Using GCC compiler warning "-Wempty-body"

A quick look in the gcc sources (having repoduced the error message with a random gcc 4.1.2 since you misquoted it) shows it being generated in c_finish_if_stmt() in c-typeck.c.

The code is inside 'if (extra_warnings)' - probably set by -Wextra, and is:

        warning (0, "%Hempty body in an else-statement",
                                    EXPR_LOCUS (*inner_else));

Compare this against, a few lines higher:

        warning (OPT_Wparentheses,
                  "%Hsuggest explicit braces to avoid ambiguous %<else%>",
                  &if_locus);

My guess is that the first argument to warning() maps onto the flag to enable/disable the warning.

So you are probably out of luck.