Testcase for #1675.

test/val/bug1675-ub.c

@@ -0,0 +1,60 @@
+/* #1675 - Some UB cases of bit-shifts */
+
+#include <stdio.h>
+
+int unexpected = 0;
+
+void Test_UB(void)
+{
+    {
+        /* UB per standard, lhs expected in cc65: (int)-32768 */
+        if (!((0x4000 << 1) < 0)) {
+            ++unexpected;
+            printf("Expected: (0x4000 << 1) < 0, got lhs: %ld\n", (long)(0x4000 << 1));
+        }
+    }
+
+    {
+        /* UB per standard, lhs expected in cc65: (long)-2147483648L */
+        if (!((0x40000000 << 1) < 0)) {
+            ++unexpected;
+            printf("Expected: (0x40000000 << 1) < 0, got lhs: %ld\n", (long)(0x40000000 << 1));
+        }
+    }
+
+    {
+        /* UB per standard, lhs expected in cc65: (int)-32768 */
+        if (!(((unsigned char)0x80 << 8) < 0)) {
+            ++unexpected;
+            printf("Expected: ((unsigned char)0x80 << 8) < 0, got lhs: %ld\n", (long)((unsigned char)0x80 << 8));
+        }
+    }
+
+    {
+        /* UB per standard, lhs expected in cc65: (int)-32768 */
+        if (!(((short)0x4000L << 1) < 0)) {
+            ++unexpected;
+            printf("Expected: ((short)0x4000L << 1) < 0, got lhs: %ld\n", (long)((short)0x4000L << 1));
+        }
+    }
+
+    {
+        const signed short x = 0x4000;
+        /* UB per standard, lhs expected in cc65: (int)-32768 */
+        if (!((x << 1) < 0)) {
+            ++unexpected;
+            printf("Expected: (x << 1) < 0, got lhs: %ld\n", (long)(x << 1));
+        }
+    }
+}
+
+int main(void)
+{
+    Test_UB();
+
+    if (unexpected != 0) {
+        printf("Unexpected: %d\n", unexpected);
+    }
+
+    return unexpected;
+}