Re: RFC: libc6 policy supplement 2nd try

[Rob Browning <rlb@cs.utexas.edu>]

Helmut Geyer <Helmut.Geyer@IWR.Uni-Heidelberg.De> writes:

>     - compile the library using -D_RENTRANT or -D_THREAD_SAFE

There was some talk about adding -D_REENTRANT to the list of flags
that are automatically included by gcc/g++.  I don't recall what the
resulting decision was, if there was one.

>     - there may be no permanent data residing in the library memory that
>       can be different for different threads.
>       this means in the first place no static or global variables that
>       are not in some way protected from access by a different threads.
>     - all write access to files from a library must be both protected
>       using some file locking mechanism in addition to using mutexes.
>     - library functions must be protected from being used at the same
>       time by two threads sharing the same memory space. This is done
>       using mutexes. 

In the general case, I'm not sure it's realistic to expect *all*
libraries to be rewritten thread safe (though it would be nice).  At
the least, though, we should make certain that -D_REENTRANT is always
used, and that it's at least safe to call a given library function if
you make sure only one thread is in the library at a time.  That
should be easier to accomplish.

>    There will be a list available that lists all libraries part of
>    Debian and their current status regarding compliance with these
>    standard requirements. This list will be posted regularly to
>    debian-devel by Helmut Geyer <Helmut.Geyer@iwr.uni-heidelberg.de>.    

This is a good idea.

-- 
Rob


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