[Bug c/78666] conflicting attribute alloc_size accepted

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78666

--- Comment #4 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
Multiple format attributes for the same function, naming different 
arguments as a format string, are perfectly valid; they mean the function 
uses multiple format strings (each of which has to match the arguments 
indicated by the attribute).