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Using reflex instead of flex in aprepro_lib

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Greg Sjaardema edited this page Oct 18, 2023 · 5 revisions

Steps needed to use reflex instead of flex... Note that there is additional work required to get the Scanner class working. This just gets you some of the way:

  • Delete FlexLexer.h
  • In aprepro_parser.h: -- Add #include "aprepro_parser.h" -- Change include of FlexLexer.h to reflex/flexlexer.h -- the int arguments on LexerOutput and LexerInput are size_t

In aprepro.ll:

  • Rename echo to do_echo

  • Add #undef yyterminate before #define yyterminate()

  • Add #undef YY_USER_ACTION before the #define YY_USER_ACTION

  • Add:

%option namespace=SEAMS
%option lexer=SEAMSFlexLexer
%option lex=yylex

In the /*** Flex Declarations and Options ***/ section.

  • Change %START to %s

  • All matching rules need to have the leading whitespace removed... For example,

 <VERBATIM>{
  "{VERBATIM(OFF)}" { BEGIN(INITIAL);   }
  [A-Za-z0-9_ ]* |
    .               { if (echo) ECHO; }
    "\n"            { if (echo) ECHO; aprepro.ap_file_list.top().lineno++; }
}

Becomes:

<VERBATIM>{
"{VERBATIM(OFF)}" { BEGIN(INITIAL);   }
[A-Za-z0-9_ ]* |
.               { if (do_echo) ECHO; }
"\n"            { if (do_echo) ECHO; aprepro.ap_file_list.top().lineno++; }
}

Generate scanner file:

reflex --bison --flex --outfile=apr_scanner.cc aprepro.ll

This will get you part of the way to using reflex. ¯

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