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Defined in header <exception> | ||
template<class T> [[noreturn]]void throw_with_nested( T&& t); | (since C++11) (constexpr since C++26) | |
Ifstd::decay<T>::type is a non-final non-union class type that is neitherstd::nested_exception nor derived fromstd::nested_exception, throws an exception of an unspecified type that is publicly derived from bothstd::nested_exception and fromstd::decay<T>::type, and constructed fromstd::forward<T>(t). The default constructor of thenested_exception base class callsstd::current_exception, capturing the currently handled exception object, if any, in astd::exception_ptr.
Otherwise, throwsstd::forward<T>(t).
Requires thatstd::decay<T>::type isCopyConstructible.
Contents |
| t | - | the exception object to throw |
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_constexpr_exceptions | 202411L | (C++26) | constexpr for exception types |
Demonstrates construction and recursion through a nested exception object.
#include <exception>#include <fstream>#include <iostream>#include <stdexcept>#include <string> // prints the explanatory string of an exception. If the exception is nested,// recurses to print the explanatory string of the exception it holdsvoid print_exception(conststd::exception& e,int level=0){std::cerr<<std::string(level,' ')<<"exception: "<< e.what()<<'\n';try{std::rethrow_if_nested(e);}catch(conststd::exception& nestedException){ print_exception(nestedException, level+1);}catch(...){}} // sample function that catches an exception and wraps it in a nested exceptionvoid open_file(conststd::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 exceptionvoid 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 exceptionint main(){try{ run();}catch(conststd::exception& e){ print_exception(e);}}
Possible output:
exception: run() failed exception: Couldn't open nonexistent.file exception: basic_ios::clear
(C++11) | a mixin type to capture and store current exceptions (class)[edit] |
(C++11) | throws the exception from astd::nested_exception (function template)[edit] |
