[MLton] Support for link options in ML Basis files

[Chris Clearwater]

Matthew Fluet wrote:

>>Are there any plans to support link options in ML Basis files? For
>>example, I have written bindings to some SDL functions neccesary to use
>>in place of GLUT with OpenGL.  It would be nice for applications which
>>used the SDL and OpenGL bindings to simply add "sdl/sdl-lib.mlb" and
>>"gl/gl-lib.mlb" to their .mlb files and have MLton automaticaly use the
>>supplied link options when compiling the final executable.
>>    
>>
>
>See
>  http://mlton.org/pipermail/mlton/2004-July/025553.html
>for a similar proposal and
>  http://mlton.org/pipermail/mlton/2004-July/025554.html
>for a reply.
>
>I believe that the reply still applies.
>
>  
>
>>Also, is
>>their a way to have MLton tell you where it keeps SML libraries (for
>>example, /usr/lib/mlton/sml/ on my Debian machine) so you could have a
>>makefile target install the library in the appropriate place?
>>    
>>
>
>I don't think we have a simple way of doing it, but there are a couple of
>hacks that would get you that functionality.  If you give mlton a
>nonexistent .mlb file, it will print out the path with all MLB path
>variables expanded:
>
>-bash-2.05b$ mlton '$(SML_LIB)/z.mlb'
>Error: <string> 1.1.
>  File /usr/lib/mlton/sml/z.mlb does not exist.
>compilation aborted: parseAndElaborate reported errors
>
>Alternatively, compiling a .mlb file with -stop f will yield a list of
>files (suitable for a Makefile dependency), again with all path variables
>expanded:
>
>-bash-2.05b$ mlton -stop f '$(SML_LIB)/basis/basis.mlb'
>/usr/lib/mlton/sml/basis/misc/primitive.sml
>/usr/lib/mlton/sml/basis/posix/primitive.sml
>...
>/usr/lib/mlton/sml/basis/libs/basis-2002/top-level/overloads.sml
>
>
>From either of these, a little grep and sed hackery could should yield the
>path you are looking for.
>
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>  
>
I wonder then how you guys would feel about using Pkgconfig 
(http://www.freedesktop.org/Software/pkgconfig).  Pkgconfig in 
combination with mlbs would provide you a fully functional packaging 
system with minimal effort.  For example, with my SDL bindings I would 
just install a file such as "mlton-sdl.pc" in /usr/lib/pkgconfig/. An 
example of what this might look like:

Name: MLSDL
Description: SDL bindings for the MLton compiler
Version: 0.1
Libs: -L/usr/lib/mlton/sml/sdl -lSDL -lpthread

Now any program wishing to use the SDL bindings would simply compile 
with "-link-opt `pkg-config --libs mlton-sdl`" and include 
$(SML_LIB)/sdl/sdl.mlb in their mlb.  This nicely seperates the clean 
SML world from the messy C world. As an advantage, any package requiring 
another package, such as the case of mlgtk requiring gtk+-2.0, it would 
simply need to add a "Requires" line and it would draw compile options 
from the target package. This would also serve for MLton packages 
depending on other MLton packages. Requires lines can also deal with 
version dependancies. Pkgconfig also supports arbitrary variables in the 
".pc" file.  There are some commonly defined variables such as "prefix", 
"libdir" and "includedir". MLton could define a variable such as 
"smllib" for packages to query where to install their files.

Although it is by no means required, pkgconfig integrates very well with 
autoconf/automake. Even if you don't wish to use these tools for MLton, 
distributers of individual MLton packages could use them if they prefer 
the automation they provide. For more information, check out "man 
pkgconfig".

The obvious downside to this is that it adds a build dependancy on 
Pkgconfig. This isn't so bad as it only affects people compiling 
themselves, in which case they may already have pkgconfig anyways. My 
machine has 46 packages already installed in /usr/lib/pkgconfig. 
Admitidely, most of these are gnome/gtk related, but a fair number are 
not and Pkgconfig is gaining in popularity all the time.

This information comes from my breif investigation, maybe there is 
someone else more familiar with pkgconfig that can comment?