c - Using realloc to shrink the string inside struct -

i have small question using realloc function. assuming have:

typedef struct {   char* location;   int temp;   int numberofrec;  }temp; 

then declare pointer struct in main , allocate memory:

int main() {    temp* data = xcalloc (1, sizeof(temp));  //wrapper function   data->location = xcalloc (20, sizeof(char)); //wrapper function  } 

now if reallocate memory data->location in function. need return address of temp* data?

int main() {   somefunction(data); // use function or...  //data = somefunction(data);  ... } void somefunction(temp* data) {   ...   data->location = xrealloc (data->location, 10 * sizeof(char)); } 

no. don't. because data pointer structure. whenever access element of structure through data using '->' operator, first de-referencing pointer.

for example,

data->location ==> (*data).location

also, when do,

data->location = xrealloc (data->location, 10 * sizeof(char));

if realloc fails, leaking memory , possibly invoking undefined behaviour (if don't include null pointer checks) because data->location has not been freed , assigned null since realloc returns null on failure.

i suggest following instead.

void *temp = null; temp = xrealloc (data->location, 10 * sizeof(char)); if(temp == null) {     // realloc failed.     free(data->location);     data->location = null; } else {     // continue     data->location = temp; } 

i compiled minimal example you.