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

[Weimin Pan <weimin.pan@oracle.com>]

Don't call language_pass_by_reference() with function that has no return type.

Only call language_pass_by_reference(), which returns whether or not an 
additional initial argument has been given, when return_type is not NULL
in function aarch64_push_dummy_call().

Tested on aarch64-linux-gnu. No regressions.
---
 gdb/ChangeLog      | 6 ++++++
 gdb/aarch64-tdep.c | 4 +++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 6f4153b..4c5691f 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2018-05-23  Weimin Pan  <weimin.pan@oracle.com>
+
+	PR gdb/22736:
+	* aarch64-tdep.c (aarch64_push_dummy_call): Do not call
+	language_pass_by_reference if return_type is NULL.
+
 2018-05-14  Weimin Pan  <weimin.pan@oracle.com>
 
 	* minsyms.h (lookup_minimal_symbol_and_objfile): Remove declaration.
diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index 01566b4..b4633ff 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -1426,7 +1426,9 @@ 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);
+  lang_struct_return = (return_type != NULL
+			 ? language_pass_by_reference (return_type) 
+			 : 0);
 
   /* Set the return address.  For the AArch64, the return breakpoint
      is always at BP_ADDR.  */
-- 
1.8.3.1