bad_error_eg.cpp:

- Example of error messages with and without compiler help


[SVN r13251]

include/boost/function.hpp

@@ -454,16 +454,37 @@ namespace boost {
     typedef function self_type;                                     
                                                                             
     function() : base_type() {}                                     
-                                                                            
+                                                             
+#ifdef BOOST_COMPILER_HOOKS               
     template<typename Functor>                                              
-    function(Functor BOOST_FUNCTION_TARGET_FIX(const &) f) : base_type(f) {}
+    function(Functor BOOST_FUNCTION_TARGET_FIX(const &) f) : 
+      base_type(f, mixin_type(), detail::function::int_value<1>()) 
+    {
+    }
+
+  private:
+    template<typename Functor, int N>
+    function(Functor BOOST_FUNCTION_TARGET_FIX(const &) f, 
+             detail::function::int_value<N>) : 
+      base_type(f, mixin_type(), detail::function::int_value<N+1>())
+    {
+    }
+  public:
+#else
+    template<typename Functor>                                              
+    function(Functor BOOST_FUNCTION_TARGET_FIX(const &) f) : base_type(f) {}   
+#endif // !BOOST_COMPILER_HOOKS
                       
     function(const self_type& f) : base_type(static_cast<const base_type&>(f)){}
          
     template<typename Functor>
     self_type& operator=(Functor BOOST_FUNCTION_TARGET_FIX(const &) f)
     {
+#ifdef BOOST_COMPILER_HOOKS
+      self_type(f, detail::function::int_value<1>()).swap(*this);
+#else
       self_type(f).swap(*this);
+#endif // !BOOST_COMPILER_HOOKS
       return *this;
     }
 

