Re: Thread-safety, lex and yacc.

Nicholas Dronen <ndronen@io.frii.com> wrote:


: Does anyone have experience with making an apparantly non-thread-safe
: lex/yacc code base thread-safe? Suggestions and pointers welcome.


: [If you tell flex to generate a C++ lexer, it's thread safe. Haven't
: seen a thread-safe yacc but I haven't looked very hard either. It
: wouldn't be hard to do. -John]


Flex C lexers are not thread safe, but I recently wrote an awk script
to make one thread safe. (C++ could not be used.)


Basic approach:
Redefine all globals in a structure passed in via YY_DECL.
The awk script removes the global definitions, substitutes
arg->global for all globals, and changes the generated
subroutines to take that structure also.


The script also dumped the definition of yy_buffer_state to
a header file so the argument structure could reference it.


A *lot* of the generated subroutines were superfluous for my
intended use, so the awk script just removed those. I also
created an error return for yy_get_next_buffer() and took out
the exit() call.


-troy

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