Re: [RFC] gdb/testsuite/gdb.base/fileio.exp patch for cygwin

[Pedro Alves <pedro_alves at portugalmail dot pt>]

Corinna Vinschen wrote:
> Right.  The problem occurs when running a session in a pseudo tty like
> when starting GDB in a ssh session or when you set CYGWIN=tty before
> starting the first Cygwin process (the shell, usually) in a Windows
> console window.
>
> Pseudo ttys are implemented in Cygwin using pipes.  When you start a
> Cygwin application with fork/exec, the knowledge about this pipes (being
> a pseudo tty) is inherited by the child process by means of the fork/
> exec magic.
>
> If you start a Cygwin process from another application using native
> Windows functions (CreateProcess, etc), the whole fork/exec magic is
> missing, apparently.  One result is that the child process has to
> figure out what the stdin/out/err streams are, using native Windows
> functions.  Since native Windows functions have no idea what a pseudo
> tty is, the information returned is that stdio streams are connected
> to pipes.  So the child thinks its stdio streams are just pipes and
> pipes are not ttys, apparently.

Thank you very much for the explanation.

Isn't there a shared memory section amongst all loaded
copies of cygwin1.dll?  Can't that be used to reconstruct
the pseudo ttys from the pipes?

--
Pedro Alves