[PATCH 1/2] Fix BZ 25065 - Ensure that physnames are computed for inherited DIEs

[Kevin Buettner <kevinb@redhat.com>]

This is a fix for BZ 25065.

GDB segfaults when running either gdb.cp/subtypes.exp or
gdb.cp/local.exp in conjunction with using the -flto compiler/linker
flag.

A much simpler program, which was used to help create the test for
this fix, is:

-- doit.cc --
int main()
{
  class Foo {
  public:
    int doit ()
    {
      return 0;
    }
  };

  Foo foo;

  return foo.doit ();
}
-- end doit.cc --

gcc -o doit -flto -g doit.cc
gdb -q doit
Reading symbols from doit...
(gdb) ptype main::Foo
type = class Foo {
Segmentation fault (core dumped)

The segfault occurs due to a NULL physname in
c_type_print_base_struct_union in c-typeprint.c.  Specifically,
calling is_constructor_name() eventually causes the SIGSEGV is this
code in c-typeprint.c:

	      const char *physname = TYPE_FN_FIELD_PHYSNAME (f, j);
	      int is_full_physname_constructor =
		TYPE_FN_FIELD_CONSTRUCTOR (f, j)
		|| is_constructor_name (physname)
		|| is_destructor_name (physname)
		|| method_name[0] == '~';

However, looking at compute_delayed_physnames(), we see that
the TYPE_FN_FIELD_PHYSNAME field should never be NULL.  This
field will be set to "" for NULL physnames:

      physname = dwarf2_physname (mi.name, mi.die, cu);
      TYPE_FN_FIELD_PHYSNAME (fn_flp->fn_fields, mi.index)
	= physname ? physname : "";

For this particular case, it turns out that compute_delayed_physnames
wasn't being called, which left TYPE_FN_FIELD_PHYSNAME set to the NULL
value that it started with when that data structure was allocated.

The place to fix it, I think, is towards the end of
inherit_abstract_dies().  My fix causes the origin CU's method_list
(which is simply the list of methods whose physnames still
need to be computed) to be added to the CU which is doing the
inheriting.

Another way to fix it might be call compute_delayed_physnames() from
inherit_abstract_dies(), but I wasn't confident that all needed types
would be known at that point.  It seemed safer to defer the physname
computation until the inheriting CU is completely processed.

gdb/ChangeLog:

	* dwarf2read.c (inherit_abstract_dies): Ensure that delayed
	physnames are computed for inherited DIEs.
---
 gdb/dwarf2read.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index ee9df34ed2..f7ef122933 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -13666,6 +13666,17 @@ inherit_abstract_dies (struct die_info *die, struct dwarf2_cu *cu)
       origin_child_die = sibling_die (origin_child_die);
     }
   origin_cu->list_in_scope = origin_previous_list_in_scope;
+
+  if (cu != origin_cu && !origin_cu->method_list.empty ())
+    {
+      /* Add list of methods found in origin_cu to the list in cu.  These
+         methods still need to have their physnames computed in
+	 compute_delayed_physnames().  */
+      cu->method_list.insert (cu->method_list.end (),
+                              origin_cu->method_list.begin (),
+			      origin_cu->method_list.end ());
+      origin_cu->method_list.clear ();
+    }
 }
 
 static void
-- 
2.21.0