Re: [Boost-users] [thread] understanding multiple statically-linked boost::thread in same process

Subject: Re: [Boost-users] [thread] understanding multiple statically-linked boost::thread in same process
From: Gavin Lambert (gavinl_at_[hidden])
Date: 2017-01-30 18:19:53

On 28/01/2017 04:29, Simon Haegler wrote:
> i am debugging an application where several shared libraries contain
> statically-linked copies of boost::thread (and other boost components).
> this means the static part of boost::thread is multiple times present in
> the process.
>
> on macos (apple clang 7.3) we see rare (but reproducible) access
> violations caused by boost::thread_specific_ptr::get() unexpectedly
> returning nullptr. if we enable assertions we get an assert in
> thread.cpp:151
>
> if we dynamically link boost the problems go away. i can superficially
> understand that linking only one "common" instanceof boost::thread is
> "more safe".

As Niall said, the general rules for library interaction are to not do that.

You can sometimes get away with it if you're very careful about 
isolation -- in this case, it would probably work if you made sure that 
the thread_specific_ptrs are only ever accessed on threads that were 
started by the same library, and completely hid these threads from the 
consumers of the library -- but this way lies dragons, and it's far too 
easy to make seemingly simple changes that poke a hole in the isolation 
and break things, sometimes in subtle ways.  So don't do it.