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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