Introduce ada_var_msym_value_operation

This adds class ada_var_msym_value_operation, which implements
OP_VAR_MSYM_VALUE for Ada.

gdb/ChangeLog
2021-03-08  Tom Tromey  <tom@tromey.com>

	* ada-lang.c (ada_var_msym_value_operation::evaluate_for_cast):
	New method.
	* ada-exp.h (class ada_var_msym_value_operation): New.

3 files changed, 48 insertions, 0 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index adf910f..34f80b4 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,11 @@
 2021-03-08  Tom Tromey  <tom@tromey.com>
 
+	* ada-lang.c (ada_var_msym_value_operation::evaluate_for_cast):
+	New method.
+	* ada-exp.h (class ada_var_msym_value_operation): New.
+
+2021-03-08  Tom Tromey  <tom@tromey.com>
+
 	* ada-lang.c (ada_var_value_operation::evaluate_for_cast)
 	(ada_var_value_operation::evaluate): New methods.
 	* ada-exp.h (class ada_var_value_operation): New.
diff --git a/gdb/ada-exp.h b/gdb/ada-exp.h
index 0f2f62f..0fe6ecf 100644
--- a/gdb/ada-exp.h
+++ b/gdb/ada-exp.h
@@ -304,6 +304,23 @@ protected:
   using operation::do_generate_ax;
 };
 
+/* Variant of var_msym_value_operation for Ada.  */
+class ada_var_msym_value_operation
+  : public var_msym_value_operation
+{
+public:
+
+  using var_msym_value_operation::var_msym_value_operation;
+
+  value *evaluate_for_cast (struct type *expect_type,
+			    struct expression *exp,
+			    enum noside noside) override;
+
+protected:
+
+  using operation::do_generate_ax;
+};
+
 } /* namespace expr */
 
 #endif /* ADA_EXP_H */
diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index ee8e8e1..eb21748 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -10554,6 +10554,31 @@ ada_unop_atr_operation::evaluate (struct type *expect_type,
 }
 
 value *
+ada_var_msym_value_operation::evaluate_for_cast (struct type *expect_type,
+						 struct expression *exp,
+						 enum noside noside)
+{
+  if (noside == EVAL_AVOID_SIDE_EFFECTS)
+    return value_zero (expect_type, not_lval);
+
+  value *val = evaluate_var_msym_value (noside,
+					std::get<1> (m_storage),
+					std::get<0> (m_storage));
+
+  val = ada_value_cast (expect_type, val);
+
+  /* Follow the Ada language semantics that do not allow taking
+     an address of the result of a cast (view conversion in Ada).  */
+  if (VALUE_LVAL (val) == lval_memory)
+    {
+      if (value_lazy (val))
+	value_fetch_lazy (val);
+      VALUE_LVAL (val) = not_lval;
+    }
+  return val;
+}
+
+value *
 ada_var_value_operation::evaluate_for_cast (struct type *expect_type,
 					    struct expression *exp,
 					    enum noside noside)