Remove several race conditions with signal handler (bug #61370). This patch removes several race conditions between the interpreter and the Ctrl-C signal handler, as described in more detail in bug #61370. * libinterp/corefcn/sighandlers.h: Make can_interrupt atomic. * libinterp/corefcn/sighandlers.cc: Make can_interrupt, signals_caught atomic, use atomic value read for signals_caught, octave_interrupt_state, change 1 to true. * liboctave/util/quit.h: Move octave_interrupt_state and octave_signal_caught to C++ only code, rewrite octave_quit() function, rewrite OCTAVE_QUIT macro to use octave_quit_c() function. * liboctave/util/quit.cc: Make octave_interrupt_state and octave_signal_caught atomic, add new wrapper function octave_quit_c(). * libinterp/corefcn/interpreter.h: Make octave_initialized atomic. * libinterp/corefcn/interpreter.cc: Make octave_initialized atomic, change 0 to false. * liboctave/util/action-container.h: New namespace "util", make m_val atomic. * liboctave/util/oct-atomic.c: Reorder preprocessor if-elif-else ladder. * liboctave/util/cmd-edit.cc: Change 0 to false.

--- a/libinterp/corefcn/interpreter.cc	Sat Dec 03 13:55:14 2022 +0100
+++ b/libinterp/corefcn/interpreter.cc	Sat Dec 03 10:36:59 2022 -0500
@@ -91,7 +91,7 @@
 bool octave_interpreter_ready = false;
 
 // TRUE means we've processed all the init code and we are good to go.
-bool octave_initialized = false;
+std::atomic<bool> octave_initialized{false};
 
 OCTAVE_BEGIN_NAMESPACE(octave)
 
@@ -1950,7 +1950,7 @@
 
   can_interrupt = true;
   octave_interrupt_state = 0;
-  octave_signal_caught = 0;
+  octave_signal_caught = false;
   octave_restore_signal_mask ();
   catch_interrupts ();
 }