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Enhance LEMON to provide the ability to mark a rules as one that will never

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reduce due to intervention of actions.  Use this new capability to designate
the EXPLAIN rule as NEVER-REDUCES.

FossilOrigin-Name: 136cdefb2f7b582ff1771ac7f9e733dc24c357605526cbfb1834937697c8a922
This commit is contained in:
drh
2019-12-10 20:41:48 +00:00
parent 8e8c88964c
commit e94006eb42
4 changed files with 19 additions and 12 deletions
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13
tool/lemon.c
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@ -292,13 +292,15 @@ struct rule {
const char *code; /* The code executed when this rule is reduced */
const char *codePrefix; /* Setup code before code[] above */
const char *codeSuffix; /* Breakdown code after code[] above */
int noCode; /* True if this rule has no associated C code */
int codeEmitted; /* True if the code has been emitted already */
struct symbol *precsym; /* Precedence symbol for this rule */
int index; /* An index number for this rule */
int iRule; /* Rule number as used in the generated tables */
Boolean noCode; /* True if this rule has no associated C code */
Boolean codeEmitted; /* True if the code has been emitted already */
Boolean canReduce; /* True if this rule is ever reduced */
Boolean doesReduce; /* Reduce actions occur after optimization */
Boolean neverReduce; /* Reduce is theoretically possible, but prevented
** by actions or other outside implementation */
struct rule *nextlhs; /* Next rule with the same LHS */
struct rule *next; /* Next rule in the global list */
};
@ -2278,6 +2280,8 @@ fragment which begins on this line.");
"Code fragment beginning on this line is not the first \
to follow the previous rule.");
psp->errorcnt++;
}else if( strcmp(x, "{NEVER-REDUCE")==0 ){
psp->prevrule->neverReduce = 1;
}else{
psp->prevrule->line = psp->tokenlineno;
psp->prevrule->code = &x[1];
@ -4745,7 +4749,10 @@ void ReportTable(
assert( rp->noCode );
fprintf(out," /* (%d) ", rp->iRule);
writeRuleText(out, rp);
if( rp->doesReduce ){
if( rp->neverReduce ){
fprintf(out, " (NEVER REDUCES) */ assert(yyruleno!=%d);\n",
rp->iRule); lineno++;
}else if( rp->doesReduce ){
fprintf(out, " */ yytestcase(yyruleno==%d);\n", rp->iRule); lineno++;
}else{
fprintf(out, " (OPTIMIZED OUT) */ assert(yyruleno!=%d);\n",