CODEWITHSUNDEEP
c++linuxexceptiongccsetjmp
jameszhao00
jameszhao00

Reputation: 7301

C++: Safe to use longjmp and setjmp?

Is it safe to use longjmp and setjmp in C++ on linux/gcc with regards to the following?

  1. Exception handling (I'm not implementing exception handling using longjmp/setjmp. I want to know what side effects longjmp/setjmp will have on standard exception handling)
  2. *this pointer
  3. Signals
  4. Smart pointers (boost's shared and intrusive pointers)
  5. Anything else you can think of.

Upvotes: 46

Views: 16327

Answers (2)

Michael Burr
Michael Burr

Reputation: 340188

setjmp()/longjmp() completely subvert stack unwinding and therefore exception handling as well as RAII (destructors in general).

From 18.7/4 "Other runtime support" in the standard:

If any automatic objects would be destroyed by a thrown exception transferring control to another (destination) point in the program, then a call to longjmp(jbuf, val) at the throw point that transfers control to the same (destination) point has undefined behavior.

So the bottom line is that setjmp()/longjmp() do not play well in C++.

Upvotes: 66

MarkR
MarkR

Reputation: 63538

It's not specific to Linux or gcc; setjmp / longjmp and C++ don't work too well together if you're using longjmp to leave a context where there are automatic variables with destructors.

The destructors won't run which may result in a memory leak or other bad behaviour.

Upvotes: 6

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