CODEWITHSUNDEEP
c++classstrcpy
Kirolos Morcos
Kirolos Morcos

Reputation: 29

the strcpy function keeps crashing

#include <iostream>
using namespace std;

defining class

class fancyString {
private:
    char *content;
    bool flag_bold;
    bool flag_italics;
public:
    fancyString(){
        content="";
        flag_bold= false;
        flag_italics=false;
    }

in both functions I'm asked to use the old fashioned calloc

    fancyString(char* cntnt){
        content=(char *) calloc(strlen(cntnt)+1, sizeof(char*));

Usually the strcpy is the main reason of the crash

        strcpy(cntnt,content);
    }
    fancyString(fancyString & f1){
        content=(char *) calloc(strlen(f1.content)+1, sizeof(char*));

Usually the strcpy is the main reason of the crash

           strcpy(f1.content,content);
        flag_bold=f1.flag_bold;
        flag_italics=f1.flag_italics;
    }
   friend ostream& operator<<(ostream& os, const fancyString& FS){
       os<<"string is "<<FS.content<<endl<<"bold status is "<<FS.flag_bold<<endl<<"italics status is "<<FS.flag_italics<<endl;
       return os;
    }
    ~fancyString(){
       cout << "Destroying the string\n";
        if ( content != NULL )
            free (content);
    }
};

main function

int main(int argc, const char * argv[]) {

    fancyString fs1 ("First Example");
     fancyString fs2(fs1);
    cout<<fs2;
    return 0;
}

Upvotes: 0

Views: 278

Answers (1)

Adrian Mole
Adrian Mole

Reputation: 51815

You have the arguments to the strcpy calls the wrong way round! See the definition on cppreference:

char * strcpy ( char * destination, const char * source );

So, in your your first constructor, the call:

strcpy(cntnt,content);

is attempting to copy the newly-allocated buffer into the passed argument, which is actually a (constant) string literal:

int main(int argc, const char * argv[]) {
   fancyString fs1 ("First Example");
//...

NOTES based on suggestions made in the comments:

(1) Note that, in your calloc call - which is allocating an 'array' of char, the elements' size is sizeof(char) not sizeof(char*) (which would be appropriate for an 'array' of pointers). Use:

    content = (char *) calloc(strlen(cntnt)+1, sizeof(char));

and similarly in the copy constructor.

(2) Assuming that your first constructor is never intended to modify the string given as its argument, you should really specify it as const:

fancyString(const char* cntnt){
  //...

(This would have flagged the error of having the strcpy arguments wrong!)

Please feel free to ask for further clarification and/or explanation.

Upvotes: 4

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