Emit DAPException when too many variable children are reqeusted

PR dap/33228 points out a failure that occurs when the DAP client
requests more children of a variable than actually exist.  Currently,
gdb throws a somewhat confusing exception.  This patch changes this
code to throw a DAPException instead, resulting in a more ordinary and
readable failure.

The spec seems to be silent on what to do in this case.  I chose an
exception on the theory that it's easier to be strict now and lift the
restriction later (if needed) than vice versa.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=33228

1 files changed, 4 insertions, 0 deletions

diff --git a/gdb/python/lib/gdb/dap/varref.py b/gdb/python/lib/gdb/dap/varref.py
index 8a13c51..1b54fe7 100644
--- a/gdb/python/lib/gdb/dap/varref.py
+++ b/gdb/python/lib/gdb/dap/varref.py
@@ -146,6 +146,10 @@ class BaseReference(ABC):
         if self._children is None:
             self._children = [None] * self.child_count()
         for idx in range(start, start + count):
+            if idx >= len(self._children):
+                raise DAPException(
+                    f"requested child {idx} outside range of variable {self._ref}"
+                )
             if self._children[idx] is None:
                 (name, value) = self.fetch_one_child(idx)
                 name = self._compute_name(name)