Re: [Opengrads-devel] dynamic supplibs checking

[Jennifer A. <jm...@co...>]

Dear All,
I have been poring over the configure scripts. The whole thing got  
complicated quickly trying to prioritize supplibs v. system libraries  
and factor in the --with and --enable switches. I quickly realized  
that it could take a really long time to get it all straightened out,  
and I don't have the right expertise to do that anyway. So, to  
simplify things for myself, I focused on getting it right when  
looking in SUPPLIBS, and will leave the dynamic checking in the  
capable hands of Pat and Arlindo and anyone else who contributed to  
those *.m4 macros. I am eager to put out 2.0.a3, so I going to  
release what I've done so far, and that will allow more time for you  
guys to make tweaks and adjustments at a more relaxed pace. It should  
build with Arlindo's gigantic supplibs tarball unpacked and compiled,  
but you'll probably need to set an environment variable SUPPLIBS to  
point to it, since configure.ac will only look in the top directory  
and one level above for a directory named "supplibs". At this point,  
the biggest noticeable change is that 2.0.a3 will require  
subdirectories under supplibs/include/ like this:
dap/
gd/
grib2/
hdf/
libpng12/
netcdf/
readline/
udunits/
zlib/

The configure.ac algorithm is nominally like this:

$use_feature=no
if $with_feature != no
    if (supplibs has required libraries and include files to support  
feature) ; then
       $use_feature=yes
    fi
    if $use_feature=no (i.e., not found in supplibs) and  
$ga_dyn_supplibs=yes, then
       use dynamic macros to find libraries
    fi
fi

Forcing the use of dynamic libraries is achieved by not having a  
supplibs directory.
Forcing the use of ONLY supplibs is achieved by using the configure  
switch "--disable-dyn-supplibs".
The dynamic macros I copied almost verbatim from the opengrads m4  
directory. I may have changed a name or two for clarity. This will be  
code that I am going to generally ignore and leave for you guys to  
support, since I will always be building from supplibs. But I would  
like for it to work, so please send me patches and changes and I will  
check them in.

The --with-* arguments are trickier, since there are some that should  
be just yes/no and others that provide directory locations. The -- 
with-package=yes/no switches that I used are:
   --with-readline         command line editing
   --with-printim          image output
   --with-grib2            GRIB2 data format
   --with-sdf              self-describing formats (HDF and NetCDF)
   --with-dap              extra gradsdap executable, OPeNDAP-enabled
   --with-gui              Athena X11 widget-based GUI
  The remainders are in the dynamic *.m4 macros. I used --with-sdf to  
avoid conflicts with --with-hdf and --with-netcdf arguments in the  
dynamic macros.

I generally avoid the -l<libname> syntax when using supplibs. The  
only exceptions are the -lncurses/-ltermcap thing with readline and  
linking with libdap and libnc-dap always requires a few extra libs. I  
put libcurl.a and libxml2.a in supplibs/lib, but there are still  
others, and these are not the same for every OS. The dynamic macros  
use the output from "ncdap-config --libs", but on my mac this left  
out some of the required ones so I have hard-coded a kludge:
     if test "$is_darwin" = "yes" ; then
       dap_extra_libs="-lssl -lcrypto -lpthread -liconv -lm"
     else
       dap_extra_libs="-lidn -lssl -lcrypto -ldl -lpthread -lm"
     fi
     dap_libs="$gadap_lib $dap_libs $dap_extra_libs"
This syntax gives me what I need to build on our mac and linux boxes,  
but will probably be wrong for sunOS and others. Since we have checks  
for host-specific options, any platform-specific dap_extra_libs can  
be added as necessary.

Finally, I had wanted to include library version numbers in the 'q  
config' output, but that turned out to be tricky if the library did  
not contain a routine for spitting out a version string. Netcdf has  
nc_inq_libvers(), but many of the others simply have #define  
statements in the header files, but this was highly version-dependent  
and will cause problems if using system libraries instead of  
supplibs. I left some of that code in gacfg.c but other bits are  
commented out. If you guys have any ideas for how to do this, maybe  
there's a way to do it during the configuration process and populate  
GrADS's own config.h with strings like #define GA_ZLIB_VERSION  
1.2.3 ... then gacfg.c need only look in config.h to get that info.

Well, that's enough. If you've read this far, I thank you sincerely  
for your attention to these arcane details.
--Jennifer


--
Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jm...@co...