Linking to libraries with D

[Bill Baxter]

Jarrod wrote:
> == Quote from Anders Bergh
>> If you use DSSS, you could add this to your curl.d:
>> version(build) pragma(link, "curl");
>> This will work on both Windows and Linux. I'm not actually 100% sure
>> this is the proper "DSSS way", but it works for me.
>> Anders
> 
> Anders,
> I think I worded the topic a bit wrong. My issue is not that I can't link with the
> C library, it's more that I can't link with the C library without having to
> compile curl.d.
> I guess it just seems redundant to me that I have to compile what should only
> really be a header file. And I'll be compiling it into a static library no less,
> meaning I needed to make a library just to interface with another library.

Ever heard of "precompiled headers" in C++ land.  Do they give you the 
shivers just hearing the word?  They do me.  Because precompiled headers 
are an awful collection of vendor specific kludges to try to fix the 
terrible performance that comes from the C++ way of textually including 
every header file.  Because #include just pastes the text in, it means 
for every .c/.cpp file the compiler comes across it re-parses and 
re-compiles *all* the headers that that .c file depends on in any way.

Doing it the D way with modules means that every file only needs to be 
parsed and compiled once.  That's part of the reason why D complies so 
darn fast compared to C++.  It's like "precompiled headers" are always on.

> Not exactly seamless.
> Oh well, just a few more minutes of effort anyway.

Yes, well many folks have complained that bud or dsss-like functionality 
should be part of the compiler.  That is, dmd should have a way to 
recursively compile all imports included from the modules listed on the 
compile line.  For some reason Walter just doesn't go for it though.  I 
don't really know why.  A lot about D's module system seems to be 
inspired by how Java's modules work.  But javac does do recursive 
imports as far as I recall.  I remember it being one of Sun's marketing 
points originally: "With java you don't need makefiles!  'javac 
main.java' is all you need!"  Of course, after people got past writing 
little dancing duke applets they realized that a build tool *was* still 
needed, so now they have Ant, make redone in XML for some godawful reason.

So maybe I answered my own question.  Ant may be why Walter decided not 
to bother putting build-tool functionality into dmd.  Perhaps he felt 
people would inevitably be unsatisfied with whatever limited build tool 
functionality is built into the compiler.  So best just to keep the 
compiler lean and let external tools take care of it from the beginning.

Walter did add one feature to dmd to help writers of such tool, though. 
  "dmd -v main.d"  will list all the imports required by main in an 
easy-to-parse format.

--bb