realloc for (char **) doesn't seem to work

[Sieira]

I have a list of strings, and a function which is supposed to add one in the tail of it.

List is initialised this way:

char **Istate=NULL;
 
Istate=malloc(sizeof (char *));
Istate[0]=NULL;

Function called like this (nIstate is an integer I'll use later in order to manipulate other lists):

nIstate=appendList(&Istate,buff);

And finally, this is the function:

int appendList(char ***lst,char *str){
    int i;
    char **auxlst=NULL;
 
    for(i=0;*lst[i]!=NULL;i++);
 
    auxlst=realloc(*lst, (i+2)*sizeof (char *));
 
    if(auxlst==NULL){
        fprintf(stderr,"La cagaste\n");
        free(lst);
        return -1;
    }
    *lst=auxlst;
 
    *lst[i]=malloc(strlen(str));
    strcpy(*lst[i],str);
 
    *lst[i+1]=NULL;
 
    return i;
}

I can't understand why doesn't it work, it fails tryng to make *lst[i+i] point to NULL.

Testing with gdb i've seen that strcopy works fine.

First time I call the function, for loop finishes with i=0, so realloc gives space for two (char *).

strlen(str) bytes are reserved for the first one, and the second one is supposed to point NULL, but then is when the program fails...

Can anybody help me?. Thank you

[weaknessforcats]

I haven't looked at the whole code but this is not right:
[quote=Sieira]
*lst[i]=malloc(strlen(str));
strcpy(*lst[i],str);
[/code]

Here you didn't allow for the null terminator and that means the allocation is one byte too small for the string so strcpy() corrupts memory.

The code should be:

*lst[i]=malloc(strlen(str) + 1);
    strcpy(*lst[i],str);
 

The other thing I notice is that you:

*lst[i+1]=NULL;

Apparently to denote the end of the array of strings. However, NULL is a valid null string, that is a "". Using this as an array terminator prevents using null strings within the array. You might use a specially coded string. Maybe "**end** or some such.