Fix _Alignas

* don't accept _Alignas as type qualifier (after pointer '*').
* accept type-names within _Alignas
* add testcases

tccgen.c

@@ -4176,20 +4176,25 @@ static int parse_btype(CType *type, AttributeDef *ad)
             goto basic_type;
         case TOK_ALIGNAS:
             { int n;
-            next();
+              AttributeDef ad1;
-            /* TODO: _Alignas(type) -> _Alignas(_Alignof(type)) */
+              next();
-            if (tok == '(') {
+              skip('(');
-                next();
+              memset(&ad1, 0, sizeof(AttributeDef));
-                n = expr_const();
+              if (parse_btype(&type1, &ad1)) {
-                if (n <= 0 || (n & (n - 1)) != 0)
+                  type_decl(&type1, &ad1, &n, TYPE_ABSTRACT);
+                  if (ad1.a.aligned)
+                    n = 1 << (ad1.a.aligned - 1);
+                  else
+                    type_size(&type1, &n);
+              } else {
+                  n = expr_const();
+                  if (n <= 0 || (n & (n - 1)) != 0)
                     tcc_error("alignment must be a positive power of two");
-                skip(')');
+              }
-            } else {
+              skip(')');
-                 expect("(");
+              ad->a.aligned = exact_log2p1(n);
             }
-            ad->a.aligned = exact_log2p1(n);
+            continue;
-          }
-          continue;
         case TOK_LONG:
             if ((t & VT_BTYPE) == VT_DOUBLE) {
                 t = (t & ~(VT_BTYPE|VT_LONG)) | VT_LDOUBLE;
@@ -4594,22 +4599,6 @@ static CType *type_decl(CType *type, AttributeDef *ad, int *v, int td)
         case TOK_RESTRICT2:
         case TOK_RESTRICT3:
             goto redo;
-        case TOK_ALIGNAS:
-            { int n;
-            next();
-            /* TODO: _Alignas(type) -> _Alignas(_Alignof(type)) */
-            if (tok == '(') {
-                next();
-                n = expr_const();
-                if (n <= 0 || (n & (n - 1)) != 0)
-                    tcc_error("alignment must be a positive power of two");
-                skip(')');
-            } else {
-                expect("(");
-            }
-            ad->a.aligned = exact_log2p1(n);
-          }
-          break;
 	/* XXX: clarify attribute handling */
 	case TOK_ATTRIBUTE1:
 	case TOK_ATTRIBUTE2:

tests/tests2/102_alignas.c

@@ -0,0 +1,28 @@
+_Alignas(16) int i1;
+int _Alignas(16) i2;
+void _Alignas(16) *p2;
+_Alignas(16) i3;
+int _Alignas(double) i4;
+int _Alignas(int) i5;
+#if 0
+/* The following are currently wrongly accepted by TCC but really shouldn't.  */
+int _Alignas(int _Alignas(16)) i6; //wrong, 'int _Alignas(16)' is no type-name
+typedef int _Alignas(16) int16aligned_t; //wrong, _Alignas invalid on typedef
+int16aligned_t i7;
+#endif
+/* i8 should get an alignment of 16, because unlike _Alignas the
+   corresponding attribute _does_ apply to type-name, though not in
+   some clang versions.  */
+int _Alignas(int __attribute__((aligned(16)))) i8;
+extern int printf(const char*, ...);
+#ifdef _MSC_VER
+#define alignof(x) (int)__alignof(x)
+#else
+#define alignof(x) (int)__alignof__(x)
+#endif
+int main()
+{
+  printf("%d %d %d %d\n",
+         alignof(i1), alignof(i4), alignof(i5), alignof(i8));
+  return 0;
+}

tests/tests2/102_alignas.expect

@@ -0,0 +1 @@
+16 8 4

tests/tests2/60_errors_and_warnings.c

@@ -172,4 +172,7 @@ int X=1;
 int main(void) {
   int t[][][X];
 }
+#elif defined test_invalid_alignas
+/* _Alignas is no type qualifier */
+void * _Alignas(16) p1;
 #endif

tests/tests2/60_errors_and_warnings.expect

@@ -80,3 +80,6 @@
 
 [test_vla_1]
 60_errors_and_warnings.c:173: error: need explicit inner array size in VLAs
+
+[test_invalid_alignas]
+60_errors_and_warnings.c:177: error: identifier expected