David A. Wheeler wrote: > On 11/9/06, Crispin Cowan <[EMAIL PROTECTED]> wrote: > >>> Prior to Java, resorting to compiling to byte code (e.g. P-code back in >>> the Pascal days) was considered a lame kludge because the language >>> developers couldn't be bothered to write a real compiler. >>> > I believe that is completely and totally false. > If you want to claim p-code itself was lame, fine. > But let's keep the history accurate. > > The UCSD p-system was created in the late 1970's SPECIFICALLY for > PORTABILITY of executable code: You could ship p-code to any > machine, and it would run. That is not inconsistent with my claim. The "P-code is a kludge to get around writing a real compiler" is multiplied by the diversity of architectures. Writing a native code generator is a cost you pay for every supported architecture. So in more detail, P-code is a performance-compromising kludge to avoid having to write a *lot* of real code generators.
One major change between then and now is consolidation of CPUs. Then, there really was a very broad diversity of CPU architectures (IBM mainframe, IBM AS/400, DEC VAX, PDP, DEC10, DEC20, Data General, Apollo, HP, Xerox Sigma, x86, 68000, NS32K, etc. etc.) and they all more or less mattered. It is *very* different today: the list of CPU architectures that matter is much shorter (x86, x86-64, SPARC, POWER, Itanium): only 4 instead of a baker's dozen, and of those 4, a single one (x86) is a huge majority of the market. Pascal was a student language, not often used for commercial development, so money for Pascal development was scarce. In contrast, real languages for commercial purposes (PL/1, COBOL, FORTRAN, C) all used native code generators. P-code was precisely a performance-compromising kludge to allow Pascal to be portable with less development effort. Of course, there was one big exception: Turbo Pascal. Arguably the most popular Pascal implementation ever. And it used a native code generator. The need for portability, and the cost of portability (how many platforms you really have to port to) has dropped dramatically. Bytecode should be going away, the the architectural mistake of Java and C#/.Net are going to preserve it for some time to come :( Crispin -- Crispin Cowan, Ph.D. http://crispincowan.com/~crispin/ Director of Software Engineering, Novell http://novell.com Hack: adroit engineering solution to an unanticipated problem Hacker: one who is adroit at pounding round pegs into square holes _______________________________________________ Secure Coding mailing list (SC-L) [email protected] List information, subscriptions, etc - http://krvw.com/mailman/listinfo/sc-l List charter available at - http://www.securecoding.org/list/charter.php
