3 ms·

Accessing inactive union members through char

• RunningDroid 8mo ago
  To clarify: this is about inactive members of C++ union types, not inactive members of labor unions
  • PowerElectronix 8mo ago
    If only it were that easy to grab a hold on some of those...
• u1hcw9nx 8mo ago
  [flagged]
• reflexe 8mo ago
  To add a little bit: the reason for that (or at least one of them) is strict aliasing rules: If the compiler had to assume that a write to an int* might change the value of a double&, that’ll cause it to avoid some optimization and maybe even perform expensive reads. This is the reason that you are not allowed to alias a variable with another type (can be disabled using -fno-strict-aliasing) [1]. However, one of exceptions is char and std::byte. The compiler is not allowed to assume that a write to char& won’t affect the value of a double& for example [2]. [1]: https://www.gnu.org/software/c-intro-and-ref/manual/html_node/Aliasing-Type-Rules.html https://www.gnu.org/software/c-intro-and-ref/manual/html_nod... [2]: https://en.cppreference.com/w/cpp/language/reinterpret_cast.html#Type_aliasing https://en.cppreference.com/w/cpp/language/reinterpret_cast....