This example shows an example of fail of using a C function in a .a archive with ctypes with the gcc toolchain.
a.c exposes a f function. The Makefile compiles it into a a.o object and packages it in a libtest.a archive.
The main.ml file tries to call this function with the Ctype module. It fails beacause Ctypes uses a dynamic link and
the gcc toolchain only extracts from the libtest.a archives the object files which are statically linked.
The error is:
$ dune exec ./main.exe
Done: 100% (2/2, 0 left) (jobs: 0)Fatal error: exception Dl.DL_error("_build/default/main.exe: undefined symbol: f")