Developer CD Series 1994 November: Tool Chest/Dev.CD Nov 94.toast/Tool Chest/Development Tools & Languages/• Other Platforms/PCCTS/PCCTS last-minute bug fix

Text File | 1994-09-16 | 4.6 KB | 174 lines | [TEXT/????]

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From: [e-mail] (Terence Parr)
Subject: PCCTS 1.23 code gen fix
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Organization: AHPCRC, University of Minnesota, Minneapolis
Date: Wed, 14 Sep 1994 22:05:58 GMT
Lines: 159

It turns out that I introduced this (...)* code-gen bug back in 1.20.
I just happened to find it now.  For example, the following didn't
generate the right code:

a : ( A | B )* A C ;

Upon 'A C', a syntax error would occur.

Terribly sorry.  I'm in the process of adding parser exception handling
so will probably not put out a new release just for this bug fix.

Terence -------------------------------------

To fix things, just change the following functions in gen.c (PS: I
haven't had the time to test EVERYTHING with this fix.  Use at your
own risk ;).

/*
 * Generate code for a loop blk of form:
 *
 *                 |---|
 *                 v   |
 *               --o-G-o-->o--
 */
void
#ifdef __STDC__
genLoopBlk( Junction *begin, Junction *q, Junction *start, int max_k )
#else
genLoopBlk( begin, q, start, max_k )
Junction *begin;
Junction *q;
Junction *start;    /* where to start generating code from */
int max_k;
#endif
{
    set f;
    int need_right_curly;
    require(q->ntype == nJunction,    "genLoopBlk: not junction");
    require(q->jtype == aLoopBlk,    "genLoopBlk: not loop block");

    if ( q->visited ) return;
    q->visited = TRUE;
    if ( q->p2 == NULL )    /* only one alternative? */
    {
        if ( DemandLookahead )
            if ( !GenCC ) {gen1("LOOK(%d);\n", max_k);}
            else gen1("look(%d);\n", max_k);
        gen("while ( ");
        if ( begin!=NULL ) genExpr(begin);
        else genExpr(q);
        /* if no predicates have been hoisted for this single alt (..)*
         * do so now
         */
        if ( ParseWithPredicates && begin->predicate==NULL )
        {
            Predicate *a = find_predicates((Node *)q->p1);
            if ( a!=NULL )
            {
                _gen("&&");
                genPredTree(a, q);
            }
        }
        _gen(" ) {\n");
        tabs++;
        TRANS(q->p1);
        if ( !GenCC ) gen1("zzLOOP(zztasp%d);\n", BlkLevel-1);
        if ( DemandLookahead )
            if ( !GenCC ) {gen1("LOOK(%d);\n", max_k);}
            else gen1("look(%d);\n", max_k);
        --tabs;
        gen("}\n");
        freeBlkFsets(q);
        q->visited = FALSE;
        return;
    }
    else gen("while ( 1 ) {\n");
    tabs++;
    if ( begin!=NULL )
    {
        if ( DemandLookahead )
            if ( !GenCC ) {gen1("LOOK(%d);\n", max_k);}
            else gen1("look(%d);\n", max_k);
        gen("if ( ");
        genExpr((Junction *)begin->p2);
        _gen(" ) break;\n");
    }
    f = genBlk(q, aLoopBlk, &max_k, &need_right_curly);
    set_free(f);
    freeBlkFsets(q);

    /* generate code for terminating loop (this is optional branch) */
    if ( begin==NULL ) gen("else break;\n"); /* code for exiting loop "for sure" */

    { int i; for (i=1; i<=need_right_curly; i++) {tabs--; gen("}\n");} }
    if ( !GenCC ) gen1("zzLOOP(zztasp%d);\n", BlkLevel-1);
    --tabs;
    gen("}\n");
    q->visited = FALSE;
}

/*
 * Generate code for a loop blk of form:
 *
 *                          |---|
 *                         v   |
 *               --o-->o-->o-G-o-->o--
 *                   |           ^
 *                   v           |
 *                     o-----------o
 *
 * q->end points to the last node (far right) in the blk.  Note that q->end->jtype
 * must be 'EndBlk'.
 *
 * Generate code roughly of the following form:
 *
 *    do {
 *        ... code for alternatives ...
 *  } while ( First Set of aLoopBlk );
 *
 *    OR if > 1 alternative
 *
 *    do {
 *        ... code for alternatives ...
 *        else break;
 *  } while ( 1 );
 */
void
#ifdef __STDC__
genLoopBegin( Junction *q )
#else
genLoopBegin( q )
Junction *q;
#endif
{
    set f;
    int i;
    int max_k;
    require(q!=NULL,                "genLoopBegin: invalid node and/or rule");
    require(q->ntype == nJunction,    "genLoopBegin: not junction");
    require(q->jtype == aLoopBegin,    "genLoopBegin: not loop block");
    require(q->p2!=NULL,            "genLoopBegin: invalid Loop Graph");

    if ( GenLineInfo ) fprintf(output, LineInfoFormatStr, q->line, FileStr[q->file]);

    BLOCK_Preamble(q);
    BlkLevel++;
    f = First(q, 1, aLoopBegin, &max_k);
    /* If not simple LL(1), must specify to start at LoopBegin, not LoopBlk */
    if ( LL_k>1 && !set_nil(q->fset[2]) )
        genLoopBlk( q, (Junction *)q->p1, q, max_k );
    else genLoopBlk( q, (Junction *)q->p1, NULL, max_k );

    for (i=1; i<=CLL_k; i++) set_free(q->fset[i]);
    for (i=1; i<=CLL_k; i++) set_free(((Junction *)q->p2)->fset[i]);
    --BlkLevel;
    BLOCK_Tail();
    set_free(f);
    if (q->end->p1 != NULL) TRANS(q->end->p1);
}
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