Fix debuginfo for unsized struct members

The member was given the size of a fat pointer, which caused
llvm to emit DWARF attributes for a 128-bit bitfield.

src/librustc_trans/debuginfo/metadata.rs

@@ -906,7 +906,7 @@ impl<'tcx> StructMemberDescriptionFactory<'tcx> {
 
             MemberDescription {
                 name: name,
-                llvm_type: type_of::type_of(cx, fty),
+                llvm_type: type_of::in_memory_type_of(cx, fty),
                 type_metadata: type_metadata(cx, fty, self.span),
                 offset: offset,
                 flags: DIFlags::FlagZero,

src/test/debuginfo/unsized.rs

@@ -0,0 +1,45 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-flags:-g
+
+// === GDB TESTS ===================================================================================
+
+// gdb-command:run
+
+// gdb-command:print *a
+// gdbg-check:$1 = {value = [...] "abc"}
+// gdbr-check:$1 = unsized::Foo<[u8]> {value: [...]}
+
+// gdb-command:print *b
+// gdbg-check:$2 = {value = {value = [...] "abc"}}
+// gdbr-check:$2 = unsized::Foo<unsized::Foo<[u8]>> {value: unsized::Foo<[u8]> {value: [...]}}
+
+
+#![feature(omit_gdb_pretty_printer_section)]
+#![omit_gdb_pretty_printer_section]
+
+struct Foo<T: ?Sized> {
+    value: T
+}
+
+fn main() {
+    let foo: Foo<Foo<[u8; 4]>> = Foo {
+        value: Foo {
+            value: *b"abc\0"
+        }
+    };
+    let a: &Foo<[u8]> = &foo.value;
+    let b: &Foo<Foo<[u8]>> = &foo;
+
+    zzz(); // #break
+}
+
+fn zzz() { () }