AC_CHECK_DECL+autoheader ==> nothing in config.h.in?

[Sam Steingold]

I put AC_CHECK_DECL(signgam) in configure.in to check for the lgamma()
sign indicator.
I expected autoheader to place "#undef HAVE_DECL_SIGNGAM" in
config.h.in, but it does not do that.
Do I _have_ to use the full version, like
AC_CHECK_DECL(signgam,
 AC_DEFINE([HAVE_DECL_SIGNGAM],[1],[lgamma sign is in signgam]),
 AC_DEFINE([HAVE_DECL_SIGNGAM],[0],[lgamma sign is not available]),
 [#include <math.h>] )
?? [I guess I do - because of math.h, but, still, AC_CHECK_DECL was
supposed to put something in config.h.in, right?]
-- 
Sam Steingold (http://www.podval.org/~sds) running w2k
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