bar.cpp

#include <iostream>
#include <uuid/uuid.h>

extern "C" int foo(int x);

int main(int argc, char *argv[])
{
    auto total = foo(argc) + foo(argc);
    uuid_t u;
    uuid_generate(u);

    char uuid_text[37];
    uuid_unparse(u, uuid_text);

    std::cout << "UUID: " << uuid_text << "\n";

    return total;
}

foo.c

int foo(int x)
{
    return x+x;
}

Makefile

all: foo

CXXFLAGS+= -std=c++11 -Wall
LDLIBS+=-lstdc++ $(shell pkg-config --libs uuid)

foo: foo.o bar.o

.PHONY: clean all

clean:
        $(RM) foo foo.o bar.o

sample_run.txt

$ make clean
rm -f foo foo.o bar.o
$ make CXX=clang++ && ./foo ; echo $?
cc    -c -o foo.o foo.c
clang++ -std=c++11 -Wall   -c -o bar.o bar.cpp
cc   foo.o bar.o  -lstdc++ -luuid   -o foo
UUID: e55e3138-5634-4852-87fd-ab993d2a95d1
4