flex error "start-condition stack underflow" with "%option full" on parsing files with chinese character -

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i have flex scanner run correctly long time, on files chinese characters. want make faster, , add "%option full", indeed 3x faster. may fail on files comments contain chinese characters.

the error message "start-condition stack underflow".

i add printing statement lex source code, , find scanner print error in start condiiton sc, have not run code segment contain "yy_push_state(sc)". think there may overflow in flex buffer.

so do?

for historical reasons (or something), if use %option full or %option fast, flex default producing 7-bit scanner (i.e. %option 7bit).

that's unsafe, since 7-bit scanner not attempt verify scanned text consists of 7-bit ("ascii") characters, , behaviour in case encounters character high-order bit set undefined. happen if input utf-8 or multibyte.

so need specify %option 8bit full. increase size of scanner tables, these days might not matter much. might want try %option 8bit full ecs intermediate setting. (i'm pretty sure 8bit not necessary ecs, can't hurt.)


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