/* 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;
}
/* Deallocates the expression tree.
*/
void freeexptree(struct exptree *t)
{
int n;
if (t) {
for (n = 0 ; n < t->childcount ; ++n)
freeexptree(t->child[n]);
deallocate(t);
}
}