std::unexpected_handler(3)

💖 NAME 💖

std::unexpected_handler — std::unexpected_handler

Hii bestie 💅 welcome to the std::unexpected_handler(3) page from the C++ Standard Libary. Yes, that's the whole name up there — we're keeping it iconic and exact. 🎀

✨ Synopsis ✨

Defined in header <exception>

typedef void (*unexpected_handler)();  (deprecated in C++11)
                                       (removed in C++17)

Okay so quick vibe check: this type is deprecated in C++11 and removed in C++17, so if you meet it in the wild it's giving vintage-callback energy 👑

std::unexpected_handler is the function pointer type (pointer to function that takes no arguments and returns void), which is installed and queried by the functions std::set_unexpected and std::get_unexpected and called by std::unexpected.

The C++ implementation provides a default std::unexpected_handler function, which calls std::terminate(). If the null pointer value is installed (by means of std::set_unexpected), the implementation may restore the default handler instead. May, bestie — not "will" — read it again 😭

A user-defined std::unexpected_handler is expected to either terminate the program or throw an exception. If it throws an exception, one of the following three situations may be encountered:

1. The exception thrown by std::unexpected_handler satisfies the dynamic exception specification that was violated earlier. The new exception is allowed to escape the function and stack unwinding continues.
2. The exception thrown by std::unexpected_handler still violates the exception specification:
   • 2a) however, the exception specification allows std::bad_exception: the thrown exception object is destroyed, and std::bad_exception is constructed by the C++ runtime and thrown instead.
   • 2b) the exception specification does not allow std::bad_exception: std::terminate() is called.

🚨 No cap: those std::terminate() paths are real. If your handler lands in 2b, the program is done — periodt.

👀 See also 👀

• unexpected (removed in C++17) — function called when dynamic exception specification is violated (function)
• set_unexpected (removed in C++17) — changes the function to be called by std::unexpected (function)
• get_unexpected (C++11)(removed in C++17) — obtains the current unexpected_handler (function)

Source/version/date sign-off, bestie: http://cppreference.com · 2024.06.10 · std::unexpected_handler(3) — mwah 💋 go forth and handle your unexpectedness responsibly 🧚