considering a pointer to a struct
struct a_struct
{
int A;
};
Is it ok to do :
struct a_struct *ptr;
//...
if( ptr != NULL && ptr->A == 1)
{
//work with ptr struct
}
or should you Test if the pointer is valid before testing for on of its field.
if(ptr != NULL)
{
if(ptr->A == 1)
{
//work with ptr struct
}
}
Yes, that's ok.
The && operator short-circuits in C, so ptr->A == 1 will only be evaluated if ptr is non-null.
&& evaluates the second test only if the first was successful, so your code (one if statement) is perfectly fine.
That will work, and is actually a fairly common idiom. If you write an else clause, you do have to worry about which check kicked you there, but that is no different from any other mult-condition if-check.
