Handle DAP evaluate request without a frame ID

DAP specifies that if an evaluate request does not have a frameID
parameter, then the expression is evaluated in the global scope.

gdb/python/lib/gdb/dap/evaluate.py

@@ -30,10 +30,12 @@ class EvaluateResult(VariableReference):
 # Helper function to evaluate an expression in a certain frame.
 @in_gdb_thread
 def _evaluate(expr, frame_id):
+    global_context = True
     if frame_id is not None:
         frame = frame_for_id(frame_id)
         frame.select()
-    val = gdb.parse_and_eval(expr)
+        global_context = False
+    val = gdb.parse_and_eval(expr, global_context=global_context)
     ref = EvaluateResult(val)
     return ref.to_object()
 

gdb/testsuite/gdb.dap/frameless.c

@@ -0,0 +1,24 @@
+/* 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 variable = 23;
+
+int main ()
+{
+  int variable = 97;
+  return 0;			/* BREAK */
+}

gdb/testsuite/gdb.dap/frameless.exp

@@ -0,0 +1,62 @@
+# 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/>.
+
+# Test frameless evaluation in DAP.
+
+require allow_dap_tests
+
+load_lib dap-support.exp
+
+standard_testfile
+
+if {[build_executable ${testfile}.exp $testfile] == -1} {
+    return
+}
+
+if {[dap_launch $testfile] == ""} {
+    return
+}
+
+set line [gdb_get_line_number "BREAK"]
+set obj [dap_check_request_and_response "set breakpoint by line number" \
+	     setBreakpoints \
+	     [format {o source [o path [%s]] breakpoints [a [o line [i %d]]]} \
+		  [list s $srcfile] $line]]
+set line_bpno [dap_get_breakpoint_number $obj]
+
+dap_check_request_and_response "start inferior" configurationDone
+dap_wait_for_event_and_check "inferior started" thread "body reason" started
+
+dap_wait_for_event_and_check "stopped at line breakpoint" stopped \
+    "body reason" breakpoint \
+    "body hitBreakpointIds" $line_bpno
+
+set bt [lindex [dap_check_request_and_response "backtrace" stackTrace \
+		    {o threadId [i 1]}] \
+	    0]
+set frame_id [dict get [lindex [dict get $bt body stackFrames] 0] id]
+
+set obj [dap_check_request_and_response "evaluate variable in function" \
+	     evaluate [format {o expression [s variable] frameId [i %s]} \
+			   $frame_id]]
+dap_match_values "variable value in function" [lindex $obj 0] \
+    "body result" 97
+
+set obj [dap_check_request_and_response "evaluate variable globally" \
+	     evaluate {o expression [s variable]}]
+dap_match_values "variable value globally" [lindex $obj 0] \
+    "body result" 23
+
+dap_shutdown