5 May 1991
Geoffrey Furnish

This directory contains my files for the OS/2 port of PLPLOT.

There were a number of things which had to be dealt with in order to
get PLPLOT to work correctly on OS/2.

The biggest problem was that PLPLOT had apparently been developed on
machine(s) with hardware architecture(s) differing significantly from
the architecture of the Intel family.  Although there are certainly
good reasons for the architectual choices made by other processor
vendors, PLPLOT was pretty blind in its reliance upon such
things. Further, PLPLOT was written entirely in K&R C, which is a
nightmare for Intel family processors.

In the process of bringing up PLPLOT on OS/2, I was driven to install
ANSI prototypes in a large number of the functions. Specifically, all
those taking float's as arguments (but not those taking float *) had
to be explicitly prototyped.  Note: the problem is not solved in the
prototype, however, unless the function actually uses an ANSI sytle
declaration.  So when I say I prototyped these functions, what I
really mean is that I declared the functions using ANSI syntax.
However, since there are still a fair number of compilers which do not
support ANSI style function declarations (SUN C for one--can you even
believe it???) I was not willing to force the conversion. Rather, I
made the declarations dependent upon a macro, PLSTDC.  Since I am not
aware of any compilers remaining in the OS/2 market which are not
ANSI, this is the default on OS/2.

Furthermore, there were several bugs in the inards of PLPLOT, where
surprising assumptions were made about machine architecture.  In one
routine, I discovered the amusing assumption that short == long !
That is of course patently false on Intel machines, so this had to be
"adjusted".  That was in plfill.c.

Another problem with this port was that sscanf breaks if linked with
the fortran stubs, and generates a null pointer assignment problem.
My only recourse in this case has been to remove sscanf, and replace
it with atol, or other functional equivalents, as the case allows.
This mostly affects the drivers, but some other files too.

Also, it should be noted that the OS/2 Fortran stubs were written for
use with Microsft Fortran. There are particular difficulties wtih MS
Fortran in regard to strings, so these stubs may or may not work with
other compilers.

To the best of my knowledge, all the changes I made consisted of
legitimate enhancements only, and no actual changes to functionality,
calling syntax, or internal algorithms.

Finally, I added a PLPLOT meta file writer, and a corresponding
renderer.

Enjoy.	Report problems to:
		furnish@dino.ph.utexas.edu