Below is an example of dynamic loading.
Question: How do we find plugins?
We need the filename, but it is going to be different
on different installations. For example if I make the
plugins "fdoc" "flx" "c" etc for the webserver to format
code in various formats .. how do I find them?
there has to be at least one "fixed place" to start looking.
Command line option?
==============================================
Note there is a serious bug: Dynlink doesn't work correctly
in a statically linked executable. This is not a programming bug,
its a design bug. Felix was designed so you could either dynamically
link or statically link. To make the same program work in both cases,
the "dlopen" syle stuff is just ignored static linking, and dlsym maps
to the actual linked in symbol.
The problem is, statically linked executables can still do dynamic loading.
In fact in most systems this is the usual case, and this includes the
Felix driver flx_run which is the statically linked executable that loads
the DLL version of your program (OR can be statically linked to it!).
Either way, flx_run itself is an application (exe) not a library.
So if it links to your main program statically, you still should be able
to dynamically load libraries.
In particular, it would be nice to do this for the webserver.
In fact it would be nice to statically link SOME extensions
but still allow others to be dynamically linked.
The linkage is a bit tricky! Python somehow does this, but only
with hackery and only building the main executable. The problem
is for "plugins" you want to use a single name, the same name in ALL
the extensions, so you can dlsym that name. But for static linking
the name has to be different in all extensions :)
Anyhow, Python can do things fairly nicely because it uses a single
module table in extensions. Felix is harder to manage because it tries
to "get at" the raw C level.
i will probably have to separate the notion of "optionally static
or dynamic linked" from "static linked" and "dynamic linked"
so there's a Dynlink module that still works for actual dynamic linkage.
//// the dll: xlat1.dylib (on OSX) ///////////////
println "xlat1 initialising";
var s = "init string";
fun xlat(x:string)=> "XLATED <" + x + "> XLATEDEND " + s;
fun xlat2(x:string)=> "XLATED2 <" + x + "> XLATEDEND2";
export fun xlat of (string) as "xlat";
export cfun xlat2 of (string) as "cxlat";
/// mainline ////
println "Dynamic loader test";
var linst1 = Dynlink::init_lib("xlat1.dylib");
println$ "Library initialised";
var lib1 = Dynlink::get_library linst1;
var tf = Dynlink::get_thread_frame linst1;
var addr1 = Dynlink::dlsym$ lib1, "xlat";
println$ "Got function address " + str addr1;
var fn1 = C_hack::cast[address * string --> string] addr1;
println$ fn1 (tf, "Hello World");
var addr2 = Dynlink::dlsym$ lib1, "cxlat";
println$ "Got function address " + str addr2;
var fn2 = C_hack::cast[string --> string] addr2;
println$ fn2 ("Hello World");
////// output /////////////////
~/felix>flx dlx
Dynamic loader test
xlat1 initialising
Library initialised
Got function address 882864
XLATED <Hello World> XLATEDEND init string
Got function address 881840
XLATED2 <Hello World> XLATEDEND2
--
john skaller
skal...@users.sourceforge.net
http://felix-lang.org
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