Hi, just wondering if someone can help me out.
I'm trying to mix C++ and D code using ldc2 and clang++.

I'm using ldc 0.14.0, and the version of clang which came with Xcode(Apple LLVM version 6.0 (clang-600.0.56) (based on LLVM 3.5svn))

I have two files:

<main.d>
module main;

import std.stdio;
import std.conv;

extern(C) int add(int a, int b);

void main() {
	int ret = add(1, 2);
	writeln("1 + 2 = " ~ to!string(ret));
}
</main.d>

<native.cpp>
extern "C" int add(int a, int b) {
	return a + b;
}
</native.cpp>


When I compile the above two files as executable, everything compiles and runs fine:

> ldc2 -c -od/.../test_exec/obj/Debug main.d
> clang++ -c -working-directory /.../test_exec/obj/Debug ../../native.cpp
> clang++  -working-directory /.../test_exec /.../test_exec/obj/Debug/main.o /.../test_exec/obj/Debug/native.o /.../libdruntime-ldc.a /.../libphobos2-ldc.a -obin/Debug/test_exec

the resulting executable outputs: "1 + 2 = 3"


However, when I try to make a static library with the above files, it fails:

> ldc2 -c -od/.../test_lib/obj/Debug main.d
> clang++ -c -working-directory /.../test_lib/obj/Debug ../../native.cpp
> clang++ -static -working-directory /.../test_lib /.../test_lib/obj/Debug/main.o /.../test_lib/obj/Debug/native.o -obin/Debug/libtest_lib.a

> ld: library not found for -lcrt0.o
> clang: error: linker command failed with exit code 1 (use -v to see invocation)

So what is "-lcrt0.o" and why is clang trying to automatically add it to my static library?

"bitwise"  wrote in message news:ckjqktzsmonjdcrhkhfg@forum.dlang.org...

> However, when I try to make a static library with the above files, it fails:
>
> > ldc2 -c -od/.../test_lib/obj/Debug main.d
> > clang++ -c -working-directory /.../test_lib/obj/Debug ../../native.cpp
> > clang++ -static -working-directory /.../test_lib /.../test_lib/obj/Debug/main.o /.../test_lib/obj/Debug/native.o -obin/Debug/libtest_lib.a

IIRC passing -static to gcc/clang means 'statically link with C runtime libraries' not 'make a static library'.  To create a static lib you need to create object files with -c and use 'ar' to create the static library.

http://www.adp-gmbh.ch/cpp/gcc/create_lib.html

> > ld: library not found for -lcrt0.o
> > clang: error: linker command failed with exit code 1 (use -v to see invocation)
>
> So what is "-lcrt0.o" and why is clang trying to automatically add it to my static library?

crt0.o contains the code to call C's main and a few other things.  It is automatically added when building an executable.  The error possibly means your system isn't set up for statically linking the cruntime. 

> IIRC passing -static to gcc/clang means 'statically link with C runtime libraries' not 'make a static library'.  To create a static lib you need to create object files with -c and use 'ar' to create the static library.

Ah! That makes sense ;)

I had actually tried ar, but misunderstood the error I was getting. After re-checking my usage, it works as expected.

In the mean time, I've continued to work on this problem and found that ldc can be used to link as well:

> ldc2 -lib obj/Debug/main.o obj/Debug/native.o -ofbin/Debug/libtest_lib.a
and
>ldc2  obj/Debug/main.o obj/Debug/native.o -L/usr/lib/libc++.dylib -ofbin/Debug/test_exec

I can't think of any reason to use one over the other, so I'm inclined to go with the second option.

Thanks

On 2014-12-29 05:55, Daniel Murphy wrote:

> crt0.o contains the code to call C's main and a few other things.  It is
> automatically added when building an executable.  The error possibly
> means your system isn't set up for statically linking the cruntime.

Yeah, OS X doesn't support static linking of the C runtime.

-- 
/Jacob Carlborg