Document pseudo-terminal and interrupting changesusers/palves/ctrl-c

This documents changes done in previous patches:

 - the fact that on GNU/Linux, GDB creates a pseudo-terminal for the
   inferior instead of juggling terminal settings.

 - That when the inferior and GDB share the terminal, you can't
   interrupt some programs with Ctrl-C.

 - That on GNU/Linux, you may get "Program stopped." instead of
   "Program received SIGINT" in response to Ctrl-C.

 - That run+detach may result in the program dying with SIGHUP.

I was surprised that we do not currently have a node/section
specifically to talk about interrupting programs.  Thus I've added a
new "Interrupting" section under the "Stopping and Continuing"
chapter, with some xrefs to other sections.

gdb/ChangeLog:
yyyy-mm-dd  Pedro Alves  <pedro@palves.net>

	* NEWS: Document pseudo-terminal, "tty /dev/tty" and Ctrl-C/SIGINT
	changes.  Document "set/show debug managed-tty".

gdb/doc/ChangeLog:
yyyy-mm-dd  Pedro Alves  <pedro@palves.net>

	* gdb.texinfo (Input/Output): Document that GDB may start a
	program associated with a pseudo-terminal.  Document "tty
	/dev/tty".  Document "set/show debug managed-tty".
	(Attach): Document what happens on run+detach on systems where GDB
	creates a pseudo-terminal for the inferior.
	(Stopping and Continuing): Add new Interrupting node.
	(Background Execution): Add anchor.
	(Features for Debugging MS Windows PE Executables): Add anchor.

Change-Id: I267a0f9300c7ac4d2e7f14a9ba8eabc1eafcc5a7

1 files changed, 23 insertions, 0 deletions

diff --git a/gdb/NEWS b/gdb/NEWS
index 56743fc..90361d3 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -6,6 +6,25 @@
 * The 'set disassembler-options' command now supports specifying options
   for the ARC target.
 
+* On GNU/Linux, by default GDB now starts programs associated with a
+  pseudo-terminal slave device created and managed by GDB, instead of
+  having the inferior use the same terminal as GDB directly.  GDB
+  takes care of forwarding input and output to and from GDB's terminal
+  at appropriate times, so this is largely transparent.
+
+  In addition, by default, Ctrl-C no longer stops the program with
+  SIGINT.  Instead you'll see for example:
+
+     Thread 1 "main" stopped.
+
+  With these changes it is now possible to interrupt programs that
+  block or ignore the SIGINT signal (with e.g., the sigprocmask
+  function), or use the sigwait function to wait for SIGINT signal.
+
+  You can use the "tty /dev/tty" command to restore the previous
+  behavior of spawning programs associated with the same terminal as
+  GDB.
+
 * GDB now supports general memory tagging functionality if the underlying
   architecture supports the proper primitives and hooks.  Currently this is
   enabled only for AArch64 MTE.
@@ -84,6 +103,10 @@ set debug event-loop
 show debug event-loop
   Control the display of debug output about GDB's event loop.
 
+set debug managed-tty
+show debug managed-tty
+  Control the display of debug output about GDB-managed terminals.
+
 set print memory-tag-violations
 show print memory-tag-violations
   Control whether to display additional information about memory tag violations