bde at zeta.org.au
Sat Aug 20 05:48:35 GMT 2005
On Fri, 19 Aug 2005, Stefan Farfeleder wrote:
> On Sat, Aug 20, 2005 at 12:04:56AM +1000, Bruce Evans wrote:
>> On Fri, 19 Aug 2005, Stefan Farfeleder wrote:
>>> I think some of the headers included by <pthread.h> violate the POSIX
>>> specification (I'm looking at SUSv3/POSIX 1003.1 2004) by making more
>>> symbols visible than allowed.
>>> <sys/cdefs.h> Ok
>>> <sys/types.h> Ok
>>> <sys/_pthreadtypes.h> Ok
>>> <sys/time.h> No? (POSIX allows <time.h> which is a subset)
> Actually POSIX kind of requires the inclusion of <time.h> (and
> <sched.h>). At least all symbols must be visible.
Urk. This seems to be the place in POSIX where namespace pollution is
explictly required. According to an old draft:
10351 Inclusion of the <pthread.h> header shall make symbols defined in the headers <sched.h> and
10352 <time.h> visible.
Everywhere else, POSIX permits both broken and non-broken implementations
by saying "may make visible".
The history of this is interesting:
10408 IEEE PASC Interpretation 1003.1 #86 is applied, allowing the symbols from <sched.h> and
10409 <time.h> to be made visible when <pthread.h> is included. Previously this was an XSI
The weasels who wrote "may" were apparently not present when this was
10411 IEEE PASC Interpretation 1003.1c #42 is applied, removing the requirement for prototypes for
10412 the pthread_kill ( ) and pthread_sigmask( ) functions. These are required to be in the <signal.h>
10413 header. They are allowed here through the name space rules.
sigset_t apparently isn't required here either.
>> <sys/cdefs.h> needed, but can be obtained as a side effect
>> of including almost any other header in the list.
>> <sys/types.h> only used to declare size_t. We handle this better
>> in many other headers. The old draft of POSIX that
>> I'm looking at doesn't say that <pthread.h> declares
>> size_t, so it might be conformant to use __size_t
>> in the prototypes.
> Removed, size_t is obtained via <time.h>.
>> <sys/time.h> only used to declare sigset_t and struct timespec.
>> We have a whole header, <sys/_sigset.h>, to help
>> declare sigset_t better (it only declares
> I've include <machine/_types.h> (for __uint32_t) and <sys/_sigset.h>
> instead. timespec is declared through <time.h>.
>> <sys/signal.h> Just namespace pollution.
> We need MINSIGSTKSZ from <machine/signal.h> though. The patch includes
> that header instead and protects its usage with __XSI_VISIBLE. I'm not
> happy with this, maybe MINSIGSTKSZ should be moved somewhere else?
MINSIGSTKSZ is used to define PTHREAD_STACK_MIN. I didn't notice this
partly because the old version that I looked at correctly defiens
PTHREAD_STACK_MIN as a constant. Everything is wrong here:
- POSIX requires PTHREAD_STACK_MIN to be defined (if at all) in
<limits.h> but not in <pthread.h>.
- PTHREAD_STACK_MIN must be defined as a number (if at all even if
XSI is no visible.
>> <limits.h> Just namespace pollution.
> <machine/_limits.h> is included instead and __ULONG_MAX is used.
__ULONG_MAX is used to define PTHREAD_THREADS_MAX. POSIX actually requires
the latter to be defined (if at all) in <limits.h> only too. I doubt
that the limit is actually 2^64-1. Maybe it should be a runtime limit
_SC_THREAD* are missing, so apparently no one ever asks for the runtime
>> <sched.h> only used to declare struct sched_param and to
>> satisfy a POSIX mistake. A forward declaration
>> would suffice.
> Left because POSIX says so.
Not too bad.
> The patch for <pthread.h> is at
> http://people.freebsd.org/~stefanf/pthread.h.diff .
> There are a few files that need <sys/types>, <limits.h>, etc symbols and
> get them by <pthread.h> inclusion, the patch at
> http://people.freebsd.org/~stefanf/pthread.h-2.diff fixes that. It
> should probably be committed anyway.
An alarming number. We shouldn't need so many new includes of
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