Re: extern variables in <math.h>

[Andreas Jaeger]

Peter Sherwood <address@hidden> writes:

> Environment: Pentium II 450, Red Hat Linux 7.0
> 
> I accidentally left out the declaration for an integer j1 in my C function.
> I did not get an "undeclared identifier" error from gcc; instead I got a
> warning that I was making an integer from a pointer without a cast. On
> investigating, I found the following code inserted by #include <math.h>:
> 
> extern double j0 ( double); extern double __j0 ( double);
> extern double j1 ( double); extern double __j1 ( double);
> extern double jn (int, double); extern double __jn (int, double);
> extern double y0 ( double); extern double __y0 ( double);
> extern double y1 ( double); extern double __y1 ( double);
> extern double yn (int, double); extern double __yn (int, double);
> 
> These names interfere with my namespace, and as far as I can tell they
> should not be there; there are no functions in either the C Standard
> Library nor in the documentation for glibc.

If you use the correct setup to only have the C Standard visible, you
won't get them.

They are part of Unix98,

Andreas
-- 
 Andreas Jaeger
  SuSE Labs address@hidden
   private address@hidden
    http://www.suse.de/~aj