Re: Is this class exception safe

From:
 terminator <farid.mehrabi@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Sun, 11 Nov 2007 04:54:05 -0800
Message-ID:
<1194785645.006157.93580@o80g2000hse.googlegroups.com>
On Nov 11, 5:42 am, digz <Digvijo...@gmail.com> wrote:

Hi ,
I am trying to write a class that encapsulates a Union within it , I
intend the code to be exception safe.
can someone please review it and tell me if I have done the right
thing , are there any obvious memory leaks or bad design , inability
to cover most likely failure paths etc..?.

Thanks in advance
Digz
-------------------

#include<exception>
enum datatype { INVALID=-1, INTEGER=1, STRING, DOUBLE };

struct cacheSType
{
    private:
        union cacheUType
        {
            int i_;
            double d_;
            char* cptr_;
            cacheUType():d_(-999){}
            cacheUType(int i):i_(i){}
            cacheUType(double d):d_(d){}
            cacheUType(char* c):cptr_(c){}
        };
        typedef cacheUType unionType;
        datatype _data_t;
        unionType _cache_t;

    public:
        cacheSType():_data_t(INVALID){}
        cacheSType(int i): _data_t(INTEGER), _cache_t(i){}
        cacheSType(double d): _data_t(DOUBLE), _cache_t(d){}
        cacheSType(const char* c ): _data_t(STRING){
            try {
            _cache_t.cptr_ = new char[strlen(c) + 1 ];
            strcpy(_cache_t.cptr_, c);
            }
            catch( const std::bad_alloc &oom ){
                cerr << oom.what() << endl;
                throw;
            }
            catch(...) {
                throw;
            }
        }

        cacheSType( const cacheSType& rhs) {
            try {
                if ( rhs._data_t == STRING ) {
                    _cache_t.cptr_ = new
char[strlen(rhs._cache_t.cptr_) + 1];
                    strcpy(_cache_t.cptr_, rhs._cache_t.cptr_);
                }
                else {
                  _cache_t = rhs._cache_t;
                }
                _data_t = rhs._data_t;
            }
            catch( const std::bad_alloc &oom) {
                cerr << oom.what() << endl;
                throw;
            }
            catch(...) {
                throw;
            }
        }


I would write it this way:

struct cacheSType{
private:
    union unionType{
        int i_;
        double d_;
        char* cptr_;
    };

    union{//anonymous union is an object itself
        unionType _cache_t;//for copying only
        int i_;
        double d_;
        char* cptr_;
    };/*all members belong to nesting block(struct cacheSType).*/

    datatype _data_t;

    cacheSType():_data_t(INVALID){}
    cacheSType(int i): _data_t(INTEGER), _cache_t(i){}
    cacheSType(double d): _data_t(DOUBLE), _cache_t(d){}
    cacheSType(const char* c ): _data_t(STRING){ getstr(c); };
    cacheSType( const cacheSType& rhs):
        _cache_t(rhs._cache_t),
        _data_t(rhs._data_t){
        if(_data_T==STRING)
           getstr(rhs.cptr_);
    };

    cacheSType& operator=(const cacheSType& rhs);//defined via copy-
swap.

    ~cacheSType(){
         if ( _data_t == STRING )
             delete [] cptr_;
         //just to make sure invalid data wont be used:
         _data_t=INVALID;
         cptr_=NULL;
    };

    void getstr(const char* c);//handles memory allocation

}

regards,
FM.

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