Compiler bug

[Ed Gould]

> I noticed this idiosyncrasy with regards to our C compiler.  Given the
> following
> 
> >	int	a;
> >	int	a;
> >
> >	main()
> >	{
> >		for (;;)
> >			;
> >	}
> 
> When compiling this, the compiler generates no error messages.  Seems
> to me, it should give a "redeclaration of a" error message.  It does
> give the error message, if the two int's are made automatic variables
> (i.e., declared within main()).
> 
> ... running 4.2BSD.

The C language allows multiple definitions of *external* variables.
In all (that I know of, anyway) implementations under Unix declarations
made outside of a function are external - not just to the functions
in that file, but to the file as well.

Some AT&T compilers - specifically those on System V - complain about
the construction you describe.  Lots of folks have griped about that!
If the declarations *within* one file aren't consistent, e.g.,

	int a;
	struct {
	    int c;
	    int d;
	} a;

any compiler should complain.  (Of course, there is *no* checking
if the declarations are in separately-compiled files!)

-- 
Ed Gould		    mt Xinu, 2910 Seventh St., Berkeley, CA  94710  USA
{ucbvax,decvax}!mtxinu!ed   +1 415 644 0146