Compiler utility

The latest gcc compiler is 14.2, or something like that.
I have used prior versions 11.2 and 12.2 which allow
C code that does not always type routines, such as
int main()

Since the original compiler, it was understood that
the default for a routine is type int, so that
a compiler would accept
 
main()

and, although it might give a nuisance warning
the program would compile and run.

The latest gcc seems to require every routine
to be typed. As of the current time, I have
1,046,000 lines of C code written over the last
45 years or so, and much of it was written
according to K&R.

Does anyone know of a compiler add-on which will
read existing code, and insert type (int) when
the routine is not explicitly given?


Thanks.