[PATCH PR gdb/22736] [aarch64] gdb crashes on a conditional breakpoint with cast return type

[Alan Hayward <Alan.Hayward@arm.com>]

On aarch64, the (int) casting in the following causes a gdb segfault:
$ ./gdb ./gdb
(gdb) b dwarf2_physname if (int)strcmp (name, "another_thread_local") == 0
(gdb) run a.out         // use any a.out

This is due to getting a null pointer from TYPE_TARGET_TYPE, and then
using it for language_pass_by_reference().

Fixed by adding a null check, similar to other occurrences in gdb.

Tested on aarch64 with make check using unix, native_gdbserver.

Alan.


2018-03-01  Alan Hayward  <alan.hayward@arm.com>

	* aarch64-tdep.c (aarch64_push_dummy_call): Check for null
	return_type.

diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index f08945ea07101e1cd7906ca640c023ac7d189dd9..ef982c78fe64ceef3c7c378fd22d76604bf81c31 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -1382,7 +1382,7 @@ aarch64_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
   struct aarch64_call_info info;
   struct type *func_type;
   struct type *return_type;
-  int lang_struct_return;
+  int lang_struct_return = 0;

   memset (&info, 0, sizeof (info));

@@ -1424,7 +1424,8 @@ aarch64_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
      given an additional initial argument, a hidden pointer to the
      return slot in memory.  */
   return_type = TYPE_TARGET_TYPE (func_type);
-  lang_struct_return = language_pass_by_reference (return_type);
+  if (return_type != nullptr)
+    lang_struct_return = language_pass_by_reference (return_type);

   /* Set the return address.  For the AArch64, the return breakpoint
      is always at BP_ADDR.  */