Re: Error: undefined reference to

[Guy Harrison]

Ben Rennigen wrote:

> Hi,
> 
> "Guy Harrison" <swamp-DEL-dog@ntlworld.com> schrieb im Newsbeitrag
> news:0k3cmc.ebj1.ln@sd-if.swampdog...
> 
>> ...but not supplied the code body (definition). This may be because
>> you've not written it at all or because you've not passed the
>> object-file/lib containing the definition to the linker.
> 
> this may be the error - I compile the code with:
> 
> "g++ prog_complex.cpp -o prog_complex"
> 
> So there are no information about any object file or lib. I think my
> compile - commandline isn't correct, how can I tell the compiler/linker to
> link the object file of the file containing my complex-class
> implementation?

$ g++ -o prog_complex prog_complex.cpp foo.o

...assuming foo.cpp having been subject to

$ g++ -c foo.cpp

If you've built a library then (eg: man, search for '-L' and '-l') "-L.
-lfoo" would be in order (for libfoo.* - eg: libfoo.so/libfoo.a).

Fwiw...

$ g++ -o prog_complex prog_complex.cpp foo.cpp

...will work. Obviously the compiler is possibly being made to recompile
when it may not ought (hint: "man [g]make" and gcc -M? option).