Examples

This section contains two examples of dynamic programs. In all these examples, it is assumed that a standard development environment has been set up: system build tree, search path, boot and initialization of target machine. It also assumes that the chorus_root_directory is the path of the target root directory on the NFS host (for example /home/chorus/root), the name of the target is jericho, and the environment variable WORK refers to the directory used for building these examples

Dynamic Link at Actor Start-up

The following dynamic program uses a custom dynamic library which will be loaded and linked at actor start-up. It uses a function foo() which is defined in the dynamic library. This function calls a function bar() defined in the main program.

This is the dynamic program progdyn.c:

#include <chorus.h> 

extern void foo();

main() {
    foo();              /* calling foo defined in the library */
}

void bar() {
    printf ("bar called\n");
}

This is the dynamic library libdyn.c:

#include <chorus.h> 

extern void bar();

void foo() {
    printf ("Calling bar\n");
    bar();              /* calling bar defined in the main program */
}

Building the Dynamic Library

Create a directory libdyndir in $WORK, containing libdyn.c and the following Imakefile:

SRCS = libdyn.c
DynamicLibraryTarget (libdyn.so, libdyn.o, , , ,-Xlinker -soname=libdyn.so )
Depend(libdyn.c)

In the libdyndir directory, build the dynamic library libdyn.so using the ChorusOSMkMf, make depend, and make commands.

Building the Dynamic Program

Create a directory progdyndir in $WORK, containing progdyn.c and the following Imakefile:

SRCS = progdyn.c
DynamicUserTarget (progdyn, progdyn.o, , 
        $(WORK)/libdyndir/libdyn.so,
        $(WORK)/libdyndir/libdyn.so, )
Depend()

In the progdyndir directory, build the dynamic program progdyn using the ChorusOSMkMf, make depend and make commands.

% ChorusOSMkMf $WORK
% make depend
% make

Running the Dynamic Program

Copy the dynamic program into the /bin subdirectory of the chorus_root_directory directory:

% cp $WORK/progdyndir/progdyn chorus_root_directory/bin 

Copy the dynamic library into the /lib subdirectory of the chorus_root_directory directory:

% cp $WORK/libdyndir/libdyn.so chorus_root_directory/lib 

Then, the following command will tell the runtime linker where to find the libdyn.so dynamic library:

% rsh jericho setenv LD_LIBRARY_PATH /lib 

Alternatively, set the runpath to /lib in the ldopts argument of the program macro (-rpath /lib).

Finally, the following command will start the program and dynamically load the libdyn.so library:

% rsh jericho arun /bin/progdyn

Explicit Link Using dlopen

The following program explicitly loads a dynamic library at runtime, using the function dlopen(). It searches for the address of the dynfunc() function defined in the library and calls this function.

This is the dynamic program progdyn2.c:

#include <chorus.h>
#include <cx/dlfcn.h>

int main()
{
    void    (*funcptr)();       /* pointer to function to search */
    void    *handle;            /* handle to the dynamic library */

        /* finding the library */
    handle = dlopen ("libdyn2.so", RTLD_NOW);
    if !(handle) { printf ("Cannot find library libdyn2.so\n"); exit(1); } 

        /* finding the function in the library */
    funcptr = (void (*)()) dlsym (handle, "dynfunc");
    if !(funcptr) { printf ("Cannot find function dynfunc\n"); exit(1); }

        /* calling library function */
    (*funcptr)();
}

This is the dynamic library libdyn2.c:

#include <chorus.h> 

void dynfunc() {
    printf ("Calling dynfunc\n");
}

Building the Program and the Library

The program and library above are built in the same way as in the previous example, using two Imakefiles:

Create a directory libdyn2dir in $WORK, containing libdyn2.c and the following Imakefile:

SRCS = libdyn2.c
DynamicLibraryTarget (libdyn2.so, libdyn2.o, , , , )
DependTarget(libdyn2.c)

Create a directory progdyn2dir in $WORK, containing progdyn2.c and the following Imakefile:

SRCS = progdyn2.c
DynamicUserTarget (progdyn2, progdyn2.o, , , , )
Depend(progdyn2.c)

Running the Dynamic Program

Copy the dynamic program into the /bin subdirectory of the chorus_root_directory directory:

% cp $WORK/progdyn2dir/progdyn2 chorus_root_directory/bin 

Copy the dynamic library into the /lib subdirectory of the chorus_root_directory directory:

% cp $WORK/libdyn2dir/libdyn2.so chorus_root_directory/lib 

Then, the following command will tell the runtime linker where to find the libdyn2.so dynamic library:

% rsh jericho setenv LD_LIBRARY_PATH /lib

Finally, the following command will start the program:

% rsh jericho arun /bin/progdyn2 

At program start-up, the runtime linker will only load the executable progdyn2. The libdyn2.so library will be loaded when the dlopen() function is called.