constant expressions: c precedence and / % ^ (b.1.3); local const usable in constant expressions (b.1.7, b.2.16); zc0 matches

1 files changed, 33 insertions, 7 deletions

diff --git a/src/tools/zc0.c b/src/tools/zc0.c
index 6c62abf..229734c 100644
--- a/src/tools/zc0.c
+++ b/src/tools/zc0.c
@@ -396,16 +396,42 @@ static int64_t cprim(void)
 	if (tk == T_ID && (s = find(ts)) && (s->kind == K_CONST || (s->kind != K_GVAR && s->defd))) { next(); return s->val; }
 	die("constant expected"); return 0;
 }
-static int64_t cexpr(void)
+/* c precedence (spec 3.14.1): * / % above + -, above << >>, above &, ^, | */
+static int cprec(void)
 {
-	int64_t v = cprim();
-	for (;;) {
-		if (accept("+")) v += cprim(); else if (accept("-")) v -= cprim();
-		else if (accept("*")) v *= cprim(); else if (accept("|")) v |= cprim();
-		else if (accept("&")) v &= cprim(); else if (accept("<<")) v <<= cprim();
-		else if (accept(">>")) v >>= cprim(); else return v;
+	if (is("*") || is("/") || is("%")) return 10;
+	if (is("+") || is("-")) return 9;
+	if (is("<<") || is(">>")) return 8;
+	if (is("&")) return 5;
+	if (is("^")) return 4;
+	if (is("|")) return 3;
+	return 0;
+}
+static int64_t cbin(int minp)
+{
+	int64_t v = cprim(), w; int p; char o[3];
+	while ((p = cprec()) && p >= minp) {
+		o[0] = ts[0]; o[1] = ts[1]; o[2] = 0;
+		next(); w = cbin(p + 1);
+		switch (o[0]) {
+		case '*': v *= w; break;
+		case '/': case '%':
+			if (w == 0) { die("division by zero in a constant expression"); return 0; }
+			if (w == -1) v = o[0] == '/' ? (int64_t)(0 - (uint64_t)v) : 0;
+			else v = o[0] == '/' ? v / w : v % w;
+			break;
+		case '+': v += w; break;
+		case '-': v -= w; break;
+		case '<': v = (int64_t)((uint64_t)v << (w & 63)); break;
+		case '>': v >>= (w & 63); break;
+		case '&': v &= w; break;
+		case '^': v ^= w; break;
+		default: v |= w; break;
+		}
 	}
+	return v;
 }
+static int64_t cexpr(void) { return cbin(1); }
 
 /* ---- types ----
    zc0 has no types: a type is read and thrown away. all it has to know is the