's PTHREAD_KEYS_MAX is set to 256, which is low compared to
other systems like Linux (1024) or MacOS X (512). As a result some
setups tested on Linux will exhibit problems on NetBSD because of
pthread_keys usage beyond the limit. This happens for instance on
Apache with various module loaded, and in this case no particular
developper can be blamed for going beyond the limit, since several
modules from different sources contribute to the problem.
This patch makes the limit conigurable through the PTHREAD_KEYS_MAX
environement variable. If undefined, the default remains unchanged
(256). In any case, the value cannot be lowered below POSIX-mandated
_POSIX_THREAD_KEYS_MAX (128).
While there:
- use EXIT_FAILURE instead of 1 when calling err(3) in libpthread.
- Reset _POSIX_THREAD_KEYS_MAX to POSIX mandated 128, instead of 256.
checks. Compared to OpenBSD's reallocarray, makes it easier to avoid memory
leaks on allocation failures and it doesn't depend on malloc(0) != NULL
for correct error checking. Compared to plain realloc, it also avoids
the problem of intermediate integer overflows. The trade-off is the use
of void * to side step C type system with regard to generic pointer to
pointer.
kamil