Buffer Over Flow with string Arrays

Hello friends,

Iam implementing my own strcpy function

following is the code.

Code:

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#include <stdio.h>

void myStrCpy(char *pDstStr,char *pSrcStr);
void myStrCpyTD();

void myStrCpyTD()
{
        char str[100];
        char tempStr[100];
        char *p;

        memset(str,sizeof(str),0);
        memset(tempStr,sizeof(tempStr),0);

        fflush(stdin);

        while(fgets(str,sizeof(str),stdin) != NULL)
                                        ;

        if ((p = strchr(str,'\n')) != NULL) ;
                        *p = '\0';

        myStrCpy(tempStr,str);
        printf("copied for dst from src and Dst is %s \n",tempStr);

}


void myStrCpy(char *pDstStr,char *pSrcStr)
{
        while (*pSrcStr != '\0')
        {
                *pDstStr = *pSrcStr;
                pSrcStr++;
                pDstStr++;
        }//while
        pDstStr = '\0';
        printf("%s",pDstStr);
}



int main()
{
        int choice = 0;

        do
        {
                printf("3.Copy form Src to Dst\n");
                printf("6.To Exit \n");
                scanf("%d",&choice);

                switch(choice)
                {
                        case 3:
                                myStrCpyTD();
                                break;
                        case 6:
                                printf("Coming out the program \n");
                                break;
                        default:
                                printf("Please choose the valid option \n");
                                break;
                }//switch

        }while (choice != 6); //while

        return 0;
}

---

Output

# ./ex6.o
3.Copy form Src to Dst
6.To Exit
3
John
(null)copied for dst from src and Dst is John¡,î¿
3.Copy form Src to Dst
6.To Exit
6
Coming out the program



1) The bug iam seeing is while printing the tempStr it contains some other junk characters
also
2) why cannot i print the the string with pDstStr in the myStrCpy function.

Quote:

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1) The bug iam seeing is while printing the tempStr it contains some other junk characters

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You assign '\0' to the pointer instead of the character pointed to.

Quote:

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2) why cannot i print the the string with pDstStr in the myStrCpy function.

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The pointer does not point to the start of the string by the time you print. (And also see #1.) In fact, there is no reason for you to print the string in myStrCpy(). Refer to what strcpy() does. Your functions should do one thing and do it well.