[PATCH] Fix DAP stackTrace through frames without debuginfo

[Tom Tromey <tromey@adacore.com>]

The DAP stackTrace implementation did not fully account for frames
without debuginfo.  Attemping this would yield a result like:

{"request_seq": 5, "type": "response", "command": "stackTrace", "success": false, "message": "'NoneType' object has no attribute 'filename'", "seq": 11}

This patch fixes the problem by adding another check for None.
---
 gdb/python/lib/gdb/dap/bt.py         |  4 +--
 gdb/testsuite/gdb.dap/bt-inner.c     | 24 ++++++++++++++
 gdb/testsuite/gdb.dap/bt-main.c      | 29 +++++++++++++++++
 gdb/testsuite/gdb.dap/bt-nodebug.exp | 47 ++++++++++++++++++++++++++++
 4 files changed, 102 insertions(+), 2 deletions(-)
 create mode 100644 gdb/testsuite/gdb.dap/bt-inner.c
 create mode 100644 gdb/testsuite/gdb.dap/bt-main.c
 create mode 100644 gdb/testsuite/gdb.dap/bt-nodebug.exp

diff --git a/gdb/python/lib/gdb/dap/bt.py b/gdb/python/lib/gdb/dap/bt.py
index 990ab135b05..01d1aa088e2 100644
--- a/gdb/python/lib/gdb/dap/bt.py
+++ b/gdb/python/lib/gdb/dap/bt.py
@@ -1,4 +1,4 @@
-# Copyright 2022 Free Software Foundation, Inc.
+# Copyright 2022, 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
@@ -69,7 +69,7 @@ def _backtrace(thread_id, levels, startFrame):
                 "instructionPointerReference": hex(current_frame.pc()),
             }
             sal = _safe_sal(current_frame)
-            if sal is not None:
+            if sal is not None and sal.symtab is not None:
                 newframe["source"] = {
                     "name": os.path.basename(sal.symtab.filename),
                     "path": sal.symtab.filename,
diff --git a/gdb/testsuite/gdb.dap/bt-inner.c b/gdb/testsuite/gdb.dap/bt-inner.c
new file mode 100644
index 00000000000..f5d48ab128e
--- /dev/null
+++ b/gdb/testsuite/gdb.dap/bt-inner.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/>.  */
+
+extern void function_breakpoint_here (void);
+
+void
+no_debug_info (void)
+{
+  function_breakpoint_here ();
+}
diff --git a/gdb/testsuite/gdb.dap/bt-main.c b/gdb/testsuite/gdb.dap/bt-main.c
new file mode 100644
index 00000000000..7664ef79932
--- /dev/null
+++ b/gdb/testsuite/gdb.dap/bt-main.c
@@ -0,0 +1,29 @@
+/* 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/>.  */
+
+extern void no_debug_info (void);
+
+void
+function_breakpoint_here (void)
+{
+}
+
+int main ()
+{
+  no_debug_info ();
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.dap/bt-nodebug.exp b/gdb/testsuite/gdb.dap/bt-nodebug.exp
new file mode 100644
index 00000000000..e365f0877d4
--- /dev/null
+++ b/gdb/testsuite/gdb.dap/bt-nodebug.exp
@@ -0,0 +1,47 @@
+# 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 DAP 'bt' through a function without debuginfo.
+
+load_lib dap-support.exp
+
+standard_testfile bt-main.c bt-inner.c
+
+if {[build_executable_from_specs $testfile.exp $testfile {} \
+	 $srcfile debug \
+	 $srcfile2 {}] == -1} {
+    return
+}
+
+if {[dap_launch $testfile] == ""} {
+    return
+}
+
+set obj [dap_check_request_and_response "set breakpoint on inner" \
+	     setFunctionBreakpoints \
+	     {o breakpoints [a [o name [s function_breakpoint_here]]]}]
+set fn_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
+
+lassign [dap_wait_for_event_and_check "stopped at function breakpoint" stopped \
+	    "body reason" breakpoint \
+	    "body hitBreakpointIds" $fn_bpno] unused objs
+
+# The bug was that this request would fail.
+dap_check_request_and_response "backtrace" stackTrace {o threadId [i 1]}
+
+dap_shutdown
-- 
2.39.1