[Bug libstdc++/51701] New: Remove reference to Henry Suter's RWLock from documentation

["jb at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51701

             Bug #: 51701
           Summary: Remove reference to Henry Suter's RWLock from
                    documentation
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jb@gcc.gnu.org


In the libstdc++ manual at

http://gcc.gnu.org/onlinedocs/libstdc++/manual/ext_io.html

it says "If you want to access a filebuf's file descriptor to implement file
locking (e.g. using the fcntl() system call) then you might be interested in
Henry Suter's RWLock class. "

There are a couple issues with this RWLock class:

- The code has apparently disappeared from the internet, I was able to locate
it only via the Wayback machine.

- Having looked at the code, it is racy and wrong: 

1) For the code to operate correctly, opening a file and reading and writing
stuff from that file would need to be atomic. No target I'm aware of provides
such a guarantee.

2) It leaks memory; RWLockFileName is not deleted in the destructor.


Thus, I suggest that the sentence I quoted above should be removed.