[PATCH 3/6] Introduce gdb.interrupt

[Tom Tromey <tromey@adacore.com>]

DAP cancellation needs a way to interrupt whatever is happening on
gdb's main thread -- whether that is the inferior, a gdb CLI command,
or Python code.

This patch adds a new gdb.interrupt() function for this purpose.  It
simply sets the quit flag and lets gdb do the rest.

No tests in this patch -- instead this is tested via the DAP
cancellation tests.
---
 gdb/NEWS            |  2 ++
 gdb/doc/python.texi | 11 +++++++++++
 gdb/python/python.c | 19 +++++++++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/gdb/NEWS b/gdb/NEWS
index 1073e38dfc6..0c44f0253f6 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -57,6 +57,8 @@ show remote thread-options-packet
      sub-classed to create handlers for objfiles with missing debug
      information.
 
+  ** New function gdb.interrupt(), that interrupts GDB's main thread.
+
 * New remote packets
 
 New stop reason: clone
diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
index b65991bbad0..7d6b7e82edb 100644
--- a/gdb/doc/python.texi
+++ b/gdb/doc/python.texi
@@ -664,6 +664,17 @@ this an easy-to-use drop-in replacement for creating threads that will
 work well in @value{GDBN}.
 @end deftp
 
+@defun gdb.interrupt ()
+This causes the main thread of @value{GDBN} to react as if the user
+had typed a control-C character at the terminal.  That is, if the
+inferior is running, it is interrupted; if a @value{GDBN} command is
+executing, it is stopped; and if a Python command is running,
+@code{KeyboardInterrupt} will be raised.
+
+Unlike most Python APIs in @value{GDBN}, @code{interrupt} is
+thread-safe.
+@end defun
+
 @defun gdb.post_event (event)
 Put @var{event}, a callable object taking no arguments, into
 @value{GDBN}'s internal event queue.  This callable will be invoked at
diff --git a/gdb/python/python.c b/gdb/python/python.c
index 8a36673a3e4..832f374b39f 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -1118,6 +1118,23 @@ gdbpy_post_event (PyObject *self, PyObject *args)
   Py_RETURN_NONE;
 }
 
+/* Interrupt the current operation on the main thread.  */
+static PyObject *
+gdbpy_interrupt (PyObject *self, PyObject *args)
+{
+  {
+    /* Make sure the interrupt isn't delivered immediately somehow.
+       This probably is not truly needed, but at the same time it
+       seems more clear to be explicit about the intent.  */
+    gdbpy_allow_threads temporarily_exit_python;
+    scoped_disable_cooperative_sigint_handling no_python_sigint;
+
+    set_quit_flag ();
+  }
+
+  Py_RETURN_NONE;
+}
+
 \f
 
 /* This is the extension_language_ops.before_prompt "method".  */
@@ -2678,6 +2695,8 @@ Parse String as an expression, evaluate it, and return the result as a Value."
 
   { "post_event", gdbpy_post_event, METH_VARARGS,
     "Post an event into gdb's event loop." },
+  { "interrupt", gdbpy_interrupt, METH_NOARGS,
+    "Interrupt gdb's current operation." },
 
   { "target_charset", gdbpy_target_charset, METH_NOARGS,
     "target_charset () -> string.\n\

-- 
2.41.0