Re: [PATCH] KFAIL variable-length array tests which fail with Clang

[Tom de Vries <tdevries@suse.de>]

On 11/18/20 5:14 PM, Tom Tromey wrote:
>>>>>> "Gary" == Gary Benson via Gdb-patches <gdb-patches@sourceware.org> writes:
> 
> Gary> Clang describes the upper bounds of variable length arrays using
> Gary> a DW_AT_count attribute which references the DIE of a synthetic
> Gary> variable whose value is specified using a DW_AT_location.  In
> Gary> some cases GDB correctly handles these, but in other cases GDB
> Gary> adds an extra dereference causing the test to fail.  This commit
> Gary> marks these failing tests as caused by PR gdb/26905 when the
> Gary> test executable was built using Clang.
> 
> Shouldn't we just fix the gdb bug instead?

This adhoc patch:
...
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 3c598262913..d27e8613d1c 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -18644,7 +18644,9 @@ attr_to_dynamic_prop (const struct attribute
*attr, struct die
_info *die,
                struct dwarf_block *block = target_attr->as_block ();
                baton->locexpr.size = block->size;
                baton->locexpr.data = block->data;
-               baton->locexpr.is_reference = true;
+               gdb_byte last = block->data[block->size - 1];
+               baton->locexpr.is_reference
+                 = !(last == DW_OP_stack_value || last ==
DW_OP_implicit_value);
                prop->set_locexpr (baton);
                gdb_assert (prop->baton () != NULL);
              }
...
fixes gdb.base/vla-optimized-out.exp with clang-10 for me.

Thanks,
- Tom

> Or is there something preventing that?  I feel like I may not fully
> appreciate the problem.
> 
> Tom
>