On Fri, Feb 25, 2011 at 3:06 PM, Vicente Botet <vicente.botet@wanadoo.fr> wrote:
Lorenzo Caminiti wrote:
On Mon, Feb 7, 2011 at 5:29 PM, Steven Watanabe <watanabesj@gmail.com> wrote:
Hello all,
Why the following TYPEOF code does not compile on GCC but it does on MSVC? Is this a GCC bug? If so, is there a workaround for it?
#include <boost/typeof/typeof.hpp>
int f() { return -1; }
template<typename T> void g(T x) { int (deduce_func)(); typedef BOOST_TYPEOF_TPL(deduce_func) func_type; // error also if TYPEOF is used instead of TYPEOF_TPL
struct s { void call(func_type func) { func(); } // line 12 } ss; ss.call(f); // line 14 }
int main() { g(1); // line 18 return 0; }
$ g++ -Wall -Werror -I../../.. r03.cpp r03.cpp: In member function ‘void g(T)::s::call(__typeof__ (boost::type_of::ensure_obj(deduce_func))) [with T = int]’: r03.cpp:14: instantiated from ‘void g(T) [with T = int]’ r03.cpp:18: instantiated from here r03.cpp:12: error: ‘deduce_func’ was not declared in this scope
What is this error? I don't understand it because with the local struct at line 12 I am just accessing the type generated by the typedef and not the actual expression that was used to deduce such a type...
If I understand deduce_func should be a pointer to a function returning int. The declaration int (deduce_func)();
seems suspect to me. Have you tried with int (*deduce_func)();
Yes, using the *deduce_func fixed the issue. However, while this small example compiled by using *deduce_func, using *deduce_func caused an internal GCC internal in my lager Boost.Local code where I using this type deduction. I got around the GCC internal error doing the tagging and wrapping that Boost.ScopeExit does. Essentially, I ended up using code like this where boost_se_... are symbols defined by the scope exit macro expansion: #include <boost/type_traits.hpp> #include <boost/typeof/typeof.hpp> #include <boost/scope_exit.hpp> #include <iostream> int f() { return -1; } template<typename T> void g(T x) { T (*deduce_func)(); typedef BOOST_TYPEOF_TPL(*deduce_func) func_type; BOOST_SCOPE_EXIT_TPL( (deduce_func) ) { std::cout << "exiting" << std::endl; } BOOST_SCOPE_EXIT_END typedef typename boost::remove_pointer<typename boost_se_params_t_14::boost_se_param_t_0_14>::type ftype; typedef typename boost::function_traits<ftype>::result_type rtype; struct s { rtype call(typename boost_se_params_t_14::boost_se_param_t_0_14 func) { func(); return -1; } } ss; ss.call(&f); } int main() { g(1); return 0; } My Boost.Local code using code similar to the above now works on both GCC and MSVC (without any internal compiler error). Thanks. -- Lorenzo