Change enable_thread_stack_temporaries to an RAII class

This started as a patch to change enable_thread_stack_temporaries to
be an RAII class, but then I noticed that this code used a VEC, so I
went ahead and did a bit more C++-ification, changing
stack_temporaries_enabled to a bool and changing stack_temporaries to
a std::vector.

Regression tested by the buildbot.

gdb/ChangeLog
2018-03-08  Tom Tromey  <tom@tromey.com>

	* infcall.c (struct call_return_meta_info)
	<stack_temporaries_enabled>: Remove.
	(get_call_return_value, call_function_by_hand_dummy): Update.
	* thread.c (disable_thread_stack_temporaries): Remove.
	(enable_thread_stack_temporaries): Remove.
	(thread_stack_temporaries_enabled_p): Return bool.
	(push_thread_stack_temporary, value_in_thread_stack_temporaries)
	(get_last_thread_stack_temporary): Update.
	* eval.c (evaluate_subexp): Update.
	* gdbthread.h (class enable_thread_stack_temporaries): Now a
	class, not a function.
	(value_ptr, value_vec): Remove typedefs.
	(class thread_info) <stack_temporaries_enabled>: Now bool.
	<stack_temporaries>: Now a std::vector.
	(thread_stack_temporaries_enabled_p)
	(value_in_thread_stack_temporaries): Return bool.

1 files changed, 5 insertions, 12 deletions

diff --git a/gdb/eval.c b/gdb/eval.c
index 4899011..b2032c3 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -69,27 +69,20 @@ struct value *
 evaluate_subexp (struct type *expect_type, struct expression *exp,
 		 int *pos, enum noside noside)
 {
-  struct cleanup *cleanups;
   struct value *retval;
-  int cleanup_temps = 0;
 
+  gdb::optional<enable_thread_stack_temporaries> stack_temporaries;
   if (*pos == 0 && target_has_execution
       && exp->language_defn->la_language == language_cplus
       && !thread_stack_temporaries_enabled_p (inferior_ptid))
-    {
-      cleanups = enable_thread_stack_temporaries (inferior_ptid);
-      cleanup_temps = 1;
-    }
+    stack_temporaries.emplace (inferior_ptid);
 
   retval = (*exp->language_defn->la_exp_desc->evaluate_exp)
     (expect_type, exp, pos, noside);
 
-  if (cleanup_temps)
-    {
-      if (value_in_thread_stack_temporaries (retval, inferior_ptid))
-	retval = value_non_lval (retval);
-      do_cleanups (cleanups);
-    }
+  if (stack_temporaries.has_value ()
+      && value_in_thread_stack_temporaries (retval, inferior_ptid))
+    retval = value_non_lval (retval);
 
   return retval;
 }