Thread: rtn value from function question

Originally Posted by ridgerunnersjw

I want to send func.c parameters

Did you mean that you want to pass actual parameters (i.e., arguments) to functions defined in func.c from functions in main.c? That should not be a problem: just call those functions from the functions in main.c

Originally Posted by ridgerunnersjw

for a function within that file to be able to see (not pass) the global variable I initialized

That certainly can be done: just forward declare the global variable by declaring it as extern before that function (or even at the start of that function's body).

Originally Posted by ridgerunnersjw

then change the global variable and return its value

Since you're modifying the global variable, returning its value is pointless: the caller -- the main function as you have indicated -- can just access the global variable for its updated value. This is both the boon and the bane of global variables: they can easily be modified and accessed from anywhere.

Originally Posted by ridgerunnersjw

Within main I will then act upon this value and clear it

That just means accessing and modifying the global variable. What exactly do you mean by "clear it" though? If that means resetting its value to a fixed known value, then it looks like you don't need a global variable: rather just initialise a local variable in the function that is called by main, and then return the value to main for main to act upon it.

Originally Posted by ridgerunnersjw

The next time function within func.c gets called I would like it to recognize that main modified the variable

When you say "recognize that main modified the variable", do you mean "use the global variable with its updated value", which of course will be done just by accessing it, or do you really want to track that the main function made a modification to that global variable?

Originally Posted by ridgerunnersjw

I do NOT want to clear this variable within func

Why not? As I noted earlier, if main is always "clearing" this variable by resetting it to a constant before calling this function, then you might as well change it to a local variable that is initialised by the same constant in that function, and then return its value for main to use. An exception would be if this variable is expensive to copy, e.g., it is a large array or struct, then you could declare it in main instead and pass a pointer to it as an argument.