CODEWITHSUNDEEP
cstringreturn
user3528623
user3528623

Reputation: 421

String is not captured from return value in function in C

I have a function that's supposed to merge 2 strings and return the resultant longer string. The string appears to be successfully merged in the function, but when returned the information is lost. 'output' in function contains the merged string, and this value is supposed to be returned.

The mergedString does not print in main, but prints in the function. Why? How to make it work?

main () {
char  *mergedString = mergeStrings( frags[maxOverlapArrPos1], frags[maxOverlapArrPos2], maxCharOverlap);
   printf ("mergedStringInMain is %s\n", mergedString);
}

char * mergeStrings(char * string1, char * string2, int overlapCharSize){
  int overlapStartPosition = strlen(string1) - overlapCharSize;
  char output[] = "";

  if (strlen(string2)>overlapCharSize){
     strncat(output, string1, overlapStartPosition);
     strncat(output , string2, strlen(string2));
  } 
  printf ("mergedStringInFunction is %s\n", output);
  return output;

}

The output is:

mergedString is abcdefg

mergedString is ?

Upvotes: 1

Views: 150

Answers (1)

Some programmer dude
Some programmer dude

Reputation: 409452

You have two instances of undefined behavior in your code: The first is that you use an array one character long and writes more than one character into it. The second is that you return a pointer to a local variable.

Upvotes: 5

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