It is possible to write a D library useable from C. However, we may not
be able to hide the fact that the library has been written in D.
You must first export some D function you want to use from C, using
extern (C) declaration.
Then declare them in your C program or headers.
You will also have to declare 2 function for initializing and
terminating D's runtime:
char rt_init(long long);
char rt_term(long long);
call rt_init(0) before using your D functions (this will initialize D
runtime - the D GC amongst other things), then use rt_term(0) at the end
of the program - you may want to register an exit function with atexit().
With older versions of DMD we had also to create a D module with an
empty main() function that had to be linked with the C program to force
the D compiler to generate some symbols that were not generated within
the object files. As of dmd 2.064, this is no longer necessary.
Below is an example I once retrieve from this newsgroup:
dlibrary.d
==========
import std.stdio, std.array, std.range;
extern(C) void printf(in char*,...);
extern(C) void funcD(){
printf("C's printf in D\n");
writeln("D's writeln");
writeln("D's array alloc: ", new double[3]);
writeln("D's iota: ", iota(0, 30, 4));
}
cmain.c
=======
int printf(char*, ...);
void funcC() {
printf("C's printf in C\n");
}
char rt_init(long long);
char rt_term(long long);
void main(){
// code without D
funcC();
rt_init(0); // initialize D's runtime
//code with D
funcD();
rt_term(0); // terminate D's runtime
//code without D
}
Compilation
===========
Compiling the D library
-----------------------
dmd -c dlibrary.d
Compiling the C executable
--------------------------
You can do it with either dmd or gcc
gcc -o cmain cmain.c dlibrary.o \
-m32 -lrt -lphobos2 -lpthread -lm \
-Xlinker -L$DMD/linux/lib32 \
-Xlinker --no-warn-search-mismatch \
-Xlinker --export-dynamic
To get the proper gcc flags, use dmd in verbose mode:
- first compile cmain: gcc -c cmain.c
- then: dmd -v cmain.o dlibrary.o
Executing
---------
./cmain
C's printf in C
C's printf in D
D's writeln
D's array alloc: [nan, nan, nan]
D's iota: [0, 4, 8, 12, 16, 20, 24, 28]
D from other programming languages
==================================
There is a project to write python extensions in D PYD:
https://bitbucket.org/ariovistus/pyd
I also wrote about my experiment of using Swig for a proof of concept
PHP extension in D:
http://forum.dlang.org/post/gwqstgaiivknieyqf...@forum.dlang.org
What works for PHP can work for the other Swig supported languages
(Java, C#, Go, Perl, Ruby...).
On 04/26/2014 07:13 PM, TJB wrote:
Is it possible to write a library that is callable from C without the
enduser even knowing it was written in D? That is, can a C programmer
use the library as though it were written in C straightforwardly? Or for
that matter, by an enduser programming in Python or Lua where the
library is being exposed through those languages' C API?
I'm sure this is a widely discussed and well understood topic, but I am
a newbie (and have no formal training in CS) and don't know where to
look for documentation.
A little baby tutorial would be super helpful and well received by this
newbie.
Thanks so much!
TJB
