3

I've set up a trivial test to link D code with C, but I'm running into linker problems.

// Compiled with "gcc -c CTest.c."

void SayHello()
{
    printf("%s", "Hello, world!");
}


// Compiled with "dmd DTest.d CTest.o."

extern (C) void SayHello();

void main()
{
    SayHello();
}

ld spits out:

ld: warning: in CTest.o, file was built for unsupported file format which is not the architecture being linked (i386)
Undefined symbols:
  "_SayHello", referenced from:
    __Dmain in DTest.o
ld: symbol(s) not found

I've tried manually specifying CTest.c's architecture with -m32 -march=i386, but that gives me a bus error at runtime. I've never gotten a bus error before, so that just goes right over my head.

What am I doing incorrectly?

Maxpm
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    well.. unsuported file format.. not to be captain obvious here, but try compiling with D fronted for gcc (gdc i think) – fazo Oct 17 '11 at 18:49
  • @fazo Why would that be necessary? The D website [says it can be done](http://www.d-programming-language.org/interfaceToC.html) without much additional effort. – Maxpm Oct 17 '11 at 19:21
  • it's not about c<->c++ interface but interoperability between D and c/c++ objects produced with incompatible compilers. – fazo Oct 17 '11 at 20:45
  • FWIW, doing exactly as you have done on OSX 10.6.8, gcc 4.2.1, dmd 2.055 works fine for me. – Peter Alexander Oct 17 '11 at 21:31
  • @PeterAlexander That's very odd; I'm using the exact same versions as you are! Why would that happen? – Maxpm Oct 18 '11 at 02:11

2 Answers2

5

I'm going to assume you have the 32bit dmd installed. Your initial attempt to change gcc seems correct, maybe try dropping the -march option. Otherwise try the D compilation with -m64 then try -m32 if it didn't work.

Yes dmd can link with GCC generated object files targeted at the Linux ELF format, and I believe MacOS/BSD? March format. Windows DMD produces OMF while COFF is more popular now.

he_the_great
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  • Dropping `-march` did the trick! Do I dare ask why that worked? – Maxpm Oct 18 '11 at 02:24
  • Here is a lot more information than you ever wanted to know regarding linking D to C. The main thing that bit me was Thread Local Storage. Hope you find something useful. http://stackoverflow.com/q/7774365/978992 – 1100110 Oct 18 '11 at 04:10
  • I am unsure what -march is supposed to do (optimization?) but I never used it myself. – he_the_great Oct 18 '11 at 14:39
-3

Digital Mars compilers and GCC compilers use different object file formats. Either use (gdc and gcc) or (dmd and dmc).

cyco130
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  • Can I work around this by putting it in a "formal" library, i.e. `libFoo.a`? – Maxpm Oct 17 '11 at 19:39
  • Not sure but I doubt it. But dynamically linked libraries (.dll, or .so) should probably work. – cyco130 Oct 17 '11 at 19:41
  • Unless I'm doing something wrong again, dynamic libraries don't work, either. Same error. – Maxpm Oct 17 '11 at 20:58
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    DMD only produces different formats on Windows. Archives are still the same format, shared I think just has additional requirements. – he_the_great Oct 17 '11 at 21:05