A quick search for "reentrant flex bison" gets me this: https://stanislaw.github.io/2016/03/29/reentrant-parser-using-flex-and-bison.html https://stanislaw.git

A quick search for "reentrant flex bison" gets me this: https://stanislaw.github.io/2016/03/29/reentrant-parser-using-flex-and-bison.html https://stanislaw.github.io/2016/03/29/reentrant-parser-usin... which in turn links this: https://github.com/blynn/symple/tree/75aaea79141a18a234c94dc8a2a7277d42fe83aa https://github.com/blynn/symple/tree/75aaea79141a18a234c94dc... The magic flags are: %option reentrant and %lex-param { yyscan_t scanner } %parse-param { yyscan_t scanner } %parse-param { val_callback_t callback } ... so ... it seems a reentrant flex/bison parser is easily possible?