gdb/mi: fix breakpoint script field output

The "script" field, output whenever information about a breakpoint with
commands is output, uses wrong MI syntax.

    $ ./gdb -nx -q --data-directory=data-directory -x script -i mi
    =thread-group-added,id="i1"
    =breakpoint-created,bkpt={number="1",type="breakpoint",disp="keep",enabled="y",addr="0x000000000000111d",func="main",file="test.c",fullname="/home/simark/build/binutils-gdb-one-target/gdb/test.c",line="3",thread-groups=["i1"],times="0",original-location="main"}
    =breakpoint-modified,bkpt={number="1",type="breakpoint",disp="keep",enabled="y",addr="0x000000000000111d",func="main",file="test.c",fullname="/home/simark/build/binutils-gdb-one-target/gdb/test.c",line="3",thread-groups=["i1"],times="0",script={"aaa","bbb","ccc"},original-location="main"}
    (gdb)
    -break-info
    ^done,BreakpointTable={nr_rows="1",nr_cols="6",hdr=[{width="7",alignment="-1",col_name="number",colhdr="Num"},{width="14",alignment="-1",col_name="type",colhdr="Type"},{width="4",alignment="-1",col_name="disp",colhdr="Disp"},{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},{width="18",alignment="-1",col_name="addr",colhdr="Address"},{width="40",alignment="2",col_name="what",colhdr="What"}],body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",addr="0x000000000000111d",func="main",file="test.c",fullname="/home/simark/build/binutils-gdb-one-target/gdb/test.c",line="3",thread-groups=["i1"],times="0",script={"aaa","bbb","ccc"},original-location="main"}]}
    (gdb)

In both the =breakpoint-modified and -break-info output, we have:

     script={"aaa","bbb","ccc"}

According to the output syntax [1], curly braces means tuple, and a
tuple contains key=value pairs.  This looks like it should be a list,
but uses curly braces by mistake.  This would make more sense:

    script=["aaa","bbb","ccc"]

Fix it, keeping the backwards compatibility by introducing a new MI
version (MI4), in exactly the same way as was done when fixing
multi-locations breakpoint output in [2].

 - Add a fix_breakpoint_script_output uiout flag.  MI uiouts will use
   this flag if the version is >= 4.
 - Add a fix_breakpoint_script_output_globally variable and the
   -fix-breakpoint-script-output MI command to set it, if frontends want
   to use the fixed output for this without using the newer MI version.
 - When emitting the script field, use list instead of tuple, if we want
   the fixed output (depending on the two criteria above)
 -

[1] https://sourceware.org/gdb/onlinedocs/gdb/GDB_002fMI-Output-Syntax.html#GDB_002fMI-Output-Syntax
[2] https://gitlab.com/gnutools/binutils-gdb/-/commit/b4be1b0648608a2578bbed39841c8ee411773edd

Change-Id: I7113c6892832c8d6805badb06ce42496677e2242
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=24285

3 files changed, 121 insertions, 1 deletions

diff --git a/gdb/testsuite/gdb.mi/mi-breakpoint-changed.exp b/gdb/testsuite/gdb.mi/mi-breakpoint-changed.exp
index 6472dcd..b71ea35 100644
--- a/gdb/testsuite/gdb.mi/mi-breakpoint-changed.exp
+++ b/gdb/testsuite/gdb.mi/mi-breakpoint-changed.exp
@@ -97,7 +97,7 @@ proc test_insert_delete_modify { } {
 	$test
     set test "dprintf marker, \"arg\" \""
     mi_gdb_test $test \
-	{.*=breakpoint-created,bkpt=\{number="6",type="dprintf".*,script=\{\"printf \\\"arg\\\" \\\"\"\}.*\}\r\n\^done} \
+	{.*=breakpoint-created,bkpt=\{number="6",type="dprintf".*,script=\[\"printf \\\"arg\\\" \\\"\"\].*\}\r\n\^done} \
 	$test
 
