Bug: %option main overrides %option yywrap

[John W. Millaway]

Hello,

There is a "bug" in the current version of flex (2.5.4) in which the %option
[no]main unconditionally sets the %option [no]yywrap. I use the term "bug"
hesitantly, because this behavior appears to be intentional. However, I can't 
think
of any use for it other than to cause unexpected link errors when yywrap() is 
not
found.

Example:

  %option noyywrap  /* Disable option yywrap. */
  %option nomain    /* Option yywrap is now enabled! */

One workaround is to always specify %option yywrap AFTER %option main. In 
general,
if the user explicitly sets an option, then flex should either honor that 
setting,
or report a conflict.

The bug is in "scan.l" at line 247, and is undocumented.

244:    lex-compat      lex_compat = option_sense;
245:    main            {
246:                    action_define( "YY_MAIN", option_sense );
247:                    do_yywrap = ! option_sense;
248:                    }
249:    meta-ecs        usemecs = option_sense;

-John Millaway


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