I am trying to call a D function from C. Here is the D code:

```
/* dcode.d */
extern (C) nothrow @nogc @system {
    double multNum(double x, double y)
    {
        return x*y;
    }
}
```

Then the C code:

```
/* ccode.c */
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>

extern double multNum(double x, double y);

int main()
{
    printf("output: %f", multNum(3.0, 4.0));
    return 0;
}

```

Then I compile with:

```
ldc2 -c dcode.d
gcc -c ccode.c
gcc -o output ccode.o dcode.o
```

I get the error:

```
dcode.o: In function `ldc.register_dso':
dcode.d:(.text.ldc.register_dso+0x6e): undefined reference to `_d_dso_registry'
collect2: error: ld returned 1 exit status
```

Compiler versions:

```
$ ldc2 --version
LDC - the LLVM D compiler (1.1.0):
  based on DMD v2.071.2 and LLVM 3.9.1
  built with LDC - the LLVM D compiler (1.1.0)
  Default target: x86_64-unknown-linux-gnu
  Host CPU: ivybridge
  http://dlang.org - http://wiki.dlang.org/LDC

  Registered Targets:
    x86    - 32-bit X86: Pentium-Pro and above
    x86-64 - 64-bit X86: EM64T and AMD64

```

```
$ gcc --version
gcc (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
```

I would appreciate it if someone could point out my mistake. Thank you in advance

On Thursday, 23 March 2017 at 09:11:28 UTC, data pulverizer wrote:
> I am trying to call a D function from C. Here is the D code:
>
> ```
> /* dcode.d */
> extern (C) nothrow @nogc @system {
>     double multNum(double x, double y)
>     {
>         return x*y;
>     }
> }
> ```
>
> [...]

It has to do with module references to druntime stuff. You can either try adding a

pragma(LDC_no_module_info); //I think it is spelled correctly.

or you can use ldc to link and it will link druntime

gcc ccode.c -c
ldc2 dcode.d code.o

I don't know how well that will work.

On Thursday, 23 March 2017 at 10:16:22 UTC, Nicholas Wilson wrote:
>
> It has to do with module references to druntime stuff. You can either try adding a
>
> pragma(LDC_no_module_info); //I think it is spelled correctly.
>
> or you can use ldc to link and it will link druntime
>
> gcc ccode.c -c
> ldc2 dcode.d code.o
>
> I don't know how well that will work.

Many thanks, I tried:

```
pragma(LDC_no_moduleinfo) // https://wiki.dlang.org/LDC-specific_language_changes#LDC_no_moduleinfo
```

which worked, your method of doing the final compilation using ldc2 (or dmd) also works :-)

Is there a dmd equivalent for `pragma(LDC_no_module_info);`? Attempting the final compilation `gcc -o output ccode.o dcode.o` after the second stage compilation `dmd -c dcode.d` gives an error:

```
dcode.o: In function `_D5dcode7__arrayZ':
dcode.d:(.text._D5dcode7__arrayZ+0x23): undefined reference to `_d_arraybounds'
dcode.o: In function `_D5dcode8__assertFiZv':
dcode.d:(.text._D5dcode8__assertFiZv+0x23): undefined reference to `_d_assert'
dcode.o: In function `_D5dcode15__unittest_failFiZv':
dcode.d:(.text._D5dcode15__unittest_failFiZv+0x23): undefined reference to `_d_unittest'
dcode.o:(.text.d_dso_init[.data.d_dso_rec]+0x22): undefined reference to `_d_dso_registry'
collect2: error: ld returned 1 exit status
```

```
dmd --version
DMD64 D Compiler v2.073.2
Copyright (c) 1999-2016 by Digital Mars written by Walter Bright
```

On Thursday, 23 March 2017 at 10:49:37 UTC, data pulverizer wrote:
> On Thursday, 23 March 2017 at 10:16:22 UTC, Nicholas Wilson wrote:
>>
>> It has to do with module references to druntime stuff. You can either try adding a
>>
>> pragma(LDC_no_module_info); //I think it is spelled correctly.
>>
>> or you can use ldc to link and it will link druntime
>>
>> gcc ccode.c -c
>> ldc2 dcode.d code.o
>>
>> I don't know how well that will work.
>
> Many thanks, I tried:
>
> ```
> pragma(LDC_no_moduleinfo) // https://wiki.dlang.org/LDC-specific_language_changes#LDC_no_moduleinfo
> ```
>
> which worked, your method of doing the final compilation using ldc2 (or dmd) also works :-)
>
> Is there a dmd equivalent for `pragma(LDC_no_module_info);`? Attempting the final compilation `gcc -o output ccode.o dcode.o` after the second stage compilation `dmd -c dcode.d` gives an error:
>
> ```
> dcode.o: In function `_D5dcode7__arrayZ':
> dcode.d:(.text._D5dcode7__arrayZ+0x23): undefined reference to `_d_arraybounds'
> dcode.o: In function `_D5dcode8__assertFiZv':
> dcode.d:(.text._D5dcode8__assertFiZv+0x23): undefined reference to `_d_assert'
> dcode.o: In function `_D5dcode15__unittest_failFiZv':
> dcode.d:(.text._D5dcode15__unittest_failFiZv+0x23): undefined reference to `_d_unittest'
> dcode.o:(.text.d_dso_init[.data.d_dso_rec]+0x22): undefined reference to `_d_dso_registry'
> collect2: error: ld returned 1 exit status
> ```
>
> ```
> dmd --version
> DMD64 D Compiler v2.073.2
> Copyright (c) 1999-2016 by Digital Mars written by Walter Bright
> ```

Those functions are the bounds checking function, the non unittest assert function, the unittest function an module initialisation function respectively. dmd -boundscheck=off -release should get rid of the first two, you didn't compile with -unittest so I'm not sure why the thord one is there at all. For _d_dso_registry all i can suggest is see what -betterC gets you.

