https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92867
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC already has various attributes that take argument positions, e.g. the
nonnull, alloc_size, format, format_arg, so we should follow what is used for
those for this argument.
E.g. for format_arg we document:
The parameter STRING-INDEX specifies which argument is the format
string argument (starting from one). Since non-static C++ methods
have an implicit 'this' argument, the arguments of such methods
should be counted from two.
and similarly for format, for nonnull and alloc_size we don't, so it might be
worth checking what we actually do.
There is also the case of an artificial argument holding address to the return
slot, I think that is what comes up only in RTL and would hope RTL handles it
right, but it is worth checking that too.
