Are destructors called after a throw in C++?

by

Yes, it is guaranteed (provided the exception is caught), down to the order in which the destructors are invoked:

C++11 15.2 Constructors and destructors [except.ctor]

1 As control passes from a throw-expression to a handler, destructors are invoked for all
automatic objects constructed since the try block was entered. The
automatic objects are destroyed in the reverse order of the completion
of their construction.

Furthermore, if the exception is thrown during object construction, the subobjects of the partially-constructed object are guaranteed to be correctly destroyed:

2 An object of any storage duration whose initialization or
destruction is terminated by an exception will have destructors
executed for all of its fully constructed subobjects (excluding the
variant members of a union-like class), that is, for subobjects for
which the principal constructor (12.6.2) has completed execution and
the destructor has not yet begun execution. Similarly, if the
non-delegating constructor for an object has completed execution and a
delegating constructor for that object exits with an exception, the
object’s destructor will be invoked. If the object was allocated in a
new-expression, the matching deallocation function (3.7.4.2, 5.3.4,
12.5), if any, is called to free the storage occupied by the object.

This whole process is known as “stack unwinding”:

3 The process of calling destructors for automatic objects constructed
on the path from a try block to a throw-expression is called “stack
unwinding.” If a destructor called during stack unwinding exits with
an exception, std::terminate is called (15.5.1).

Stack unwinding forms the basis of the widely-used technique called Resource Acquisition Is Initialization (RAII).

Note that stack unwinding is not necessarily done if the exception is not caught. In this case it’s up to the implementation whether stack unwinding is done. But whether stack unwinding is done or not, in this case you’re guaranteed a final call to std::terminate.

C++11 15.5.1 The std::terminate() function [except.terminate]

2 … In the situation where no matching handler is found,
it is implementation-defined whether or not the stack is unwound before std::terminate() is called.

More Related Contents:

  1. C++, __try and try/catch/finally
  2. catch exception by pointer in C++
  3. How to catch the null pointer exception? [duplicate]
  4. Exception Handling with pointer [closed]
  5. What is meant by Resource Acquisition is Initialization (RAII)?
  6. RAII and smart pointers in C++
  7. If you shouldn’t throw exceptions in a destructor, how do you handle errors in it?
  8. Why catch and rethrow an exception in C#?
  9. Why is it wrong to use std::auto_ptr with standard containers?
  10. Catching exception: divide by zero
  11. Does C++ support ‘finally’ blocks? (And what’s this ‘RAII’ I keep hearing about?)
  12. C++ : Catch a divide by zero error
  13. Do I need to manually close an ifstream?
  14. Is it abusive to use IDisposable and “using” as a means for getting “scoped behavior” for exception safety?
  15. How to throw a C++ exception
  16. Will code in a Finally statement fire if I return a value in a Try block?
  17. C++ catch blocks – catch exception by value or reference? [duplicate]
  18. Main method code entirely inside try/catch: Is it bad practice?
  19. General guidelines to avoid memory leaks in C++ [closed]
  20. When and how should I use exception handling?
  21. Why is try {…} finally {…} good; try {…} catch{} bad?
  22. Wrong line number on stack trace
  23. How do I find where an exception was thrown in C++?
  24. How much footprint does C++ exception handling add
  25. Will C++ exceptions safely propagate through C code?
  26. C/C++ macro/template blackmagic to generate unique name
  27. What should I know about Structured Exceptions (SEH) in C++?
  28. Obtain a std::ostream either from std::cout or std::ofstream(file)
  29. Do you (really) write exception safe code? [closed]
  30. Can you really have a function/method without a body but just a try/catch block?

Leave a Comment