Defined in header <exception> | ||
---|---|---|
template< class T > [[noreturn]] void throw_with_nested( T&& t ); | (since C++11) |
If std::remove_reference_t<T>
is a non-final non-union class type that is neither std::nested_exception
nor derived from std::nested_exception
, throws an exception of an unspecified type that is publicly derived from both std::nested_exception
and from std::remove_reference_t<T>
, and constructed from std::forward<T>(t)
. The default constructor of the nested_exception
base class calls std::current_exception
, capturing the currently handled exception object, if any, in a std::exception_ptr
.
Otherwise, throws std::forward<T>(t)
.
Requires that std::remove_reference<T>::type
is CopyConstructible
.
Parameters
t | - | the exception object to throw |
Return value
(none).
Example
Demonstrates construction and recursion through a nested exception object.
#include <iostream> #include <stdexcept> #include <exception> #include <string> #include <fstream> // prints the explanatory string of an exception. If the exception is nested, // recurses to print the explanatory of the exception it holds void print_exception(const std::exception& e, int level = 0) { std::cerr << std::string(level, ' ') << "exception: " << e.what() << '\n'; try { std::rethrow_if_nested(e); } catch(const std::exception& e) { print_exception(e, level+1); } catch(...) {} } // sample function that catches an exception and wraps it in a nested exception void open_file(const std::string& s) { try { std::ifstream file(s); file.exceptions(std::ios_base::failbit); } catch(...) { std::throw_with_nested( std::runtime_error("Couldn't open " + s) ); } } // sample function that catches an exception and wraps it in a nested exception void run() { try { open_file("nonexistent.file"); } catch(...) { std::throw_with_nested( std::runtime_error("run() failed") ); } } // runs the sample function above and prints the caught exception int main() { try { run(); } catch(const std::exception& e) { print_exception(e); } }
Output:
exception: run() failed exception: Couldn't open nonexistent.file exception: basic_ios::clear
See also
(C++11) | a mixin type to capture and store current exceptions (class) |
(C++11) | throws the exception from a std::nested_exception (function template) |
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