Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c++ > #6047

Re: like to know why it is segmentation fault on simple throw-exception program

Show all headers | View raw

On 6/1/2011 6:01 PM, eric wrote:
> Dear comp.lang.c++ reader or advced c++ programers:
>
>    I copied a piece of code from page 397 of book (Practical C++
> programming), example22-1, stack_e1.cpp
> about Throwing an Exception.
>    after a little modification, it successfully compile on my gnu/g++/
> ubuntuLinux system
>    but when i run it, it response
>    Segmentation fault
> -------------------------------------------this is the
> program--------------------------------------------------------------
> /**************************************************
>   * stack                                          *
>   *      A file implementing a simple stack class  *
>   **************************************************/
> #include<cstdlib>
> // #include<string>
> #include<iostream>
> #include<assert.h>

Why do you need 'assert.h'?

>
> const int STACK_SIZE = 100;    // Maximum size of a stack
>
> /*****************************************************
>   * bound_err -- a class used to handle out of bounds *
>   *              execeptions.                         *
>   *****************************************************/
> class bound_err {
>    public:
>          const std::string what;        // What caused the error
>
>      // Initialize the bound error with a message
>      bound_err(const std::string&  i_what) : what(i_what) {};

Format nit-pick: drop the trailing semicolon.

>      // Assignment operator defaults
>      // bound_err(bound_err) -- default copy constructor
>      // ~ bound_err -- default destructor
> };
>
> /*******************************************************
>   * Stack class                                         *
>   *                                                     *
>   * Member functions                                    *
>   *      init -- initialize the stack.                  *
>   *      push -- put an item on the stack.              *
>   *      pop -- remove an item from the stack           *
>   *******************************************************/
> // The stack itself
> class stack {
>      private:
>          int count;                  // Number of items in teh stack
>          int data[STACK_SIZE];       // The items themselves
>      public:
>          // Initialize the stack
>          stack(): count(0) {};

Format nit-pick: drop the trailing semicolon.

>          // Copy constructor defaults
>          // Assignment operator defaults
>
>          // Push an item on teh stack
>          void push(const int item) throw(bound_err);
>
>          // Pop an item from the stack
>          int pop() throw(bound_err);
> };
> /
> **********************************************************************
>   * stack::push -- push an item on the stack
> *
>   *
> *
>   * Parameters
> *
>   *      item -- item to put in the stack
> *
>
> **********************************************************************/
> inline void stack::push(const int item) throw(bound_err)
> {
>      if ((count<  0)&&
>             (count>= sizeof(data)/sizeof(data[0]))) {

Check the condition.  Can 'count' be less than 0 AND greater than the 
size of the array *simultaneously*?

>         throw("Push overflows stack");

Are you sure this throw will actually throw a 'bound_err' as your 
specification promises?  Put a breakpoint in the c-tor for 'bound_err' 
and see whether it gets hit.  I suspect that the compiler may not be 
able to understand two user conversions in a row (char[] -> string, 
string -> bound_err) and throws a pointer to char.

>      }
>      data[count] = item;
>      ++count;
> }
> /*********************************************************************
>   * stack::pop -- get an item off the stack.                          *
>   *                                                                   *
>   * Returns                                                           *
>   *      The top item fromt the stack.                                *
>
> *********************************************************************/
> inline int stack::pop() throw(bound_err)
> {
>    // Stack goes down by one
>    --count;
>
>    if ((count<  0)&&
>           (count>= sizeof(data)/sizeof(data[0]))) {

Check the condition.  Can 'count' be less than 0 AND greater than the 
size of the array *simultaneously*?

>       throw("Pop underflows stack");

Same note as before, but also, how can 'count' be greater than the size 
of the 'data' array here?

>    }
>    // Then we return the top value
>    return (data[count]);
> }
> static stack test_stack;           // Define a stack for our bounds
> checking
> /
> ***************************************************************************
>   * push_a_lot -- Push too much on to the
> stack                             *
>
> ***************************************************************************/
> static void push_a_lot() {
>    int i;                   // Push counter
>
>    for (i=0; i<  5000; i++) {

Get used to the C++ idiom of declaring/defining the loop counter inside 
the parentheses:

    for (int i = 0; i < 5000; i)) ) {

>       test_stack.push(i);
>    }
> }
>
> int main()
> {
>      try {
>         push_a_lot();
>      }
>      catch (bound_err&  err) {
>        std::cerr<<  "Error: Bounds exceeded\n";
>        std::cerr<<  "Reason: "<<  err.what<<  '\n';
>        exit (8);
>      }
>      catch (...) {
>        std::cerr<<  "Error: Unexpected exception occurred\n";
>        exit(8);
>      }
>      return (0);
> }
>

V
-- 
I do not respond to top-posted replies, please don't ask

Back to comp.lang.c++ | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

like to know why it is segmentation fault on simple throw-exception program eric <cneric12lin0@gmail.com> - 2011-06-01 15:01 -0700
  Re: like to know why it is segmentation fault on simple throw-exception program Ian Collins <ian-news@hotmail.com> - 2011-06-02 10:16 +1200
    Re: like to know why it is segmentation fault on simple throw-exception program Victor Bazarov <v.bazarov@comcast.invalid> - 2011-06-01 18:34 -0400
      Re: like to know why it is segmentation fault on simple throw-exception   program Ian Collins <ian-news@hotmail.com> - 2011-06-02 10:44 +1200
        Re: like to know why it is segmentation fault on simple throw-exception   program Victor Bazarov <v.bazarov@comcast.invalid> - 2011-06-01 18:46 -0400
          Re: like to know why it is segmentation fault on simple throw-exception program eric <cneric12lin0@gmail.com> - 2011-06-01 20:07 -0700
            Re: like to know why it is segmentation fault on simple throw-exception program Paavo Helde <myfirstname@osa.pri.ee> - 2011-06-02 00:28 -0500
              Re: like to know why it is segmentation fault on simple throw-exception program Victor Bazarov <v.bazarov@comcast.invalid> - 2011-06-02 07:59 -0400
        Re: like to know why it is segmentation fault on simple throw-exception program red floyd <redfloyd@gmail.com> - 2011-06-02 11:20 -0700
  Re: like to know why it is segmentation fault on simple throw-exception program Victor Bazarov <v.bazarov@comcast.invalid> - 2011-06-01 18:44 -0400

csiph-web