stdruntimeerrorFile

std::runtime_error is a standard exception class in C++ that is part of the Standard Library. It is defined in the <stdexcept> header file. This class is used to report errors that can only be detected during runtime. It inherits from the std::exception class, which makes it part of the exception hierarchy in C++.

The std::runtime_error class is typically used to indicate errors that are not related to the logic of the program but rather to the environment in which the program is running. For example, it can be used to report errors such as failure to open a file, network errors, or other runtime conditions that are beyond the control of the program.

When an std::runtime_error exception is thrown, it can carry a descriptive error message. This message can be accessed using the what() member function, which returns a C-style string (const char*) describing the error.

Here is an example of how std::runtime_error can be used in a C++ program:

#include <iostream>

#include <stdexcept>

void openFile(const std::string& filename) {

// Simulate file opening failure

throw std::runtime_error("Failed to open file: " + filename);

}

int main() {

try {

openFile("example.txt");

} catch (const std::runtime_error& e) {

std::cerr << "Runtime error: " << e.what() << '\n';

}

return 0;

}

In this example, the openFile function simulates a failure to open a file and throws an std::runtime_error with a descriptive message. The main function catches this exception and prints the error message to the standard error stream.