Always propagate exceptions in DAP

This changes the DAP exec_and_log function to always transform an
exception into a DAPException and propagate it.

As the bug points out, we haven't always wrapped calls when
appropriate.  I think it's better to cause the request to fail by
default; if any spot truly needs to ignore errors, that is readily
done at the point of call.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=33346

gdb/python/lib/gdb/dap/events.py

@@ -161,7 +161,7 @@ _expected_pause = False
 
 
 @in_gdb_thread
-def exec_and_expect_stop(cmd, expected_pause=False, propagate_exception=False):
+def exec_and_expect_stop(cmd, expected_pause=False):
     """A wrapper for exec_and_log that sets the continue-suppression flag.
 
     When EXPECTED_PAUSE is True, a stop that looks like a pause (e.g.,
@@ -174,7 +174,7 @@ def exec_and_expect_stop(cmd, expected_pause=False, propagate_exception=False):
     # continuing.
     _suppress_cont = not expected_pause
     # FIXME if the call fails should we clear _suppress_cont?
-    exec_and_log(cmd, propagate_exception)
+    exec_and_log(cmd)
 
 
 # Map from gdb stop reasons to DAP stop reasons.  Some of these can't

gdb/python/lib/gdb/dap/next.py

@@ -76,7 +76,7 @@ def step_in(
 @request("stepOut")
 def step_out(*, threadId: int, singleThread: bool = False, **args):
     _handle_thread_step(threadId, singleThread, True)
-    exec_and_expect_stop("finish &", propagate_exception=True)
+    exec_and_expect_stop("finish &")
 
 
 @request("continue")

gdb/python/lib/gdb/dap/startup.py

@@ -204,7 +204,7 @@ def log_stack(level=LogLevel.DEFAULT):
 
 
 @in_gdb_thread
-def exec_and_log(cmd, propagate_exception=False):
+def exec_and_log(cmd):
     """Execute the gdb command CMD.
     If logging is enabled, log the command and its output."""
     log("+++ " + cmd)
@@ -213,10 +213,10 @@ def exec_and_log(cmd, propagate_exception=False):
         if output != "":
             log(">>> " + output)
     except gdb.error as e:
-        if propagate_exception:
-            raise DAPException(str(e)) from e
-        else:
-            log_stack()
+        # Don't normally want to see this, as it interferes with the
+        # test suite.
+        log_stack(LogLevel.FULL)
+        raise DAPException(str(e)) from e
 
 
 @in_gdb_thread

gdb/testsuite/gdb.dap/attach-fail.exp

@@ -0,0 +1,32 @@
+# Copyright 2025 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 "attach" failure in DAP.
+
+require can_spawn_for_attach allow_dap_tests
+
+load_lib dap-support.exp
+
+# Passing an empty remote name here will guarantee a failure without
+# trying to find a real remote.
+set id [dap_target_remote {""}]
+
+dap_check_request_and_response "configurationDone" configurationDone
+
+set resp [lindex [dap_read_response attach $id] 0]
+gdb_assert {[dict get $resp success] == "false"} \
+    "attach failed"
+
+dap_shutdown