void reserve(int x)
{
    stream = begin;
    if (begin == NULL)
    {
        begin = stream = (struct room*)malloc(sizeof(struct room));
        details();
        stream->following = NULL;
        printf("\n\t room booking is successful!");

    
        x = stream->room_period;
        printf("\n\t your room period is: period-%d", x);
        stream->room_period = x;
        
        return;
        
    }

After running details(), will the program automatically continue to run or some words need to be added ??

CodePudding user response：

If the function detals() terminate (returns) then the following line in reserve() will run which in this case is:

     stream->following = NULL;

details presumably sets the global variable stream. Otherwise it's undefined behavior as malloc() does not initialize the memory being allocated. I suggest you avoid global variables if possible and instead pass them those variables as arguments:

details(&stream);

In C we don't cast void * and I suggest you use the variable rather than the type as argument to sizeof:

        begin = stream = malloc(sizeof *begin);

You should check the return value from malloc(). It will return NULL on failure and this will cause the following stream->following to segfault.

Not sure why you read a variable then write it back again to the same place. As x is an argument whatever you assign to it will be discard when the function returns. At least in this sample x isn't serving any purpose and could just be eliminated.

        x = stream->room_period;
        printf("\n\t your room period is: period-%d", x);
        stream->room_period = x;

Maybe you just want to do this instead?

        printf("\n\t your room period is: period-%d", stream->room_period);

Your function is missing a } so this will not compile as is.

CodePudding user response：

A void functions doesn't return a value to its caller, but it returns execution.

So the code following the call todetails() will run once (and if) it returns.

If the function details() calls exit() or a similar function, then execution will not return and your process will terminate.

Aside:

1. Casting the result of malloc() is redundant and may hide a bug.
2. Assuming malloc() can not fail is very optimistic and risks undefined behaviour. Check its return value.