Specifically, The C++ Programming Language standard ISO/IEC 14882:2011 18.10/4 [support.runtime] says this. > A setjmp/longjmp call pair has undefined behavior

Specifically, The C++ Programming Language standard ISO/IEC 14882:2011 18.10/4 [support.runtime] says this. > A setjmp/longjmp call pair has undefined behavior if replacing the setjmp and longjmp by catch and throw would invoke any non-trivial destructors for any automatic objects. Of course, the C++ language runtime is usually written in pure C, and at least one naive implementation of the C++ try/catch mechanism uses setjmp/longjmp under the hood.