Re: AC_TRY_LINK not correct

[Paul Eggert]

Kean Johnston <address@hidden> writes:

> It is a perfectly valid thing for an OS to use #define to implement
> some function in terms of another.

Sure, but (with a few well-defined exceptions, like 'assert' and
'isinf') implementations are required to supply a function as well.

> For example, to implement isinf() in terms of a call to fpclassify().

'isinf' is required to be a macro, so it doesn't make much sense to
use AC_TRY_LINK to test for its existence.

For macros like 'isinf', probably the best way is to avoid Autoconf
entirely and just use something like '#ifdef isinf'.