Slow compilation of bison and lex grammar

Question

I used bison and flex for generating a C parser using a grammar.y file. It compiles properly and so fast in about 10 seconds. I have changed my bison and flex arguments in order to get C++ output, although it generate correct results but it take about 1 minute to compile and output CPP result of grammar. Does anyone have any idea for solving this problem? The grammar file is about 6000 lines.

Answer 1

It is quite common to have C++ compilation run slow as molasses, depending on the complexity of the C++ code. The C++ compiler has a lot of work to do, to figure things out. Much work more than a C compiler has to do. I have some C++ code that takes several minutes, and close to a gig of RAM, to chew through.

With a robo-generated LALR(1) parser that bison spews out from a 6000-line ruleset, that's not entirely an unexpected result. You could probably speed things up by dropping the -O optimization options, for the robo-generated grammar file, if the runtime performance from the parser is not critical. That will probably speed things up a bit.

You could also try updating your compiler. gcc has improved its performance noticeably, in recent releases, so if you're using an older gcc, you might see an improvement.

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