Re: Is YACC / PCCTS used in commercial compilers?

johnr@ims.com (John Roberts) wrote:
>>> I'm wondering if commercial compilers like Microsoft Visual C++,
>>> Borland C++, Sun SparcWorks C / C++ use tools like YACC or PCCTS to
>>> handle parsing.
..
>What I'm trying to understand is:
>
> 1) What are the problems using YACC/PCCTS in commercial compilers?
> (i.e. why aren't they used?)
>
> 2) What techniques are used in place of YACC/PCCTS for commerical
> compiler parsing?
>
>Ideas, anyone?


When I worked at Digital several of the compilers used a tool *like*
YACC and others used one *like* PCCTS. I believe the YACC like tool
was called LALRPAT and I can't remember the name of the other one.


Historically the best reason for not using YACC was that its tables
take up a lot of memory to implement a real programming language. This
probably ruled out its use in all PeeCee compilers. Now that Bill has
graced use with 32 bits this is very little of an issue. However,
compiler vendors are not going to go back and rewrite their working
code just to use a tool.


Another reason that compilers may not be designed with YACC is speed.


Finally YACC's error recovery and diagnostics is simply terrrible.


John
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