Re: [PATCH 1/4] [gdb] Add logging_file::fd

[Tom Tromey <tom@tromey.com>]

>>>>> "Tom" == Tom de Vries <tdevries@suse.de> writes:

Tom> Logging_file is derived from ui_file, which defines a virtual fd member
Tom> function:
Tom> ...
Tom>   /* If this object has an underlying file descriptor, then return it.
Tom>      Otherwise, return -1.  */
Tom>   virtual int fd () const
Tom>   { return -1; }
Tom> ...

Tom> Logging_file doesn't define its own fd, so it defaults to -1.

That test in bt-utils.c (and the other one in event-top.c) look weird to
me.  It does this:

  if (gdb_stderr == nullptr || gdb_stderr->fd () == -1)
    std::ignore = ::write (2, msg, strlen (msg));
  else
    gdb_stderr->write_async_safe (msg, strlen (msg));

But why is that -1 check there?

Is it because the default ui_file::write_async_safe aborts?

Since if so then maybe that's the real issue: the API is kind of
incoherent here.

I wonder whether we could simply remove the fd() method entirely and
instead make the default write_async_safe do something sensible; or make
it pure virtual and require the subclasses to DTRT.

Tom