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Using libtool with other languages

Libtool was first implemented in order to add support for writing shared libraries in the C language. However, over time, libtool is being integrated with other languages, so that programmers are free to reap the benefits of shared libraries in their favorite programming language.

This chapter describes how libtool interacts with other languages, and what special considerations you need to make if you do not use C.

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:

  1. 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++ in order to protect users from conflicting implementations of features such as constructors, exception handling, and RTTI.
  2. 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.
  3. C++ compilers will link some Standard C++ library in by default, but libtool does not know which are these libraries, 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. However, running the C++ compiler directly may lead to problems related with inter-library dependencies.

The conclusion is that libtool is not ready for general use for C++ libraries. You should avoid any global or static variable initializations that would cause an "initializer element is not constant" error if you compiled them with a standard C compiler.

There are other ways of working around this problem, but they are beyond the scope of this manual.

Furthermore, you'd better find out, at configure time, what are the C++ Standard libraries that the C++ compiler will link in by default, and explicitly list them in the link command line. Hopefully, in the future, libtool will be able to do this job by itself.

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