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Change the coverage measurement logic in the lemon-generated parser so that

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it only checks for coverage of state/lookahead pairs that are valid syntax.
It turns out that some states are unreachable if the lookahead is not valid
syntax, because the states are only reachable through a shift following a
reduce, and the reduce does not happen if the lookahead is a syntax error.

FossilOrigin-Name: 9dce46508772bd0f9e940c4d44933154044bb58c1b3511dd0143287bf795dd6b
This commit is contained in:
drh
2017-12-27 17:14:50 +00:00
parent 7e7b753158
commit 7038a991b0
3 changed files with 23 additions and 17 deletions
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26
tool/lempar.c
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@ -467,20 +467,25 @@ static unsigned char yycoverage[YYNSTATE][YYNTOKEN];
/*
** Write into out a description of every state/lookahead combination that
** has not previously been seen by the parser. Return the number of
** missed state/lookahead combinations.
**
** (1) has not been used by the parser, and
** (2) is not a syntax error.
**
** Return the number of missed state/lookahead combinations.
*/
#if defined(YYCOVERAGE)
int ParseCoverage(FILE *out){
int i, j;
int stateno, iLookAhead, i;
int nMissed = 0;
for(i=0; i<YYNSTATE; i++){
for(j=1; j<YYNTOKEN; j++){
if( j==YYWILDCARD ) continue;
if( !yycoverage[i][j] ) nMissed++;
for(stateno=0; stateno<YYNSTATE; stateno++){
i = yy_shift_ofst[stateno];
for(iLookAhead=0; iLookAhead<YYNTOKEN; iLookAhead++){
if( yy_lookahead[i]!=iLookAhead ) continue;
if( yycoverage[stateno][iLookAhead]==0 ) nMissed++;
if( out ){
fprintf(out,"State %d lookahead %s %s\n",
i, yyTokenName[j], yycoverage[i][j] ? "ok" : "missed");
fprintf(out,"State %d lookahead %s %s\n", stateno,
yyTokenName[iLookAhead],
yycoverage[stateno][iLookAhead] ? "ok" : "missed");
}
}
}
@ -506,9 +511,10 @@ static unsigned int yy_find_shift_action(
#endif
do{
i = yy_shift_ofst[stateno];
assert( i>=0 && i+YYNTOKEN<=sizeof(yy_lookahead)/sizeof(yy_lookahead[0]) );
assert( iLookAhead!=YYNOCODE );
assert( iLookAhead < YYNTOKEN );
i += iLookAhead;
assert( i>=0 && i<sizeof(yy_lookahead)/sizeof(yy_lookahead[0]) );
if( yy_lookahead[i]!=iLookAhead ){
#ifdef YYFALLBACK
YYCODETYPE iFallback; /* Fallback token */