include/boost/function/errors.hpp

@@ -0,0 +1,247 @@
+// Boost.Function library
+
+// Copyright (C) 2001 Doug Gregor (gregod@cs.rpi.edu)
+//
+// Permission to copy, use, sell and distribute this software is granted
+// provided this copyright notice appears in all copies.
+// Permission to modify the code and to distribute modified code is granted
+// provided this copyright notice appears in all copies, and a notice
+// that the code was modified is included with the copyright notice.
+//
+// This software is provided "as is" without express or implied warranty,
+// and with no claim as to its suitability for any purpose.
+ 
+// For more information, see http://www.boost.org
+// Note: this header is a header template and must NOT have multiple-inclusion
+// protection. 
+
+#ifdef BOOST_COMPILER_HOOKS
+
+#ifndef BOOST_FUNCTION_ERRORS_HPP
+#  include <boost/config.hpp>
+#  include <boost/preprocessor/enum_params.hpp>
+#  include <boost/preprocessor/stringize.hpp>
+#  include <ext/compiler>
+#endif // BOOST_FUNCTION_ERRORS_HPP
+
+#define BOOST_F_BAD_ARGS \
+  BOOST_PP_CAT(incompatible_args_msg,BOOST_FUNCTION_NUM_ARGS)
+
+#define BOOST_F_CHECK_ARGS \
+  BOOST_PP_CAT(check_args,BOOST_FUNCTION_NUM_ARGS)
+
+#define BOOST_F_BAD_RETURN \
+  BOOST_PP_CAT(incompatible_return_msg,BOOST_FUNCTION_NUM_ARGS)
+
+#define BOOST_F_CHECK_RETURN \
+  BOOST_PP_CAT(check_return,BOOST_FUNCTION_NUM_ARGS)
+
+#define BOOST_F_CHECK_TARGET \
+  BOOST_PP_CAT(check_target,BOOST_FUNCTION_NUM_ARGS)
+
+// Comma if nonzero number of arguments
+#define BOOST_F_COMMA BOOST_PP_COMMA_IF(BOOST_FUNCTION_NUM_ARGS)
+
+#define BOOST_F_TYPE_PLACEHOLDER(I,P) \
+  BOOST_PP_IF(I, ", ",) BOOST_PP_STRINGIZE(%t)
+
+#define BOOST_F_ARG_TYPE(I,P) \
+  BOOST_PP_COMMA_IF(I) arg< type<T##I> 
+
+#define BOOST_F_CLOSE_TMPL(I, P) >
+
+namespace boost {
+  namespace detail {
+    namespace function {
+#ifndef BOOST_FUNCTION_ERRORS_HPP
+      template<bool> struct truth {};
+      template<int> struct int_value {};
+
+      using __gnu_cxx::arg;
+      using __gnu_cxx::type;
+      using __gnu_cxx::can_instantiate;
+      using __gnu_cxx::error;
+
+      template<typename T, void (T::*p)()>
+      struct pmf {};
+
+      template<typename Constraint>
+      struct constraint {
+        typedef pmf<Constraint, &Constraint::constraints> force;
+      };
+
+      template<bool, typename Error> struct maybe_emit_error;
+      template<typename Error> struct maybe_emit_error<true, Error> {};
+
+      template<typename Error> 
+      struct maybe_emit_error<false, Error> {
+        BOOST_STATIC_CONSTANT(int, junk = sizeof(Error));
+      };
+      
+      // Check the given constraint. If it is not satisfied, emit an error
+      // message suppressing N instantiation levels (not including the levels
+      // deeper than this instantiation).
+      template<typename Constraint, int N = 0>
+      struct check_constraint
+      {
+        // True if the constraint is met
+        BOOST_STATIC_CONSTANT(bool, 
+                              value = can_instantiate<constraint<Constraint> >
+                                        ::value);
+      private:
+        // Possibly emit an error message
+        typedef typename Constraint::msg error_msg;
+        typedef typename error_msg::args error_msg_args;
+        typedef error<error_msg, error_msg_args, N+2> actual_error;
+        typedef maybe_emit_error<value, actual_error> possible_error;
+        BOOST_STATIC_CONSTANT(int, junk = sizeof(possible_error));
+      };
+
+      // Help suppress redundant error messages
+      template<bool, typename Check> struct maybe_check;
+
+      template<typename Check>
+      struct maybe_check<false, Check>
+      {
+        BOOST_STATIC_CONSTANT(bool, value = false);
+      };
+
+      template<typename Check>
+      struct maybe_check<true, Check>
+      {
+        BOOST_STATIC_CONSTANT(bool, value = Check::value);
+      };
+
+#endif // !BOOST_FUNCTION_ERRORS_HPP
+
+      // Error message when the arguments are not compatible
+      template<typename F BOOST_F_COMMA BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,typename T)>
+      struct BOOST_F_BAD_ARGS {
+        // Construct the argument list
+        typedef arg<type<F> BOOST_F_COMMA BOOST_PP_REPEAT(BOOST_FUNCTION_NUM_ARGS, BOOST_F_ARG_TYPE, x) BOOST_PP_REPEAT(BOOST_FUNCTION_NUM_ARGS, BOOST_F_CLOSE_TMPL, x) > args;
+
+        // The error message text
+        static const char* text;
+      };
+
+#if BOOST_FUNCTION_NUM_ARGS == 0
+      template<typename F>
+      const char* BOOST_F_BAD_ARGS<F>::text 
+        = "objects of type '%t' cannot be invoked with no arguments";
+#else
+      // Construct the error message when arguments are not compatible
+      template<typename F BOOST_F_COMMA BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,typename T)>
