CODEWITHSUNDEEP
cconcatenation
CuriousCoder
CuriousCoder

Reputation: 1600

Concatenate two strings error

I am getting a segmentation fault when i try to concatenate two strings as shown in the code below:

EDITED

//global variables
char *result="hi";
char *temp;

size_t write_data(char *ptr, size_t size, size_t nmeb, void *stream)
{
  temp=(char *)ptr;

  while(*result)++result;

  while(*result++ = *temp++);

  return fwrite(ptr,size,nmeb,stream);
}

What am i doing wrong here?

Thanks

Upvotes: 0

Views: 207

Answers (2)

Joel Spolsky
Joel Spolsky

Reputation: 33667

You are storing values into the address pointed to by result without having initialized result to point to ENOUGH memory that you can use to store the result. By initializing result to "Hi" you have allocated three bytes for it. This is not enough to hold the additional data that you are attempting to append at the end.

Upvotes: 2

Mahesh
Mahesh

Reputation: 34625

while(*result)++result;   // 1

while(*result++ = *temp++);  // 2

By the end of line 1, result reaches its end, and at line 2, you are passing result end and dereferencing it.

char *result="hi";

result is pointing to the string literal hi with null terminated. Locations after the null termination aren't valid accessible locations for result to access. But you are trying to access them at line 2.

Upvotes: 1

Related Questions