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392f3caef6
The option --header was introduced in version 2.5.6. The option --header-file was introduced in version 2.6.4. Reported by Bruno Haible. https://lists.gnu.org/r/bug-bison/2020-05/msg00013.html So use --header, and do bother with versions that don't support it. * m4/flex.m4: Check whether flex supports --header. * configure.ac (FLEX_WORKS, FLEX_CXX_WORKS): Set to false if it doesn't. * * examples/c/reccalc/local.mk, examples/c/reccalc/Makefile: Use --header rather than --header-file.
reccalc - recursive calculator with Flex and Bison
In this example the generated parser is pure and reentrant: it can be used concurrently in different threads, or recursively. As a proof of this reentrancy, expressions in parenthesis are tokenized as strings, and then recursively parsed from the parser:
exp: STR
{
result r = parse_string ($1);
free ($1);
if (r.nerrs)
{
res->nerrs += r.nerrs;
YYERROR;
}
else
$$ = r.value;
}