Is it possible to load a function symbol from an executable

To allow foo.out to be used as both an executable and as a library, you first need to compile it with -FPIE and -pie to allow it to be read via dlopen as well as -rdynamic to export the symbols it contains:

gcc -fPIE -pie -rdynamic foo.c -o foo.out

Then update bar.c to use dlopen and dlsym:

#include 
#include 
int main() {
    void lib = dlopen("./foo.out",RTLD_LAZY);
    if (!lib) {
        printf("dlopen failed: %s\n", dlerror());
        return 1;
    }
    int (Main)(int) = dlsym(lib,"Main");
    if (!Main) {
        printf("dlsym failed: %s\n", dlerror());
        return 1;
    }
    return Main(2);
}

And link with libdl:

gcc bar.c  -o bar.out -ldl

Then you'll get the expected results:

[dbush@db-centos7 ~]$ ./bar.out
A2B[dbush@db-centos7 ~]$