使用boost::optional捕获和包装异常

我想捕获库代码生成的异常，并将它们包装在boost::optional s(或std::experimental::optional)中。我的代码可以处理一些琐碎的情况，但是在调用重载函数时很难推断出正确的类型。我将我的测试用例简化为:

// Compile with: clang++ -std=c++14 -stdlib=libc++ -Wall -Wshadow -Wextra -o except_to_optional except_to_optional.cpp
#include <iostream>
#include <boost/optional.hpp>
template<typename Func, typename... Args>
auto try_call(Func f, Args&&... args) noexcept -> boost::optional<std::decay_t<decltype(f(std::forward<Args>(args)...))>>
{
  using RT = std::decay_t<decltype(f(std::forward<Args>(args)...))>;
  try {
    return boost::make_optional<RT>(f(std::forward<Args>(args)...));
  } catch(...) {
    return boost::none;
  }
}
int func1(char * ptr)
{
  if (!ptr)
    throw 14;
  return strlen(ptr);
}
int func1(char * ptr, size_t len)
{
  if (!ptr)
    throw 14;
  const size_t calc_len = strlen(ptr);
  return calc_len < len ? calc_len : len;
}
int main(int argc, char **argv)
{
  char *omg = "omg";
#if 1
  // This is the desired syntax, but it fails
  auto val = try_call(func1, omg);
#else
  // This works, but its ugly
  int (*f)(char *) = func1;
  auto val = try_call(f, omg);
#endif
  if (val)
    std::cout << omg << " has a length of " << *val << "n";
  else
    std::cout << "Something went wrong...n";
  return 0;
}

当尝试编译"broken"示例时，我得到以下输出:

except_to_optional.cpp:50:14: error: no matching function for call to 'try_call'
  auto val = try_call(func1, omg);
             ^~~~~~~~
except_to_optional.cpp:17:6: note: candidate template ignored: couldn't infer template argument 'Func'
auto try_call(Func f, Args&&... args) noexcept -> boost::optional<std::decay_t<decltype(f(std::forward<Args>(args)...))>>
     ^

我可以通过创建具有正确类型的函数指针来回避这个问题，但这并不理想。是否有一个解决方案，我的问题，或者我坚持与丑陋的函数指针hack?

欢呼,瑞安