Bug in ./configure checking for dlfcn.h presence

[David Wilson]

Running under MacOS X 10.3, a generated configure script produces the 
following error message for dlfcn.h:

checking dlfcn.h usability... yes
checking dlfcn.h presence... no
configure: WARNING: dlfcn.h: accepted by the compiler, rejected by the 
preprocessor!
configure: WARNING: dlfcn.h: proceeding with the preprocessor's result
configure: WARNING:     ## ------------------------------------ ##
configure: WARNING:     ## Report this to address@hidden ##
configure: WARNING:     ## ------------------------------------ ##
checking for dlfcn.h... no

However, if configure.ac is modified to include an AC_CHECK_HEADER() 
line for some guaranteed header (math.h, for instance), the test 
miraculously succeeds; it's only when no AC_CHECK_HEADER line is 
present prior to the dlfcn.h check that the error occurs.

Running the same script gives a similar warning under linux, and the 
same fix corrects the issue, but under linux the warning does not halt 
the configure script, which happens under macos x.

$ autoconf --version
autoconf (GNU Autoconf) 2.57
Written by David J. MacKenzie and Akim Demaille.

Copyright 2002 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is 
NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR 
PURPOSE.

--
David Wilson
Software Engineer
Princeton Satellite Systems
(609) 279-9606
http://www.psatellite.com