On Thursday, 23 March 2017 at 11:32:25 UTC, Nicholas Wilson wrote:
> On Thursday, 23 March 2017 at 10:49:37 UTC, data pulverizer wrote:
>> On Thursday, 23 March 2017 at 10:16:22 UTC, Nicholas Wilson wrote:
>>>
>>> It has to do with module references to druntime stuff. You can either try adding a
>>>
>>> pragma(LDC_no_module_info); //I think it is spelled correctly.
>>>
>>> or you can use ldc to link and it will link druntime
>>>
>>> gcc ccode.c -c
>>> ldc2 dcode.d code.o
>>>
>>> I don't know how well that will work.
>>
>> Many thanks, I tried:
>>
>> ```
>> pragma(LDC_no_moduleinfo) // https://wiki.dlang.org/LDC-specific_language_changes#LDC_no_moduleinfo
>> ```
>>
>> which worked, your method of doing the final compilation using ldc2 (or dmd) also works :-)
>>
>> Is there a dmd equivalent for `pragma(LDC_no_module_info);`? Attempting the final compilation `gcc -o output ccode.o dcode.o` after the second stage compilation `dmd -c dcode.d` gives an error:
>>
>> ```
>> dcode.o: In function `_D5dcode7__arrayZ':
>> dcode.d:(.text._D5dcode7__arrayZ+0x23): undefined reference to `_d_arraybounds'
>> dcode.o: In function `_D5dcode8__assertFiZv':
>> dcode.d:(.text._D5dcode8__assertFiZv+0x23): undefined reference to `_d_assert'
>> dcode.o: In function `_D5dcode15__unittest_failFiZv':
>> dcode.d:(.text._D5dcode15__unittest_failFiZv+0x23): undefined reference to `_d_unittest'
>> dcode.o:(.text.d_dso_init[.data.d_dso_rec]+0x22): undefined reference to `_d_dso_registry'
>> collect2: error: ld returned 1 exit status
>> ```
>>
>> ```
>> dmd --version
>> DMD64 D Compiler v2.073.2
>> Copyright (c) 1999-2016 by Digital Mars written by Walter Bright
>> ```
>
> Those functions are the bounds checking function, the non unittest assert function, the unittest function an module initialisation function respectively. dmd -boundscheck=off -release should get rid of the first two, you didn't compile with -unittest so I'm not sure why the thord one is there at all. For _d_dso_registry all i can suggest is see what -betterC gets you.

I just compiled `dmd -c dcode.d -betterC -boundscheck=off` (-betterC probably makes -boundscheck=off irrelevant but I threw it in as a prayer) I am still getting:

```
dcode.o:(.text.d_dso_init[.data.d_dso_rec]+0x22): undefined reference to `_d_dso_registry'
collect2: error: ld returned 1 exit status
```

On Thursday, 23 March 2017 at 12:06:14 UTC, data pulverizer wrote:
> On Thursday, 23 March 2017 at 11:32:25 UTC, Nicholas Wilson wrote:
>> On Thursday, 23 March 2017 at 10:49:37 UTC, data pulverizer wrote:
>>> [...]
>>
>> Those functions are the bounds checking function, the non unittest assert function, the unittest function an module initialisation function respectively. dmd -boundscheck=off -release should get rid of the first two, you didn't compile with -unittest so I'm not sure why the thord one is there at all. For _d_dso_registry all i can suggest is see what -betterC gets you.
>
> I just compiled `dmd -c dcode.d -betterC -boundscheck=off` (-betterC probably makes -boundscheck=off irrelevant but I threw it in as a prayer) I am still getting:
>
> ```
> dcode.o:(.text.d_dso_init[.data.d_dso_rec]+0x22): undefined reference to `_d_dso_registry'
> collect2: error: ld returned 1 exit status
> ```

Getting dmd to do the linking should work.
You may wish to see what mir (github.com/libmir) does to build in it's "Better C" mode, so i'm sure it is possible, I just don't know the incantations, sorry. Perhaps someone else can help.

On 2017-03-23 13:26, Nicholas Wilson wrote:

> Getting dmd to do the linking should work.
> You may wish to see what mir (github.com/libmir) does to build in it's
> "Better C" mode, so i'm sure it is possible, I just don't know the
> incantations, sorry. Perhaps someone else can help.

As an ugly workaround, you can defined the "_d_dso_registry" symbol yourself. To be sure, it should match the signature in the runtime.

-- 
/Jacob Carlborg