     # 2. when modifying condition
diff --git a/gdb/testsuite/gdb.mi/mi-breakpoint-script.c b/gdb/testsuite/gdb.mi/mi-breakpoint-script.c
new file mode 100644
index 0000000..6b3984d
--- /dev/null
+++ b/gdb/testsuite/gdb.mi/mi-breakpoint-script.c
@@ -0,0 +1,22 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2022 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/>.  */
+
+int
+main (void)
+{
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.mi/mi-breakpoint-script.exp b/gdb/testsuite/gdb.mi/mi-breakpoint-script.exp
new file mode 100644
index 0000000..ddf0be1
--- /dev/null
+++ b/gdb/testsuite/gdb.mi/mi-breakpoint-script.exp
@@ -0,0 +1,98 @@
+# Copyright 2022 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/>.
+
+# Tests the breakpoint script field, including the wrong syntax that GDB
+# emitted before version 13.1.
+
+load_lib mi-support.exp
+standard_testfile .c
+
+if {[gdb_compile "$srcdir/$subdir/$srcfile" $binfile executable {debug}] != "" } {
+    return -1
+}
+
+# Generate the regexp pattern used to match the breakpoint description emitted
+# in the various breakpoint command results/events.
+#
+# - EXPECT_FIXED_OUTPUT: If true, expect GDB to output the fixed output for the
+#   script field, else expect it to output the broken pre-mi4 format.
+
+proc make_pattern { expect_fixed_output } {
+    if $expect_fixed_output {
+	return "bkpt=\{number=\"${::decimal}\",type=\"breakpoint\",.*,script=\\\[\"abc\",\"def\"\\\],.*"
+    } else {
+	return "bkpt=\{number=\"${::decimal}\",type=\"breakpoint\",.*,script=\\\{\"abc\",\"def\"\\\},.*"
+    }
+}
+
+# Run the test with the following parameters:
+#
+# - MI_VERSION: the version of the MI interpreter to use (e.g. "2")
+# - USE_FIX_FLAG: Whether to issue the -fix-breakpoint-script-output
+#   command after starting GDB
+# - EXPECT_FIXED_OUTPUT: If true, expect GDB to output the fixed output for the
+#   script field, else expect it to output the broken pre-mi4 format.
+
+proc do_test { mi_version use_fix_flag expect_fixed_output } {
+    with_test_prefix "mi_version=${mi_version}" {
+	with_test_prefix "use_fix_flag=${use_fix_flag}" {
+	    save_vars { ::MIFLAGS } {
+		set ::MIFLAGS "-i=mi${mi_version}"
+
+		mi_clean_restart $::binfile
+	    }
+
+	    if $use_fix_flag {
+		mi_gdb_test "-fix-breakpoint-script-output" "\\^done" \
+		    "send -fix-multi-location-breakpoint-output"
+	    }
+
+            # Create a breakpoint.
+	    mi_gdb_test "-break-insert main" ".*" "add breakpoint on main"
+
+            set pattern [make_pattern $expect_fixed_output]
+
+            # Add commands.  Use the CLI command, so we can verify the
+            # =breakpoint-modified output.
+            mi_gdb_test "commands\nabc\ndef\nend" ".*=breakpoint-modified,$pattern\r\n\\^done" "add breakpoint commands"
+
+	    # Check the -break-info output.
+	    mi_gdb_test "-break-info" \
+		"\\^done,BreakpointTable=.*${pattern}" \
+		"-break-info"
+
+	    mi_gdb_exit
+	}
+    }
+}
+
+# Vanilla mi3
+do_test 3 0 0
+
+# mi3 with -fix-breakpoint-script-output
+do_test 3 1 1
+
+# Vanilla mi4
+do_test 4 0 1
+
+# mi4 with -fix-breakpoint-script-output
+do_test 4 1 1
+
+# Whatever MI version is currently the default one, vanilla
+do_test "" 0 1
+
+# Whatever MI version is currently the default one, with
+# -fix-breakpoint-script-output
+do_test "" 1 1