Implement function call operations

This implement function call operations.

The current function call code relies on some very lengthy code
(evaluate_funcall is 398 lines...) to distinguish between the
different opcodes that might appear in the callee position.

Rather than try to replicate this, and have a function that tried to
dissect many different kinds of operation subclass, this patch instead
puts the work into the callee.  A new operation::evaluate_funcall
method is added, and then this is overridden in the classes that
require special treatment.

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

	* expression.h (class operation) <evaluate_funcall>: New methods.
	* expop.h (class scope_operation) <evaluate_funcall>: New method.
	(class var_value_operation) <evaluate_funcall>: New method.
	(class structop_base_operation) <evaluate_funcall>: New method.
	(class var_msym_value_operation) <evaluate_funcall>: New method.
	(class structop_member_base): New class.
	(class structop_member_operation): Derive from
	structop_member_base.
	(class structop_mptr_operation): Derive from
	structop_member_base.
	(class funcall_operation): New class.
	* eval.c (operation::evaluate_funcall)
	(var_value_operation::evaluate_funcall)
	(scope_operation::evaluate_funcall)
	(structop_member_base::evaluate_funcall)
	(structop_base_operation::evaluate_funcall): New methods.

1 files changed, 20 insertions, 0 deletions

diff --git a/gdb/expression.h b/gdb/expression.h
index 4d75058..d20857b 100644
--- a/gdb/expression.h
+++ b/gdb/expression.h
@@ -144,6 +144,19 @@ public:
   virtual value *evaluate_for_address (struct expression *exp,
 				       enum noside noside);
 
+  /* Evaluate a function call, with this object as the callee.
+     EXPECT_TYPE, EXP, and NOSIDE have the same meaning as in
+     'evaluate'.  ARGS holds the operations that should be evaluated
+     to get the arguments to the call.  */
+  virtual value *evaluate_funcall (struct type *expect_type,
+				   struct expression *exp,
+				   enum noside noside,
+				   const std::vector<operation_up> &args)
+  {
+    /* Defer to the helper overload.  */
+    return evaluate_funcall (expect_type, exp, noside, nullptr, args);
+  }
+
   /* True if this is a constant expression.  */
   virtual bool constant_p () const
   { return false; }
@@ -171,6 +184,13 @@ public:
 
 protected:
 
+  /* A helper overload that wraps evaluate_subexp_do_call.  */
+  value *evaluate_funcall (struct type *expect_type,
+			   struct expression *exp,
+			   enum noside noside,
+			   const char *function_name,
+			   const std::vector<operation_up> &args);
+
   /* Called by generate_ax to do the work for this particular
      operation.  */
   virtual void do_generate_ax (struct expression *exp,