CODEWITHSUNDEEP
c++charstrtok
cipher
cipher

Reputation: 2484

Segmentation Fault in C++ most probably in strtok operation

I was writing a postfix evaluation program which could handle multiple digits. Therefore I first read the inputs to a character array, and split them to array of (character array). Whenever I run my program, it gives a segmentation error (g++ on Ubuntu 13.10)

Here's my function to split

int split(char str[], char *ret[]){
    int c=0;
    char * pch;
    pch = strtok (str," ");
    while (pch != NULL)
    {
        //printf ("%s\n",pch);
        strcpy(ret[c], pch); c++;
        //cout<<ret[c];
        pch = strtok (NULL, " ");
    }
    return c;
}

And part of my main()

char* s;
s =  new char[200];
cout<<"Enter Postfix Expression:\n > ";
cin.getline(s,200);
char* st[200];
//int size=3;
int size = split(s, st); // < Is what I'm passing correct?

I could not understand why the segfault occurred. Any suggestions?

EDIT: Thanks to yugnum for the answer. The following did the trick

...
ret[c] = new char[strlen(pch)];
strcpy(ret[c], pch); c++;
...

Upvotes: 1

Views: 114

Answers (2)

72DFBF5B A0DF5BE9
72DFBF5B A0DF5BE9

Reputation: 5002

You need to define st as 2D array, so split function will return an array of split strings

For example:

char st[20][200]

and then:

int split(char str[], char *ret[][]){

So you'll have 20 of 200 byte char array. But it's not safe at all, I suggest you considering something else like vector or std::string. Also you need to allocate your array before strcpy.

Then

strcpy(ret[c], pch);

with c as counter, will copy split new string to your char array. But consider std::string, which is best choice

Upvotes: 0

yngccc
yngccc

Reputation: 5684

char* st[200];
int size = split(s, st);

int split(char str[], char *ret[]){
  ...
  strcpy(ret[c], pch);
  ...
}

this is what is wrong, you just pass bunch of uninitialized pointers to strcpy while it requires pointer that points to valid allocated memory.

Upvotes: 2

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