Defines in rules block are not propagated to use blocks

[pwnalone]

Example

#include <assert.h>
#include <string.h>


/*!rules:re2c
    re2c:define:YYLIMIT  = lim;
    re2c:define:YYCURSOR = cur;
    re2c:define:YYMARKER = mrk;
    re2c:yych:emit = 0;
    re2c:define:YYGETCONDITION = 'condition';
    re2c:define:YYGETCONDITION:naked = 1;
    re2c:define:YYSETCONDITION = 'condition = @@;';
    re2c:define:YYSETCONDITION:naked = 1;
    re2c:yyfill:enable = 0;
    re2c:eof = 0;

    <init> *                                        { return -1; }
    <init> $                                        { return  0; }

    <init> [/][/] .*                                { goto loop; }
    <init> [/][*]                   :=> comment

    <init> [ \t]+                                   { goto loop; }

    <init, comment> [\n]+                           { goto loop; }

    <comment> [^*\n]+ [*]*          :=> comment
    <comment> [^*\n]* [*]+          :=> comment
    <comment> [^*\n]* [*]+ [/]       => init        { goto loop; }

    <comment> *                     :=> comment
    <comment> $                                     { return -1; }
*/


/*!types:re2c */

int lex(const char* cur)
{
    const char* lim;
    const char* mrk;

    char yych;

    int condition = yycinit;

    lim = cur + strlen(cur);
loop:
    mrk = cur;

    /*!use:re2c
        re2c:indent:top = 1;
        re2c:define:YYCTYPE = char;
    */
}


int main(void)
{
    assert(!lex("/* hello, */ // world !"));

    return 0;
}

Compile

re2c -W -Werror -c -r -o bug.c bug.re && gcc -o bug bug.c

Compilation Errors

The re2c:define:... commands in the !rules block are not propagated to the !use block, and so re2c ends up outputting the default identifiers instead. These are undeclared, so we end up with the following compilation errors:

bug.c: In function ‘lex’:
bug.c:34:10: error: ‘YYGETCONDITION’ undeclared (first use in this function)
   34 |  switch (YYGETCONDITION) {
      |          ^~~~~~~~~~~~~~
bug.c:34:10: note: each undeclared identifier is reported only once for each function it appears in
bug.c:42:10: error: ‘YYCURSOR’ undeclared (first use in this function)
   42 |  yych = *YYCURSOR;
      |          ^~~~~~~~
bug.c:49:7: error: ‘YYLIMIT’ undeclared (first use in this function)
   49 |   if (YYLIMIT <= YYCURSOR) goto yyeof2_init;
      |       ^~~~~~~
bug.c:88:2: error: ‘YYSETCONDITION’ undeclared (first use in this function)
   88 |  YYSETCONDITION
      |  ^~~~~~~~~~~~~~
bug.c:88:16: error: expected ‘;’ before ‘goto’
   88 |  YYSETCONDITION
      |                ^
      |                ;
   89 |  goto yyc_comment;
      |  ~~~~
bug.c:155:16: error: expected ‘;’ before ‘{’ token
  155 |  YYSETCONDITION
      |                ^
      |                ;
bug.c:113:3: error: label ‘yyeof2_comment’ used but not defined
  113 |   if (YYLIMIT <= YYCURSOR) goto yyeof2_comment;
      |   ^~

[skvadrik]

Hi @jinscoe123, this is a known issue. This behavior comes from old re2c versions and is kept for backwards compatibility. However, I agree that it is illogical and inconvenient, and I suspect that old re2c versions introduced this behavior accidentally. It is likely that no one really needs it. Given that I plan to release version 2.0 soon, I will likely make this backwards-incompatible change, and all configurations from rules block will be propagated to use blocks.

[pwnalone]

Okay, thank you! I appreciate your work toward this project, and I look forward to re2c v2.0!

[skvadrik]

The fix has been merged: b7e62a1. The above example compiles and runs without errors now.