/* Partially preprocesses a #if expression. ifexp points to the text
* immediately following the #if. The function seeks to the end of the
* expression and evaluates it. The return value points to the text
* immediately following the expression. If the expression has a
* defined state, status receives either statDefined or statUndefined.
* If the expression's contents are disjoint from the defined and
* undefined symbols, status receives statUnaffected. Otherwise the
* expression is in a partial state, in which case status receives
* statPartDefined, and the original string is modified so as to
* remove the parts of the expression that have a defined state.
*/
static char const *seqif(struct ppproc *ppp, char *ifexp, enum status *status)
{
struct exptree *tree;
char const *ret;
char *str;
int defined, n;
tree = initexptree();
*status = statUnaffected;
n = geterrormark();
ret = parseexptree(tree, ppp->cl, ifexp);
if (errorsincemark(n)) {
*status = statError;
goto quit;
}
n = markdefined(tree, ppp->defs, TRUE) +
markdefined(tree, ppp->undefs, FALSE);
if (n) {
*status = evaltree(tree, &defined) ? statDefined : statUndefined;
if (!defined) {
*status = statPartDefined;
str = allocate(strlen(ifexp) + 1);
n = unparseevaluated(tree, str);
strcpy(str + n, ifexp + getexplength(tree));
strcpy(ifexp, str);
deallocate(str);
}
}
quit:
freeexptree(tree);
return ret;
}
/* Recursively examines an expression tree and sets the definition
* state of any identifiers within that appear in the given symset.
* The third parameter indicates whether the identifiers are to be
* treated as defined or as undefined.
*/
int markdefined(struct exptree *t, struct symset *set, int defined)
{
long value;
int count, n;
count = 0;
for (n = 0 ; n < t->childcount ; ++n)
count += markdefined(t->child[n], set, defined);
if (!t->valued) {
if (t->exp == expDefined) {
if (findsymbolinset(set, t->identifier, NULL)) {
t->valued = TRUE;
t->value = defined ? 1 : 0;
++count;
}
} else if (t->exp == expMacro) {
if (findsymbolinset(set, t->begin, &value)) {
t->valued = TRUE;
t->value = defined ? value : 0;
++count;
}
}
}
return count;
}
