Refactor to avoid nonnull checks on "this" pointer.

G++ 6.0 asserts that the "this" pointer is non-null for member
functions.
Refactor methods that check if "this" is non-null to resolve this.

winsup/cygwin/ChangeLog:
external.cc (cygwin_internal): Check for a null pinfo before calling
cmdline.
fhandler_dsp.cc (Audio::blockSize): Make static.
fhandler_dsp.cc (Audio_in): add default_buf_info.
fhandler_dsp.cc (Audio_out): Ditto.
fhandler_dsp.cc (Audio_out::buf_info): Refactor method to call
default_buf_info if dev_ is null.
fhandler_dsp.cc (Audio_in::buf_info): Ditto.
fhandler_dsp.cc (fhandler_dev_dsp::_ioctl): Call Audio_out::default_buf_info if audio_out_ is null.
fhandler_dsp.cc (fhandler_dev_dsp::_ioctl): Call Audio_in::default_buf_info if audio_in_ is null.
fhandler_process.cc (format_process_fd): Check if pinfo is null.
fhandler_process.cc (format_process_root): Ditto.
fhandler_process.cc (format_process_cwd): Ditto.
fhandler_process.cc (format_process_cmdline): Ditto.
signal.cc (tty_min::kill_pgrp): Ditto.
signal.cc (_pinfo::kill0): Ditto.
sigproc.cc (pid_exists): Ditto.
sigproc.cc (remove_proc): Ditto.
times.cc (clock_gettime): Ditto.
times.cc (clock_getcpuclockid): Ditto.
path.cc (cwdstuff::override_win32_cwd): Check if old_cwd is null.
path.cc (fcwd_access_t::Free): Factor null check of "this" out to
caller(s).
pinfo.cc (_pinfo::exists): Ditto.
pinfo.cc (_pinfo::fd): Ditto.
pinfo.cc (_pinfo::fds): Ditto.
pinfo.cc (_pinfo::root): Ditto.
pinfo.cc (_pinfo::cwd): Ditto.
pinfo.cc (_pinfo::cmdline): Ditto.
signal.cc (_pinfo::kill): Ditto.
pinfo.cc (_pinfo::commune_request): remove non-null check on "this", as
this method is only called from pinfo.cc after null checks
pinfo.cc (_pinfo::pipe_fhandler): remove non-null check on "this", as
this method is only called from pipe.cc (fhandler_pipe::open) after a null check.

Signed-off-by: Peter Foley <pefoley2@pefoley.com>

winsup/cygwin/external.cc

@@ -342,7 +342,7 @@ cygwin_internal (cygwin_getinfo_types t, ...)
 	  size_t n;
 	  pid_t pid = va_arg (arg, pid_t);
 	  pinfo p (pid);
-	  res = (uintptr_t) p->cmdline (n);
+	  res = p ? (uintptr_t) p->cmdline (n) : 0;
 	}
 	break;
       case CW_CHECK_NTSEC: