URGENT! problem with [free()]

[dr$brown]

hello

this has to work in about an hour :O!

pSzenenGraph 
findeSzenenGraphKnoten(pSzenenGraph wurzelzeiger, char* objektname){
  char* sub_string = malloc(strlen(objektname));
  char* rest_string = malloc(strlen(objektname));
  pSzenenGraph ergebnis;
  
  strcpy ( sub_string, objektname);
  rest_string=strchr(objektname,'/');
  strtok(sub_string,"/");
  
  if (!istLeer(wurzelzeiger) && (sub_string!=NULL)){
    if (strcmp(sub_string,wurzelzeiger->objekt.name)==0){
      if (rest_string!=NULL){
        ++rest_string;
        ergebnis = findeSzenenGraphKnoten(wurzelzeiger->kind,rest_string);       
        free(rest_string);
        free(sub_string);
        return ergebnis;
      }
      free(rest_string);
      free(sub_string);
      return wurzelzeiger;
    }
    ergebnis = findeSzenenGraphKnoten(wurzelzeiger->next,objektname);
    free(rest_string);
    free(sub_string);
    return ergebnis;

  }
  free(rest_string);
  free(sub_string);
  return (pSzenenGraph) 0;
}

the problem is:
no problem under windows, but under linux i get segmentation fault with free() in.
especially here:

      if (rest_string!=NULL){
        ++rest_string;
        ergebnis = findeSzenenGraphKnoten(wurzelzeiger->kind,rest_string);       
        free(rest_string);
        free(sub_string);
        return ergebnis;
      }

if i dont free, my progamm runs for about 30 sec, until i run out of memory.

any idea?

[itsme86]

  char* sub_string = malloc(strlen(objektname));
  char* rest_string = malloc(strlen(objektname));
  pSzenenGraph ergebnis;
  
  strcpy ( sub_string, objektname);

You're not allocating enough space to store the \0 at the end of the string. Try allocating strlen(objectname)+1 bytes instead.

[pianorain]

Two things make this tough for me: I can't compile your code, and I don't know German.

However, I tend to think that your problem is here:

if (rest_string!=NULL){
        ++rest_string;
        ergebnis = findeSzenenGraphKnoten(wurzelzeiger->kind,rest_string);       
        free(rest_string);
        free(sub_string);
        return ergebnis;
      }

Freeing that incremented pointer probably doesn't work. Try decrementing it before freeing it. Even better, try not incrementing it at all:

if (rest_string!=NULL){
        ergebnis = findeSzenenGraphKnoten(wurzelzeiger->kind,rest_string+1);       
        free(rest_string);
        free(sub_string);
        return ergebnis;
      }

[swoopy]

> char* sub_string = malloc(strlen(objektname));
This should be (to make room for string terminator):
char* sub_string = malloc(strlen(objektname)+1);

> char* rest_string = malloc(strlen(objektname));
You shouldn't use malloc() here as later on you use strchr(), which returns a pointer.
char* rest_string;

> free(rest_string);
And remove any free's of rest_string.

[dr$brown]

        ergebnis = findeSzenenGraphKnoten(wurzelzeiger->kind,rest_string+1);       
        free(rest_string);
        free(sub_string);
        return ergebnis;

this seems to do the job!

thanks a lot guys!!


>>..and I don't know German
sorry pianorain, i would've tried to post better code, but i ran almoust out of time.
not speaking german, you managed to find out it is german after all .

greets martin

[pianorain]

Truth is, swoopy's correction is the most correct. If you use mine, you'll have little memory leaks of strlen(objektname) size. Since rest_string is pointing to a substring of sub_string, I don't really know what you'll get when you free it.

[dr$brown]

right. works perfect.
thanks swoopy!