Help learning how to interface with c(++)

[Kai Meyer]

On 03/07/2011 08:57 AM, Kai Meyer wrote:
> On 03/05/2011 06:24 AM, Kagamin wrote:
>> Kai Meyer Wrote:
>>
>>> I can't seem to get this to work right:
>>>
>>> gcc -m32 -shared -fPIC Test.cpp -o libTest.so
>>> g++ -m32 test_c.cpp -L. -lTest -o test_c
>>> wine htod.exe Test.h Test.d
>>> dmd test_d.d Test.d -L-L. -L-lTest -oftest_d
>>> test_d.o: In function `_Dmain':
>>> Test.d:(.text._Dmain+0x20): undefined reference to `increment'
>>> collect2: ld returned 1 exit status
>>> --- errorlevel 1
>>> make: *** [test_d] Error 1
>>>
>>> The resulting test_c binary from g++ works as intented (With either
>>> LD_LIBRARY_PATH="." or LD_RUN_PATH="."):
>>> $ ./test_c
>>> Count = 0
>>> Count = 1
>>> $ ldd test_c
>>> linux-gate.so.1 => (0x00ad1000)
>>> libTest.so (0x005b9000)
>>
>> try non-shared libTest, dmd prefers single executable compilations.
>
> Is that the only option? I know it's possible to link to external c
> libraries, and I'd like to learn how.

So I monkeyed around a little bit, and found out that if I change 
"extern (C)" to "extern (C++)", the library links correctly and the 
program runs.

That lead me to believe that if I added the "-cpp" option to htod.exe, 
it would generate extern(C++) functions. But I got a blank Test.d file 
doing it that way.

So, gcc created a libTest.so with a function in it, and dmd only finds 
the function with extern(C++) and not with extern(C).

Now I'm just confused, yet pleased something worked.

-Kai Meyer