+      const char* BOOST_F_BAD_ARGS<
+                    F BOOST_F_COMMA
+                    BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,T)>
+        ::text = "objects of type '%t' cannot be invoked with Boost.Function "
+                 "argument types '("
+                 BOOST_PP_REPEAT(BOOST_FUNCTION_NUM_ARGS,
+                                 BOOST_F_TYPE_PLACEHOLDER,x)
+                 ")'";
+#endif // BOOST_FUNCTION_NUM_ARGS != 0
+
+      // Concept check to determine if argument types are compatible
+      template<typename F BOOST_F_COMMA
+               BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,typename T)>
+      struct BOOST_F_CHECK_ARGS {
+        typedef BOOST_F_BAD_ARGS<F BOOST_F_COMMA BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,T)> msg;
+
+        F f;
+#define BOOST_F_ARG(I,P) T##I a##I;
+        BOOST_PP_REPEAT(BOOST_FUNCTION_NUM_ARGS,BOOST_F_ARG,)
+#undef BOOST_F_ARG
+
+        void constraints() 
+        {
+          f(BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,a));
+        }
+      };
+
+      // Error message when the return types are compatible
+      template<typename F, typename R BOOST_F_COMMA
+               BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,typename T)>
+      struct BOOST_F_BAD_RETURN {
+        // Arguments to format the error message
+        typedef arg<type<F> BOOST_F_COMMA BOOST_PP_REPEAT(BOOST_FUNCTION_NUM_ARGS, BOOST_F_ARG_TYPE, x) , arg<type<R> > BOOST_PP_REPEAT(BOOST_FUNCTION_NUM_ARGS, BOOST_F_CLOSE_TMPL, x) > args;
+
+        // Error message text
+        static const char* text;
+      };
+
+#if BOOST_FUNCTION_NUM_ARGS == 0
+      template<typename F, typename R>
+      const char* BOOST_F_BAD_RETURN<F, R>::text = 
+        "return type when invoking object of type '%t' with no arguments is "
+        "not convertible to Boost.Function declared return type '%t'";
+#else
+      // Construct the error message when return types are not compatible
+      template<typename F, typename R BOOST_F_COMMA
+               BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,typename T)>
+      const char* BOOST_F_BAD_RETURN<
+                    F, R BOOST_F_COMMA
+                    BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,T)>
+        ::text = "return type when invoking object of type '%t' with argument"
+                 " types '("
+                 BOOST_PP_REPEAT(BOOST_FUNCTION_NUM_ARGS,
+                                 BOOST_F_TYPE_PLACEHOLDER,x)
+                 ")' is not convertible to Boost.Function declared return "
+                 "type '%t'";
+#endif // BOOST_FUNCTION_NUM_ARGS != 0
+
+      // Concept check to determine if return types are compatible
+      template<typename F, typename R BOOST_F_COMMA
+               BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,typename T)>
+      struct BOOST_F_CHECK_RETURN {
+        typedef BOOST_F_BAD_RETURN<
+                  F, R BOOST_F_COMMA
+                  BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,T)> msg;
+
+        F f;
+#define BOOST_F_ARG(I,P) T##I a##I;
+        BOOST_PP_REPEAT(BOOST_FUNCTION_NUM_ARGS,BOOST_F_ARG,)
+#undef BOOST_F_ARG
+
+        R foo()
+        {
+          return f(BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,a));
+        }
+
+        void constraints()
+        {
+          R (BOOST_F_CHECK_RETURN::*p)() = &BOOST_F_CHECK_RETURN::foo;
+        }
+      };
+
+      template<typename F, typename R BOOST_F_COMMA
+               BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,typename T), 
+               int N=0>
+      struct BOOST_F_CHECK_TARGET {
+        typedef check_constraint<BOOST_F_CHECK_ARGS<F BOOST_F_COMMA BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,T)>,N+1> check_args;
+        typedef check_constraint<BOOST_F_CHECK_RETURN<F, R BOOST_F_COMMA BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,T)>,N+2> check_return;
+
+        BOOST_STATIC_CONSTANT(bool, args_ok = check_args::value);
+        BOOST_STATIC_CONSTANT(bool, 
+                              value = 
+                                (maybe_check<args_ok, check_return>::value));
+      };
+    } // end namespace function
+  } // end namespace function
+} // end namespace function
+
+#undef BOOST_F_COMMA
+#undef BOOST_F_BAD_ARGS
+#undef BOOST_F_CHECK_ARGS
+#undef BOOST_F_BAD_RETURN
+#undef BOOST_F_CHECK_RETURN
+#undef BOOST_F_CHECK_TARGET
+#undef BOOST_F_TYPE_PLACEHOLDER
+#undef BOOST_F_ARG_TYPE
+#undef BOOST_F_CLOSE_TMPL
+
+#endif // BOOST_COMPILER_HOOKS
+
+// Don't redo work done in the first inclusion
+#ifndef BOOST_FUNCTION_ERRORS_HPP
+#  define BOOST_FUNCTION_ERRORS_HPP
+#endif // BOOST_FUNCTION_ERRORS_HPP

