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std::throw_with_nested - cppreference.com

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<metanoindex/>

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Elemento definito nell'header

<exception>

template< class T > [[noreturn]] void throw_with_nested( T&& t );

 (dal C++11)

Genera un'eccezione di tipo non specificato, che deriva sia da std::nested_exception e da std::remove_reference<T>::type, e costruito da std::forward<T>(t). Il costruttore di default del genitore nested_exception chiama std::current_exception, catturando l'oggetto eccezione attualmente gestita, se del caso, in std::exception_ptr.

Original:

Throws an exception of unspecified type that is derived from both std::nested_exception and from std::remove_reference<T>::type, and constructed from std::forward<T>(t). The default constructor of the nested_exception parent calls std::current_exception, capturing the currently handled exception object, if any, in std::exception_ptr.

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Se std::remove_reference<T>::type è già derivato da std::nested_exception, lancia semplicemente std::forward<T>(t).

Original:

If std::remove_reference<T>::type is already derived from std::nested_exception, simply throws std::forward<T>(t).

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Richiede che std::remove_reference<T>::type è CopyConstructible

Original:

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Parametri

t -

l'oggetto di un'eccezione da generare

Original:

the exception object to throw

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Valore di ritorno

(Nessuno)

Original:

(none)

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Esempio

[edit]

Dimostra costruzione e ricorsione attraverso un oggetto eccezione nidificata

Original:

Demonstrates construction and recursion through a nested exception object

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#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

Vedi anche

un tipo mixin per acquisire e memorizzare le eccezioni attuali

Original:

a mixin type to capture and store current exceptions

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(classe) [modifica]

genera l'eccezione di un std::nested_exception

Original:

throws the exception from a std::nested_exception

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(funzione di modello) [modifica]