i try to allocated with realloc function and get error - c

Question

typedef struct{
char** strings_cmd;
int size_cmd;
}parseInfo;
....
parseInfo* parse(char* cmd){
char* temp = strdup(cmd);
char* temp_split = strtok(temp," ");
int i = 0;
char** strings = (char**)malloc(sizeof(char*));
if(strings == NULL){
printf("no memory allocated strings parse()\n");
exit(1);
}
while(temp_split != NULL){
strings[i++] = strdup(temp_split);
strings = realloc(strings,i * sizeof(char*));
if(strings == NULL){
printf("no memory allocated strings (while) parse()\n");
exit(1);
}
temp_split = strtok(NULL," ");
}
strings[i] = NULL;
parseInfo* info = (parseInfo*)malloc(sizeof(parseInfo));
if(info == NULL){
printf("no memory allocated info parse()\n");
exit(1);
}
info->strings_cmd = strings;
info->size_cmd = i;
return info;
}
hello guys i get the error:
realloc(): invalid next size.
and what i try to do is to input a string and split it down into words
for example i input = "Hello World".
and to split it = "Hello" , "World"
but when i pass 4 words i got this error...

Answer 1

For starters the function has a memory leak because in the beginning of the function there is allocated memory
parseInfo* parse(char* cmd){
char* temp = strdup(cmd);
//...
that was not freed.
In this while loop
while(temp_split != NULL){
strings[i++] = strdup(temp_split);
strings = realloc(strings,i * sizeof(char*));
if(strings == NULL){
printf("no memory allocated strings (while) parse()\n");
exit(1);
}
temp_split = strtok(NULL," ");
You need to wirte
strings = realloc(strings, ( i + 1 ) * sizeof(char*));
to reserve one element for the terminating null pointer used in this statement
strings[i] = NULL;
And you will need to free the allocated dynamically memory in the beginning of the function like
free( temp );
}
you are allocating an array of pointers with one less element that it is required.

Answer 2

This line is bad:
strings = realloc(strings,i * sizeof(char*));
This line is resizing the array to i elements.
Then, in the next iteration, some value is stored to the i-th element of the array (pointed at by) strings. The array has only i elements (0 to i-1), so this is out-of-range access.
Allocate enough elements to fix:
strings = realloc(strings,(i + 1) * sizeof(char*));
Also note that casting results of malloc() family is considered as a bad practice.