include/boost/function/function_template.hpp

@@ -25,6 +25,9 @@
 #  include <boost/mem_fn.hpp>
 #endif // BOOST_FUNCTION_FUNCTION_TEMPLATE_HPP
 
+// Include better error handling for 
+#include <boost/function/errors.hpp>
+
 // Type of the default allocator
 #ifndef BOOST_NO_STD_ALLOCATOR
 #  define BOOST_FUNCTION_DEFAULT_ALLOCATOR std::allocator<function_base>
@@ -288,6 +291,16 @@ namespace boost {
       this->assign_to_own(f);
     }
 
+#ifdef BOOST_COMPILER_HOOKS
+    template<typename Functor, int N>
+    BOOST_FUNCTION_FUNCTION(Functor f, const Mixin& m, 
+                            detail::function::int_value<N> iv) :
+      function_base(), Mixin(m), invoker(0)
+    {
+      this->assign_to(f, iv);
+    }
+#endif // BOOST_COMPILER_HOOKS
+
     ~BOOST_FUNCTION_FUNCTION() { clear(); }
 
     result_type operator()(BOOST_FUNCTION_PARMS) const
@@ -318,14 +331,25 @@ namespace boost {
     BOOST_FUNCTION_FUNCTION& 
     operator=(Functor BOOST_FUNCTION_TARGET_FIX(const &) f)
     {
+#ifdef BOOST_COMPILER_HOOKS
+      self_type(f, static_cast<const Mixin&>(*this),
+                detail::function::int_value<1>()).swap(*this);
+#else
       self_type(f, static_cast<const Mixin&>(*this)).swap(*this);
+#endif // !BOOST_COMPILER_HOOKS
+
       return *this;
     }
 
     template<typename Functor>
     void set(Functor BOOST_FUNCTION_TARGET_FIX(const &) f)
     {
+#ifdef BOOST_COMPILER_HOOKS
+      self_type(f, static_cast<const Mixin&>(*this),
+                detail::function::int_value<1>()).swap(*this);
+#else
       self_type(f, static_cast<const Mixin&>(*this)).swap(*this);
+#endif // !BOOST_COMPILER_HOOKS
     }
 
     // Assignment from another BOOST_FUNCTION_FUNCTION
@@ -378,12 +402,48 @@ namespace boost {
       }          
     }
 
+#ifdef BOOST_COMPILER_HOOKS
+    template<typename Functor>
+    void assign_to(Functor f)
+    {
+      return assign_to(f, detail::function::int_value<1>());
+    }
+
+    template<typename Functor, int N>
+    void assign_to(Functor f, detail::function::int_value<N>)
+    {
+      typedef detail::function::BOOST_JOIN(check_target,BOOST_FUNCTION_NUM_ARGS)<
+                Functor, R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_ARGS,
+                N+2>
+        check_target;
+
+      enum { ok = check_target::value };
+
+      maybe_assign_to(f, detail::function::truth<ok>());
+    }
+
+    template<typename Functor>
+    void maybe_assign_to(Functor f, detail::function::truth<true>)
+    {
+      typedef typename detail::function::get_function_tag<Functor>::type tag;
+
+      this->assign_to(f, tag());
+    }
+
+    template<typename Functor>
+    void maybe_assign_to(Functor f, detail::function::truth<false>)
+    {
+      // Do nothing, to avoid even more error messages
+    }
+#else
     template<typename Functor>
     void assign_to(Functor f)
     {
       typedef typename detail::function::get_function_tag<Functor>::type tag;
+
       this->assign_to(f, tag());
     }
+#endif // !BOOST_COMPILER_HOOKS
 
     template<typename FunctionPtr>
     void assign_to(FunctionPtr f, detail::function::function_ptr_tag)

test/bad_error_eg.cpp

@@ -0,0 +1,36 @@
+// Boost.Function library
+
+// Copyright (C) 2001 Doug Gregor (gregod@cs.rpi.edu)
+//
+// Permission to copy, use, sell and distribute this software is granted
+// provided this copyright notice appears in all copies.
+// Permission to modify the code and to distribute modified code is granted
+// provided this copyright notice appears in all copies, and a notice
+// that the code was modified is included with the copyright notice.
+//
+// This software is provided "as is" without express or implied warranty,
+// and with no claim as to its suitability for any purpose.
+
+// For more information, see http://www.boost.org
+
+#define BOOST_INCLUDE_MAIN
+#include <boost/test/test_tools.hpp>
+#include <boost/function.hpp>
+
+using namespace boost;
+
+class X {};
+
+int foo(X*);
+X* bar(double);
+
+int test_main(int, char* [])
+{
+  function<int, float> f(&foo);
+  f = &bar;
+  
+
+  BOOST_CRITICAL_ERROR("This should not have compiled.");
+
+  return 0;
+}