🚀 go-pugleaf

"@please@no.spam" <""ddrav\"@please@no.spam"> writes:

> Now I'm trying to add a program written in C++ to the suite. I find
> that if I compile libutil.a with gcc the C++ program can't link with
> it (unresolved references) and if I compile it with g++ the C
> programs can't use it. Do I need to keep two versions around or is
> there some magic switch I'm missing?

This is a pure C++ question.  You should put 

#ifdef __cplusplus
extern "C" {
#endif

...
#ifdef __cplusplus
}
#endif

around your header.  After this you should be able to compile the
library with the C compiler and link it to C++ programs (always using
the C++ compiler to do the link).

Without the extern "C" stuff, C++ compiler "mangles" the function
names (for several raisons, most notable beeing: preventing linking
code compiled using different ABI and beeing able to do overloading).

Yours,

-- 
Jean-Marc

The problem is that you have to put on the header files of your library
the following code before and after the declarations of the functions and
structures:

#ifdef __cplusplus
extern "C"{
#endif

// Declarations of the functions and structures

void f();
void g();


#ifdef _cplusplus
}
#endif

In that way the g++ compiler will known that you are using some C code and
the undefined references will not occour again.


[]' s
Andre Paim Lemos
CS Student - UFMG - Brazil

On Tue, 19 Nov 2002, @please@no.spam wrote:

> My question relates to the complexities of cross-linking object files 
> and libraries between C and C++ (specifically gcc and g++) compiled code.
> 
> Details: I'm developing a suite of Unix applications. Each app uses at 
> least one shared library and at least one executable which links to it. 
> I've also got a collection of utility routines in C which are used by 
> the entire suite, including the shared libraries.
> 
> What I've been doing, and which works quite well, is to compile the 
> utility routines into a little static library (libutil.a), making sure 
> to compile with -fpic. This way executables can link to it statically, 
> which I prefer for simplicity of delivery, and the shared libraries can 
> do the same, in which case these symbols become part of the shlib. In 
> the latter case I make the utility symbols private to the shlib with a 
> version script.
> 
> Now I'm trying to add a program written in C++ to the suite. I find that 
> if I compile libutil.a with gcc the C++ program can't link with it 
> (unresolved references) and if I compile it with g++ the C programs 
> can't use it. Do I need to keep two versions around or is there some 
> magic switch I'm missing?
> 
> Thanks in advance
> DD
> 
> 

Jean-Marc Bourguet wrote:
> "@please@no.spam" <""ddrav\"@please@no.spam"> writes:
> 
> 
>>Now I'm trying to add a program written in C++ to the suite. I find
>>that if I compile libutil.a with gcc the C++ program can't link with
>>it (unresolved references) and if I compile it with g++ the C
>>programs can't use it. Do I need to keep two versions around or is
>>there some magic switch I'm missing?
> 
> 
> This is a pure C++ question.  You should put 
> 
> #ifdef __cplusplus
> extern "C" {
> #endif

Oh, I should have known that (and did in some dark corner of my brain). 
Thanks and sorry for the dumb question.

DD