Using C++ with VxWorks

	Using the GNU g++ compiler to develop C++ code for VxWorks is
really quite simple. The most difficult part is building the compiler
and support tools. Once this is done developing C++ code for VxWorks
is a snap. The following is how we use g++ tools on our Suns for 68k
targets. Please note that this has been tested only on the following
systems:
	
	Solaris 2.3/2.4

and tested only on the following targets:

	Tadpole TP41V, Motorola MVME-167 & MVME-133A running VxWorks
5.2.

The big change:
---------------

	Previous versions of libg++ where made such that all needed
items were in libg++.a. Starting with version 2.7.0 the functions that
are part of the C++ standard library are in libstdc++. You will have
to add/change link lines!

Building the cross development tools:
-------------------------------------
	Obtain gcc-2.7.x. (Note: we are currently running gcc-2.7.0 &
			   libg++-2.7.0) 

	First, untar everything. Move into the gcc directory. 

	Now, the first thing to do is to build gcc for your host.
Follow the installation instructions. Make sure to read the INSTALL
file, particularly the sections on building cross compilers. 

	Run configure using --target=m68k-wrs-vxworks (or whatever).

This way you can have your other crosstools named consistently with
gcc.

	We found that the following changes to the generated makefile
are useful: 

	1> Change CFLAGS to -O2 & BOOT_CFLAGS to $(CFLAGS).
	2> Change GCC_FOR_TARGET to ./xgcc -B./ -I/vx/h.
	3> Remove -g1 from LIBGCC2_CFLAGS.
	4> Add -I/vx/h -DVXWORKS to the GCC_FOR_TARGET definition for
	   compiling libobjc.a.

	Run make and install. 

Building  libg++/stdc++ for VxWorks:
--------------------------------------
	1> Obtain libg++ and unpack it.
	2> Move into the directory libg++-2.x.x.
	3> Get the patch file libg++-2.7.x. 
	4> Run configure: "./configure --host=your_host_type
           --target=m68k-wrs-vxworks".
	4> Apply the patch file. You may have to apply the base level
	   Makefile patches by hand.

	5> Run make.
	
VxWorks and g++:
----------------
	To call a routine compiled under g++ you must turn off name
mangling for that routine:

extern "C" {
void myRoutine(int);
};

	To use any globally declared objects (including cin, cout,
cerr), you can do the following:

	1> Before you access any of the global objects, call
	   __do_global_ctors():

extern "C" {
    void __do_global_ctors();
....

void mystart()
{
  __do_global_ctors();
....

	2> Link your object files using the -Ur option of the GNU
	   linker:

		'whatever_you_called_it' -Ur -X -o xx.o yy.o ... \
		-L/zzz -lg++ -libstdc++ -libgcc

	All in all quite simple. The VxWorks archive has several C++
classes already. Some files of interest are:

flags_class.shar
msgque_class.shar
pipe.shar
task_class.shar
wdog_class

Richard Neitzel thor@atd.ucar.edu	     	Torren med sitt skjegg
National Center For Atmospheric Research	lokkar borni under sole-vegg
Box 3000 Boulder, CO 80307-3000			Gjø'i med sitt shinn
303-497-2057					jagar borni inn.