There needs to be a referance to library from main in
order for the libray to be included.
Mickey
--- David Fleury <[EMAIL PROTECTED]>
wrote:
> Hi,
>
> I want a library (libdata.a) with a static bool
> initialized only to call
> a function "Function"
>
> So, I create a library (using ar) and link with an
> empty main
>
> (make; make main)
>
> When I launch ./test_data nothing happen
>
>
>
> But if I link main.cpp and data.o directly (make
> main_a) and launch
> ./test_data,
>
> I have got "Calling Function" has expected.
>
>
>
> So, what is the difference between linking with a .a
> and a .o ?
>
> I though that *.a was only a set of .o and there
> were no difference for
> the link. (Clearly I am wrong).
>
> And How do I force the wanted effect using a library
> ?
>
> (The goal is to have a static library with a factory
> where each Concrete
> object register
>
> Itself to the factory using a initialized bool - cf
> Modern C++ Design
> c.8 )
>
>
>
> Here my samples with two files and a makefile
>
>
>
> // BEGIN data.cpp
>
> #include <iostream>
>
> bool Function() { return std::cout << "Calling
> Function" << std::endl;
> }
>
> namespace { bool staticCall = Function(); }
>
> // END data.cpp
>
>
>
> // BEGIN main.cpp
>
> Int main() {}
>
> // END main.cpp
>
>
>
>
>
> # BEGIN Makefile
>
> libdata.a:data.o
>
> ar -r $@ $^
>
>
>
> main:libdata.a
>
> g++ -o test_data main.cpp -L. -ldata
>
>
>
> main_a:
>
> g++ -o test_data main.cpp data.o
>
>
>
> .cpp.o:
>
> g++ -c -o $@ $<
>
> #END Makefile
>
>
>
>
>
> Thanks for your help,
>
> David
>
>
>
>
>
>
>
>
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