[C99] Claim conformance to WG14 N570

clang/test/C/C99/n570.c

@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 -verify -std=c99 %s
+// RUN: %clang_cc1 -E -std=c99 %s | FileCheck %s
+// expected-no-diagnostics
+
+/* WG14 N570: Yes
+ * Empty macro arguments
+ *
+ * NB: the original paper is not available online anywhere, so the test
+ * coverage is coming from what could be gleaned from the C99 rationale
+ * document. In C89, it was UB to pass no arguments to a function-like macro,
+ * and that's now supported in C99.
+ */
+
+#define TEN 10
+#define U u
+#define I // expands into no preprocessing tokens
+#define L L
+#define glue(a, b) a ## b
+#define xglue(a, b) glue(a, b)
+
+const unsigned u = xglue(TEN, U);
+const int i = xglue(TEN, I);
+const long l = xglue(TEN, L);
+
+// CHECK: const unsigned u = 10u;
+// CHECK-NEXT: const int i = 10;
+// CHECK-NEXT: const long l = 10L;
+
+_Static_assert(u == 10U, "");
+_Static_assert(i == 10, "");
+_Static_assert(l == 10L, "");

clang/www/c_status.html

@@ -300,7 +300,7 @@ <h2 id="c99">C99 implementation status</h2>
     <tr>
       <td>empty macro arguments</td>
       <td>N570</td>
-      <td class="unknown" align="center">Unknown</td>
+      <td class="full" align="center">Yes</td>
     </tr>
     <tr>
       <td>new structure type compatibility (tag compatibility)</td>