From: Tom Tromey <tromey@adacore.com>
Date: Fri, 19 Dec 2025 12:51:39 +0000 (-0700)
Subject: Change handling of over-long DAP variables requests
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f33058a1fcea5f3b95df38ebcdd0c81b79e5c59e;p=thirdparty%2Fbinutils-gdb.git

Change handling of over-long DAP variables requests

In PR dap/33228, we changed gdb to gracefully report an error if a DAP
'variables' request asked for more variables than had been reported.

This behavior was clarified in the spec, see

    https://github.com/microsoft/debug-adapter-protocol/issues/571

This patch changes gdb to conform to the specified approach, namely
truncating the list rather than erroring.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=33228
Approved-By: Andrew Burgess <aburgess@redhat.com>
---

diff --git a/gdb/python/lib/gdb/dap/varref.py b/gdb/python/lib/gdb/dap/varref.py
index f5ffe34f7f5..e7d114c9d51 100644
--- a/gdb/python/lib/gdb/dap/varref.py
+++ b/gdb/python/lib/gdb/dap/varref.py
@@ -146,10 +146,12 @@ class BaseReference(ABC):
         if self._children is None:
             self._children = [None] * self.child_count()
         for idx in range(start, start + count):
+            # DAP was clarified to say that if too many children are
+            # requested, this is not an error, but instead the result
+            # is just truncated.
+            # https://github.com/microsoft/debug-adapter-protocol/issues/571
             if idx >= len(self._children):
-                raise DAPException(
-                    f"requested child {idx} outside range of variable {self._ref}"
-                )
+                break
             if self._children[idx] is None:
                 (name, value) = self.fetch_one_child(idx)
                 name = self._compute_name(name)
diff --git a/gdb/testsuite/gdb.dap/scopes.exp b/gdb/testsuite/gdb.dap/scopes.exp
index 52efa683c4c..b3026263a90 100644
--- a/gdb/testsuite/gdb.dap/scopes.exp
+++ b/gdb/testsuite/gdb.dap/scopes.exp
@@ -133,12 +133,15 @@ set refs [lindex [dap_check_request_and_response "fetch contents of dei" \
 set deivals [dict get $refs body variables]
 gdb_assert {[llength $deivals] == 2} "dei has two members"
 
-# Request more children than exist.  See PR dap/33228.
-set seq [dap_send_request variables \
-	     [format {o variablesReference [i %d] count [i 100]} $dei_ref]]
-lassign [dap_read_response variables $seq] response ignore
-gdb_assert {[dict get $response success] == "false"} \
-    "variables with invalid count"
+# Request more children than exist.  See PR dap/33228 and
+# https://github.com/microsoft/debug-adapter-protocol/issues/571.
+set refs [lindex [dap_check_request_and_response "fetch too many variables" \
+		      "variables" \
+		      [format {o variablesReference [i %d] count [i 100]} \
+			   $dei_ref]] \
+	      0]
+set deivals [dict get $refs body variables]
+gdb_assert {[llength $deivals] == 2} "still just two members"
 
 set num [dict get $reg_scope variablesReference]
 lassign [dap_check_request_and_response "fetch all registers" \