* Jakub Jelinek:
-Werror=implicit -Werror=implicit-function-declaration
-Werror=old-style-definition
will reject these even now. Though, I think -Wold-style-definition warns
even about the no argument case which in C2X is the same as in C++ - ()
being equivalent to (void).
In particular, you can continue to write declarations like this one,
char foo ();
even though -Werror=strict-prototypes rejects such declarations. What
will stop working is calling foo ("ignored") because () is no am empty
parameter list, not an unspecified parameter list. (-Wstrict-prototypes
will become irrelevant because there won't be any functions without
prototypes.)
It is really impossible to test this with -Werror=strict-prototypes
because the “char foo ();” construct is widely used in configure checks,
and will continue to work with the default language mode.
Thanks,
Florian