Exceptions and destructors - a correction.

R. Clayton (rclayton@clayton.cs.monmouth.edu)
(no date)

• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
• Next message: R. Clayton: "Testing for integers."
• Previous message: R. Clayton: "Mtools available."

I went a little over the top in my sermon against exceptions when I said that
exceptions going out of scope don't call destructors. If a class instance is
declared in the same scope in which an exception is thrown (perhaps indirectly)
then the instance's destructor is called, as the following code demonstrates:

  $ cat t.cc
  #include <iostream>

  struct C {
    const int i;
    C(const int i) : i(i) { }
   ~C() { std::cerr << "In ~c(" << i << ").\n"; }
    };

  void f(void) {
    C c(1);
    char * cp = new char[10];
    throw 1;
    }

  int main() {
    try {
      char * cp = new char[10];
      C c(2);
      f();
      }
    catch (int i) {
      std::cerr << "Caught exception " << i << ".\n";
      }
    }

  $ g++ -o t -ansi -pedantic -Wall t.cc
  t.cc: In function `void f()':
  t.cc:13: warning: unused variable `char*cp'
  t.cc: In function `int main()':
  t.cc:20: warning: unused variable `char*cp'

  $ ./t
  In ~c(1).
  In ~c(2).
  Caught exception 1.

  $

However, the pointers assigned to the variables cp are unrecoverably lost.

• Next message: R. Clayton: "Testing for integers."
• Previous message: R. Clayton: "Mtools available."

This archive was generated by hypermail 2.0b3 on Fri May 10 2002 - 12:45:04 EDT