Hi, I've got this project that requires me to link into a C++
backend. It works just fine when using GDC:

gdc *.d [client libraries]

However, this command using DMD does not work:

dmd -L-lstdc++ *.d [client libraries]

I still get errors involving the standard library not being added
like:

/usr/include/c++/4.8/iostream:74: undefine reference to
`std::ios_base::Init::Init()'
(etc.)

What do I need to do to make this work? Thanks.

On Thursday, 16 April 2015 at 08:51:15 UTC, TheGag96 wrote:
> Hi, I've got this project that requires me to link into a C++
> backend. It works just fine when using GDC:
>
> gdc *.d [client libraries]
>
> However, this command using DMD does not work:
>
> dmd -L-lstdc++ *.d [client libraries]
>
> I still get errors involving the standard library not being added
> like:
>
> /usr/include/c++/4.8/iostream:74: undefine reference to
> `std::ios_base::Init::Init()'
> (etc.)
>
> What do I need to do to make this work? Thanks.

Can't get to linux machine now, but you can try place -L-lstdc++
after source files.

On Thursday, 16 April 2015 at 08:51:15 UTC, TheGag96 wrote:
> Hi, I've got this project that requires me to link into a C++
> backend. It works just fine when using GDC:
>
> gdc *.d [client libraries]
>
> However, this command using DMD does not work:
>
> dmd -L-lstdc++ *.d [client libraries]
>
> I still get errors involving the standard library not being added
> like:
>
> /usr/include/c++/4.8/iostream:74: undefine reference to
> `std::ios_base::Init::Init()'
> (etc.)
>
> What do I need to do to make this work? Thanks.

I don't know why that's happening, but you can explicitly link using gcc (or ld/gold directly) if you need to. E.g.

dmd -c myFile.d
gcc myFile.o -lphobos2

or whatever is necessary on your project/system.

On Thursday, 16 April 2015 at 08:51:15 UTC, TheGag96 wrote:
> Hi, I've got this project that requires me to link into a C++
> backend. It works just fine when using GDC:
>
> gdc *.d [client libraries]
>
> However, this command using DMD does not work:
>
> dmd -L-lstdc++ *.d [client libraries]
>
> I still get errors involving the standard library not being added
> like:
>
> /usr/include/c++/4.8/iostream:74: undefine reference to
> `std::ios_base::Init::Init()'
> (etc.)
>
> What do I need to do to make this work? Thanks.

Simple issue but unpleasant fix. You always must use C++ library that matches base C++ compiler. For GDC it is GCC (which is used by default). For DMD it is DMC (Digital Mars C compiler). For LDC it is whatever Clang standard library is called. All those are incompatible because rely on different compiler built-ins.

On 2015-04-16 11:56, Dicebot wrote:

> Simple issue but unpleasant fix. You always must use C++ library that
> matches base C++ compiler. For GDC it is GCC (which is used by default).
> For DMD it is DMC (Digital Mars C compiler). For LDC it is whatever
> Clang standard library is called. All those are incompatible because
> rely on different compiler built-ins.

The title says (Linux), where DMD uses GCC and not DMC.

-- 
/Jacob Carlborg

On 4/16/15 4:51 AM, TheGag96 wrote:
> Hi, I've got this project that requires me to link into a C++
> backend. It works just fine when using GDC:
>
> gdc *.d [client libraries]
>
> However, this command using DMD does not work:
>
> dmd -L-lstdc++ *.d [client libraries]
>
> I still get errors involving the standard library not being added
> like:
>
> /usr/include/c++/4.8/iostream:74: undefine reference to
> `std::ios_base::Init::Init()'
> (etc.)

Try dmd -v to tell you exactly what command it is running for link. Then play around with the link line to see if you can figure out a way to link it correctly.

We can work on fixing the situation from there. Maybe there's a way to link using dmd, maybe we have to fix dmd so it allows the correct link call.

-Steve

On Thursday, 16 April 2015 at 09:46:40 UTC, John Colvin wrote:
> On Thursday, 16 April 2015 at 08:51:15 UTC, TheGag96 wrote:
>> Hi, I've got this project that requires me to link into a C++
>> backend. It works just fine when using GDC:
>>
>> gdc *.d [client libraries]
>>
>> However, this command using DMD does not work:
>>
>> dmd -L-lstdc++ *.d [client libraries]
>>
>> I still get errors involving the standard library not being added
>> like:
>>
>> /usr/include/c++/4.8/iostream:74: undefine reference to
>> `std::ios_base::Init::Init()'
>> (etc.)
>>
>> What do I need to do to make this work? Thanks.
>
> I don't know why that's happening, but you can explicitly link using gcc (or ld/gold directly) if you need to. E.g.
>
> dmd -c myFile.d
> gcc myFile.o -lphobos2
>
> or whatever is necessary on your project/system.

I had wanted to try this too, but I wasn't sure if the linker knew where phobos2 was on my system. I just tried this now for funsies:

dmd -c *.d
g++ main.o [client files] -lphobos2

With or without that -lphobos2 flag, I get errors like these:

main.d(.text._Dmain+0x18e): undefined reference to `D3std5stdio16__T7writeln(TAyaZ7writeFAyaZv'

On Thursday, 16 April 2015 at 12:57:12 UTC, Steven Schveighoffer wrote:
>> /usr/include/c++/4.8/iostream:74: undefine reference to
>> `std::ios_base::Init::Init()'
>> (etc.)
>
> Try dmd -v to tell you exactly what command it is running for link. Then play around with the link line to see if you can figure out a way to link it correctly.
>
> We can work on fixing the situation from there. Maybe there's a way to link using dmd, maybe we have to fix dmd so it allows the correct link call.
>
> -Steve

Got it!! This is what helped me the most. I compiled a regular C++ program with the -v flag, found where my libstdc++.a was, added it to the command and bam. I really should have thought of this one earlier... Thanks for the quick support, everyone!

On Thursday, 16 April 2015 at 12:39:07 UTC, Jacob Carlborg wrote:
> On 2015-04-16 11:56, Dicebot wrote:
>
>> Simple issue but unpleasant fix. You always must use C++ library that
>> matches base C++ compiler. For GDC it is GCC (which is used by default).
>> For DMD it is DMC (Digital Mars C compiler). For LDC it is whatever
>> Clang standard library is called. All those are incompatible because
>> rely on different compiler built-ins.
>
> The title says (Linux), where DMD uses GCC and not DMC.

Does DMD also use GCC conventions on Linux when compiling extern(C++) code? I didn't know that.

On 2015-04-17 10:16, Dicebot wrote:

> Does DMD also use GCC conventions on Linux when compiling extern(C++)
> code? I didn't know that.

Not exactly sure that you mean by "conventions" but "extern(C++)" and "extern(C)" follows the ABI of the system compiler. On Linux that is GCC, on OS X it's Clang/GCC, on Windows it's either DMC or VS depending on what object format is used, I guess.

DMC is not even available for any other platform than Windows.

-- 
/Jacob Carlborg