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|How to compile/link/run C++ code with the C++ interface (for GNU/Linux)?|
Well, this is actually quite easy, especially if you are used to the C interface. There are a few tricks though. In this HOWTO, we assume that you have never used the C interface, and that you are a beginner with the C++ interface.
For the developper, the C++ interface is merely one header:
SWI-cpp.h. Its location depends on your version and distribution. For example, on Fedora 21, 64-bits, I found it in /usr/lib64/swipl-6.4.1/. Note that depending on your distribution, you may need to install an additional package to have it. For example under Fedora,
swipl is provided by the package
pl but the header is provided by
swipl-ld will help you compile and link your code without having to worry for the location of library files, or the compilation options.
This file will help you to get the compilation options right.
Here is a real world Makefile. Note that I need to give
swipl-ld the option -ld g++ because otherwise it uses the C compiler which is unable to link with the C++ libraries.
CXXFLAGS=--std=c++11 CXXFLAGS+=$(shell pkg-config swipl --cflags) LD=swipl-ld LDFLAGS=--std=c++11 -shared -ld g++ SRC=$(wildcard *.cpp) OBJ=$(SRC:.cpp=.o) EXEC=interp.so DESTDIR=.. all : $(EXEC) $(EXEC) : $(OBJ) $(LD) $(LDFLAGS) -o $@ $^ mv $(EXEC) $(DESTDIR) database.o: database.cpp table.h table-kfdesc.h table-kprocs.h \ table-kfs.h update-add-entry.h update.h update-delete-entry.h filemode.h \ table-kmem.h database.h update-change-value.h # ... a lot more of dependencies specification here .PHONY : clean clean : rm -rf *.o mrproper : clean rm -f $(EXEC)
Indeed. You have to use load_foreign_library/1. For example, if your library is
libs/mylib.so, you have to do ?-
You have others, non-prolog, symbols that are still unresolved after loading the library in Prolog. You can remove the option -shared from
swipl-ld to see those. The linker will complain about the missing function
main (which is normal) and missing prolog symbols (which is normal). You can filter the output against the pattern "PL_" to get rid of the latter and see what are the others symbols that could not be resolved (which is NOT normal).