6.1 Writing libraries for C++ ¶
Creating libraries of C++ code should be a fairly straightforward
process, because its object files differ from C ones in only three ways:
- Because of name mangling, C++ libraries are only usable by the C++
compiler that created them. This decision was made by the designers of
C++ to protect users from conflicting implementations of
features such as constructors, exception handling, and RTTI.
- On some systems, the C++ compiler must take special actions for the
dynamic linker to run dynamic (i.e., run-time) initializers. This means
that we should not call
ld directly to link such libraries, and
we should use the C++ compiler instead.
- C++ compilers will link some Standard C++ library in by default, but
libtool does not know what these libraries are, so it cannot even run
the inter-library dependence analyzer to check how to link it in.
Therefore, running
ld to link a C++ program or library is deemed
to fail.
Because of these three issues, Libtool has been designed to always use
the C++ compiler to compile and link C++ programs and libraries. In
some instances the main() function of a program must also be
compiled with the C++ compiler for static C++ objects to be properly
initialized.