我想捕获由库代码生成的异常并将它们包装在boost::optional
s (或std::experimental::optional
)中。我的代码适用于琐碎的情况,但在调用重载函数时很难推断出正确的类型。我已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;
}
尝试编译“损坏”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。有没有解决我的问题的方法,还是我被丑陋的函数指针黑客所困扰?
干杯,瑞恩