New GDB/MI command "-info-gdb-mi-command"

This patch adds a new GDB/MI command meant for graphical frontends
trying to determine whether a given GDB/MI command exists or not.

Examples:

    -info-gdb-mi-command unsupported-command
    ^done,command={exists="false"}
    (gdb)
    -info-gdb-mi-command symbol-list-lines
    ^done,command={exists="true"}
    (gdb)

At the moment, this is the only piece of information that this
command returns.

Eventually, and if needed, we can extend it to provide
command-specific pieces of information, such as updates to
the command's syntax since inception.  This could become,
for instance:

    -info-gdb-mi-command symbol-list-lines
    ^done,command={exists="true",features=[]}
    (gdb)
    -info-gdb-mi-command catch-assert
    ^done,command={exists="true",features=["conditions"]}

In the first case, it would mean that no extra features,
while in the second, it announces that the -catch-assert
command in this version of the debugger supports a feature
called "condition" - exact semantics to be documented with
combined with the rest of the queried command's documentation.

But for now, we start small, and only worry about existance.
And to bootstrap the process, I have added an entry in the
output of the -list-features command as well ("info-gdb-mi-command"),
allowing the graphical frontends to go through the following process:

  1. Send -list-features, collect info from there as before;
  2. Check if the output contains "info-gdb-mi-command".
     If it does, then support for various commands can be
     queried though -info-gdb-mi-command. Newer commands
     will be expected to always be checked via this new
     -info-gdb-mi-command.

gdb/ChangeLog:

        * mi/mi-cmds.h (mi_cmd_info_gdb_mi_command): Declare.
        * mi/mi-cmd-info.c (mi_cmd_info_gdb_mi_command): New function.
        * mi/mi-cmds.c (mi_cmds): Add -info-gdb-mi-command command.
        * mi/mi-main.c (mi_cmd_list_features): Add "info-gdb-mi-command"
        field to output of "-list-features".

        * NEWS: Add entry for new -info-gdb-mi-command.

gdb/doc/ChangeLog:

        * gdb.texinfo (GDB/MI Miscellaneous Commands): Document
        the new -info-gdb-mi-command GDB/MI command.  Document
        the meaning of "-info-gdb-mi-command" in the output of
        -list-features.

gdb/testsuite/ChangeLog:

        * gdb.mi/mi-i-cmd.exp: New file.

2 files changed, 50 insertions, 0 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 8be246d..43a7c67 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2013-12-03  Joel Brobecker  <brobecker@adacore.com>
+
+	* gdb.mi/mi-i-cmd.exp: New file.
+
 2013-12-02  Doug Evans  <dje@google.com>
 
 	* gdb.dwarf/dwp-symlink.c: Fake out gdb to not load debug info
diff --git a/gdb/testsuite/gdb.mi/mi-i-cmd.exp b/gdb/testsuite/gdb.mi/mi-i-cmd.exp
new file mode 100644
index 0000000..802f1ab
--- /dev/null
+++ b/gdb/testsuite/gdb.mi/mi-i-cmd.exp
@@ -0,0 +1,46 @@
+# Copyright 2013 Free Software Foundation, Inc.
+
+# 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/>.
+
+load_lib mi-support.exp
+set MIFLAGS "-i=mi"
+
+gdb_exit
+if [mi_gdb_start] {
+    continue
+}
+
+# First, verify that the debugger correctly advertises support
+# for the -info-gdb-mi-command command.
+mi_gdb_test "-list-features" \
+            "\\^done,features=\\\[.*\"info-gdb-mi-command\".*\\\]" \
+            "-list-features includes \"info-gdb-mi-command\""
+
+mi_gdb_test "-info-gdb-mi-command unsupported-command" \
+            "\\^done,command=\\\{exists=\"false\"\\\}" \
+            "-info-gdb-mi-command unsupported-command"
+
+# Same test as above, but including the leading '-' in the command name.
+mi_gdb_test "-info-gdb-mi-command -unsupported-command" \
+            "\\^done,command=\\\{exists=\"false\"\\\}" \
+            "-info-gdb-mi-command -unsupported-command"
+
+mi_gdb_test "-info-gdb-mi-command symbol-list-lines" \
+            "\\^done,command=\\\{exists=\"true\"\\\}" \
+            "-info-gdb-mi-command symbol-list-lines"
+
+# Same test as above, but including the leading '-' in the command name.
+mi_gdb_test "-info-gdb-mi-command -symbol-list-lines" \
+            "\\^done,command=\\\{exists=\"true\"\\\}" \
+            "-info-gdb-mi-command -symbol-list-lines"