In article <[EMAIL PROTECTED]>,
Doug Rabson <[EMAIL PROTECTED]> wrote:
> On Tue, 29 Oct 2002, John Polstra wrote:
> > I think it would work if the symbol were defined strongly in libc_r.
>
> I think so too. I was trying to work out why this wasn't how things were
> done already. FWIW, linux's libpthread appears to be defining the
> pthread_* symbols strongly.
I think the weak symbols have something to do with support for thread
cancellation. I didn't pay much attention at the time, so I don't
know the details. Here's the relevant commit message, I think (this
one taken from lib/libc_r/uthread/uthread_pause.c):
date: 2001/01/24 13:03:34; author: deischen; state: Exp; lines: +4 -4
Add weak definitions for wrapped system calls. In general:
_foo - wrapped system call
foo - weak definition to _foo
and for cancellation points:
_foo - wrapped system call
__foo - enter cancellation point, call _foo(), leave
cancellation point
foo - weak definition to __foo
Change use of global _thread_run to call a function to get the
currently running thread.
Make all pthread_foo functions weak definitions to _pthread_foo,
where _pthread_foo is the implementation. This allows an application
to provide its own pthread functions.
Provide slightly different versions of pthread_mutex_lock and
pthread_mutex_init so that we can tell the difference between
a libc mutex and an application mutex. Threads holding mutexes
internal to libc should never be allowed to exit, call signal
handlers, or cancel.
Approved by: -arch
John
--
John Polstra
John D. Polstra & Co., Inc. Seattle, Washington USA
"Disappointment is a good sign of basic intelligence." -- Chögyam Trungpa
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