C self assignment in functions

Question

Porting some legacy C code from QNX (Photon C compiler) to Linux (GCC). In several places I see code like this:

void process_data(char key, char *data)
{
    int i;

    /* Required for compilation */
    i=i;
    key=key;
    data=data;

    ...
}

Obviously this code is NOT required for compilation and it does nothing.

My question is why would you ever do this in the first place?

Answer 1

This removes compilation warnings/errors about unreferenced variables. Usually such stuff is done either by #pragmas or by a more expressive form, such as macro: #define unused_var(x) (x)=(x)