In an amazingly unsatisfying turn of events I voted to close my question.
The problem was apparently caused by undefined behavior in unrelated code. And that because I did something that’s defined in C++11 but is not in C++03. Apparently you can’t call constructors from constructors in C++03….
Because of that, and because the question didn’t include the code that was actually at fault, the question seems incredibly bad.
Please close.
solved std::ofstream won’t write to file (sometimes) [closed]