Implement DAP breakpointLocations request

This implements the DAP breakpointLocations request.

gdb/data-directory/Makefile.in

@@ -96,6 +96,7 @@ PYTHON_FILE_LIST = \
 	gdb/dap/__init__.py \
 	gdb/dap/io.py \
 	gdb/dap/launch.py \
+	gdb/dap/locations.py \
 	gdb/dap/memory.py \
 	gdb/dap/next.py \
 	gdb/dap/pause.py \

gdb/python/lib/gdb/dap/__init__.py

@@ -25,6 +25,7 @@ from . import bt
 from . import disassemble
 from . import evaluate
 from . import launch
+from . import locations
 from . import memory
 from . import next
 from . import pause

gdb/python/lib/gdb/dap/locations.py

@@ -0,0 +1,45 @@
+# Copyright 2023 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/>.
+
+import gdb
+
+# This is deprecated in 3.9, but required in older versions.
+from typing import Optional
+
+from .server import request
+from .startup import in_gdb_thread, send_gdb_with_response
+
+
+@in_gdb_thread
+def _find_lines(filename, start_line, end_line):
+    lines = set()
+    for entry in gdb.execute_mi("-symbol-list-lines", filename)["lines"]:
+        line = entry["line"]
+        if line >= start_line and line <= end_line:
+            lines.add(line)
+    return {"breakpoints": [{"line": x} for x in sorted(lines)]}
+
+
+@request("breakpointLocations")
+def breakpoint_locations(*, source, line: int, endLine: Optional[int] = None, **extra):
+    if endLine is None:
+        endLine = line
+    if "path" in source:
+        filename = source["path"]
+    elif "name" in source:
+        filename = source["name"]
+    else:
+        raise Exception("")
+    return send_gdb_with_response(lambda: _find_lines(filename, line, endLine))

gdb/testsuite/gdb.dap/basic-dap.c

@@ -38,7 +38,7 @@ address_breakpoint_here ()
 int
 line_breakpoint_here ()
 {
-  do_not_stop_here ();
+  do_not_stop_here ();		/* FIRST */
   function_breakpoint_here ();
   address_breakpoint_here ();
   return 0;			/* BREAK */

gdb/testsuite/gdb.dap/basic-dap.exp

@@ -71,6 +71,21 @@ if {!$ok} {
     fail "check new breakpoint event"
 }
 
+# Check that there are breakpoint locations on each line between FIRST
+# and BREAK.
+set first_line [gdb_get_line_number "FIRST"]
+set last_line [expr {$line - 1}]
+set obj [dap_check_request_and_response "breakpoint locations" \
+	     breakpointLocations \
+	     [format {o source [o path [%s]] line [i %d] endLine [i %d]} \
+		  [list s $srcfile] $first_line $last_line]]
+# We know gdb returns the lines in sorted order.
+foreach entry [dict get [lindex $obj 0] body breakpoints] {
+    gdb_assert {[dict get $entry line] == $first_line} \
+	"line $first_line in result"
+    incr first_line
+}
+
 set obj [dap_check_request_and_response "reset breakpoint by line number" \
 	     setBreakpoints \
 	     [format {o source [o path [%s]] breakpoints [a [o line [i %d]]]} \