Implement DAP "hover" context

A DAP client can request that an expression be evaluated in "hover"
context, meaning that it should not cause side effects.  In gdb, this
can be implemented by temporarily setting a few "may-" parameters to
"off".

In order to make this work, I had to also change "may-write-registers"
so that it can be changed while the program is running.  I don't think
there was any reason for this prohibition in the first place.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30476

1 files changed, 30 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.dap/hover.c b/gdb/testsuite/gdb.dap/hover.c
new file mode 100644
index 0000000..f853396
--- /dev/null
+++ b/gdb/testsuite/gdb.dap/hover.c
@@ -0,0 +1,30 @@
+/* Copyright 2023 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+int global_variable = 23;
+
+int
+increment ()
+{
+  return ++global_variable;
+}
+
+int
+main ()
+{
+  return 0; 			/* BREAK */
+}