Do not allow DAP clients to dereference "void *"

While investigating a different bug, I noticed that the DAP code would
report a "void *"-typed register as having children -- however,
requesting the children of this register would fail.

The issue here is that a plain "void *" can't be dereferenced.  This
patch changes the default visualizer to treat a "void *" as a scalar.

This adds a new test; but also arranges to examine all the returned
registers -- this was the first thing I attempted and it seemed
reasonable to have a test that double-checks that all the registers
really can be dereferenced as appropriate.

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

1 files changed, 10 insertions, 4 deletions

diff --git a/gdb/python/lib/gdb/printing.py b/gdb/python/lib/gdb/printing.py
index cba27d2..cda033f 100644
--- a/gdb/python/lib/gdb/printing.py
+++ b/gdb/python/lib/gdb/printing.py
@@ -415,11 +415,17 @@ def make_visualizer(value):
             result = NoOpArrayPrinter(ty, value)
         elif ty.code in (gdb.TYPE_CODE_STRUCT, gdb.TYPE_CODE_UNION):
             result = NoOpStructPrinter(ty, value)
-        elif ty.code in (
-            gdb.TYPE_CODE_PTR,
-            gdb.TYPE_CODE_REF,
-            gdb.TYPE_CODE_RVALUE_REF,
+        elif (
+            ty.code
+            in (
+                gdb.TYPE_CODE_PTR,
+                gdb.TYPE_CODE_REF,
+                gdb.TYPE_CODE_RVALUE_REF,
+            )
+            and ty.target().code != gdb.TYPE_CODE_VOID
         ):
+            # Note we avoid "void *" here because those pointers can't
+            # be dereferenced without a cast.
             result = NoOpPointerReferencePrinter(value)
         else:
             result = NoOpScalarPrinter(value)