+static inline int ftepp_next(ftepp_t *ftepp)
+{
+ return (ftepp->token = lex_do(ftepp->lex));
+}
+
+/* Important: this does not skip newlines! */
+static bool ftepp_skipspace(ftepp_t *ftepp)
+{
+ while (ftepp_next(ftepp) == TOKEN_WHITE) {}
+ return (ftepp->token < TOKEN_EOF);
+}
+
+static bool ftepp_if(ftepp_t *ftepp, ppcondition *cond)
+{
+ ftepp_error(ftepp, "TODO: #if");
+ return false;
+}
+
+static bool ftepp_ifdef(ftepp_t *ftepp, ppcondition *cond)
+{
+ ftepp_error(ftepp, "TODO: #ifdef");
+ return false;
+}
+
+static bool ftepp_define(ftepp_t *ftepp)
+{
+ ftepp_error(ftepp, "TODO: #define");
+ return false;
+}
+
+static bool ftepp_else_allowed(ftepp_t *ftepp)
+{
+ if (!vec_size(ftepp->conditions)) {
+ ftepp_error(ftepp, "#else without #if");
+ return false;
+ }
+ if (vec_last(ftepp->conditions).had_else) {
+ ftepp_error(ftepp, "multiple #else for a single #if");
+ return false;
+ }
+ return true;
+}
+
+static bool ftepp_hash(ftepp_t *ftepp)
+{
+ ppcondition cond;
+ ppcondition *pc;
+
+ lex_ctx ctx = ftepp_ctx(ftepp);
+
+ if (!ftepp_skipspace(ftepp))
+ return false;
+
+ switch (ftepp->token) {
+ case TOKEN_IDENT:
+ if (!strcmp(ftepp_tokval(ftepp), "define")) {
+ return ftepp_define(ftepp);
+ }
+ else if (!strcmp(ftepp_tokval(ftepp), "ifdef")) {
+ if (!ftepp_ifdef(ftepp, &cond))
+ return false;
+ vec_push(ftepp->conditions, cond);
+ return true;
+ }
+ else if (!strcmp(ftepp_tokval(ftepp), "ifndef")) {
+ if (!ftepp_ifdef(ftepp, &cond))
+ return false;
+ cond.on = !cond.on;
+ vec_push(ftepp->conditions, cond);
+ return true;
+ }
+ else if (!strcmp(ftepp_tokval(ftepp), "elifdef")) {
+ if (!ftepp_else_allowed(ftepp))
+ return false;
+ if (!ftepp_ifdef(ftepp, &cond))
+ return false;
+ pc = &vec_last(ftepp->conditions);
+ pc->on = !pc->was_on && cond.on;
+ pc->was_on = pc->was_on || pc->on;
+ return true;
+ }
+ else if (!strcmp(ftepp_tokval(ftepp), "elifndef")) {
+ if (!ftepp_else_allowed(ftepp))
+ return false;
+ if (!ftepp_ifdef(ftepp, &cond))
+ return false;
+ cond.on = !cond.on;
+ pc = &vec_last(ftepp->conditions);
+ pc->on = !pc->was_on && cond.on;
+ pc->was_on = pc->was_on || pc->on;
+ return true;
+ }
+ else if (!strcmp(ftepp_tokval(ftepp), "elif")) {
+ if (!ftepp_else_allowed(ftepp))
+ return false;
+ if (!ftepp_if(ftepp, &cond))
+ return false;
+ pc = &vec_last(ftepp->conditions);
+ pc->on = !pc->was_on && cond.on;
+ pc->was_on = pc->was_on || pc->on;
+ return true;
+ }
+ else if (!strcmp(ftepp_tokval(ftepp), "if")) {
+ if (!ftepp_if(ftepp, &cond))
+ return false;
+ vec_push(ftepp->conditions, cond);
+ return true;
+ }
+ else if (!strcmp(ftepp_tokval(ftepp), "else")) {
+ if (!ftepp_else_allowed(ftepp))
+ return false;
+ pc = &vec_last(ftepp->conditions);
+ pc->on = !pc->was_on;
+ pc->had_else = true;
+ return true;
+ }
+ else if (!strcmp(ftepp_tokval(ftepp), "endif")) {
+ if (!vec_size(ftepp->conditions)) {
+ ftepp_error(ftepp, "#endif without #if");
+ return false;
+ }
+ vec_pop(ftepp->conditions);
+ break;
+ }
+ else {
+ ftepp_error(ftepp, "unrecognized preprocessor directive: `%s`", ftepp_tokval(ftepp));
+ return false;
+ }
+ break;
+ case TOKEN_KEYWORD:
+ if (!strcmp(ftepp_tokval(ftepp), "if")) {
+ if (!ftepp_if(ftepp, &cond))
+ return false;
+ vec_push(ftepp->conditions, cond);
+ return true;
+ }
+ /* fall through */
+ default:
+ ftepp_error(ftepp, "unexpected preprocessor token: `%s`", ftepp_tokval(ftepp));
+ return false;
+ case TOKEN_EOL:
+ ftepp_errorat(ftepp, ctx, "empty preprocessor directive");
+ return false;
+ case TOKEN_EOF:
+ ftepp_error(ftepp, "missing newline at end of file", ftepp_tokval(ftepp));
+ return false;
+ }
+ return true;
+}
+