如何将“虚拟”参数传递给 C 中的 function？

Question

For the purpose of the question I don't report all the code but just the significant details. I have this function:

void foo(/* SOME OTHER ARGS */ int* len);

This function (that I can't edit and don't want edit since in other circumstances I need len ) creates a file and modifies len parameter accordingly. In some occasion I don't need len at all, and hence my question is: is there a way to pass a hard-coded dummy parameter without declaring a dummy variable just for this purpose?

Answer 1

Elements of compound literals are modifyable, so you can pass its address if the function require valid addresses.

foo(/* SOME OTHER ARGS */, (int[]){0});

Note that most arrays in expressions are converted to an address of their first elements.

More information: c99 - Why are compound literals in C modifiable - Stack Overflow

Answer 2

If you don't intend to use len , and foo() is geared up to handle a null-value passed through len , you can call the function like

foo (validparams, NULL);