-f with -b/-g generates incorrect dispatch on fill labels

[skvadrik]

Consider the following example 1.re:

/*!re2c
    "" {}
*/

With -if, re2c would generate correct dispatch:

$ re2c -if 1.re
/* Generated by re2c 0.14.3 on Tue Aug 25 10:41:45 2015 */


        switch (YYGETSTATE()) {
        default: goto yy0;
        case 0: goto yyFillLabel0;
        }
yy0:
        YYSETSTATE(0);
yyFillLabel0:
        {}

With -bif all positive YYGETSTATE() values will lead to yyFillLabel0, which is clearly an error: values that are greater than 0 should lead to yy0:

$ re2c -bif 1.re
/* Generated by re2c 0.14.3 on Tue Aug 25 10:40:32 2015 */


        if (YYGETSTATE() < 0) {
                goto yy0;
        } else {
                goto yyFillLabel0;
        }
yy0:
        YYSETSTATE(0);
yyFillLabel0:
        {}

With -gif the error is different: all values greater than 0 now cause undefined behaviour (access to memory not within array bounds):

$ re2c -gif 1.re
/* Generated by re2c 0.14.3 on Tue Aug 25 10:47:41 2015 */

{

        static void *yystable[] = {
                &&yyFillLabel0,
        };

        if (YYGETSTATE() < 0) {
                goto yy0;
        }
        goto *yystable[YYGETSTATE()];
yy0:
        YYSETSTATE(0);
yyFillLabel0:
        {}
}

The situation gets even more tricky if we add re2c:state:abort configuration (2.re):

/*!re2c
    re2c:state:abort = 1;
    "" {}
*/

Correct dispatch with -if looks like this:

$ re2c -if 2.re
/* Generated by re2c 0.14.3 on Tue Aug 25 10:51:35 2015 */


        switch (YYGETSTATE()) {
        default: abort();
        case -1: goto yy0;
        case 0: goto yyFillLabel0;
        }
yy0:
        YYSETSTATE(0);
yyFillLabel0:
        {}

With -bif call to abort() is unreachable:

$ re2c -bif 2.re
/* Generated by re2c 0.14.3 on Tue Aug 25 10:54:00 2015 */


        if (YYGETSTATE() < 0) {
                goto yy0;
        } else {
                goto yyFillLabel0;
        }
        abort();
yy0:
        YYSETSTATE(0);
yyFillLabel0:
        {}

With -gif we still get undefined behaviour for all values greater than 0:

$ re2c -gif 2.re
/* Generated by re2c 0.14.3 on Tue Aug 25 10:54:38 2015 */

{

        static void *yystable[] = {
                &&yyFillLabel0,
        };

        if (YYGETSTATE() == -1) {
                goto yy0;
        } else if (YYGETSTATE() < -1) {
                abort();
        }
        goto *yystable[YYGETSTATE()];
yy0:
        YYSETSTATE(0);
yyFillLabel0:
        {}
}

Besides, YYGETSTATE() macro is called multiple times with -b and -g, which is not so good. Additional checks with -g don't help either.

[skvadrik]

Fixed, see this commit. Now re2c with -f always generates simple switch.