================
@@ -0,0 +1,61 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c2y -pedantic -Wall -Wno-comment -verify
%s
+
+/* WG14 N3369: Clang 21
+ * _Lengthof operator
+ *
+ * Adds an operator to get the length of an array. Note that WG14 N3469 renamed
+ * this operator to _Countof.
+ */
+
+int global_array[12];
+
+void test_parsing_failures() {
+ (void)_Countof; // expected-error {{expected expression}}
+ (void)_Countof(; // expected-error {{expected expression}}
+ (void)_Countof(); // expected-error {{expected expression}}
+ (void)_Countof int; // expected-error {{expected expression}}
+}
+
+void test_semantic_failures() {
+ (void)_Countof(1); // expected-error {{'_Countof' requires an
argument of array type; 'int' invalid}}
+ int non_array;
+ (void)_Countof non_array; // expected-error {{'_Countof' requires an
argument of array type; 'int' invalid}}
+ (void)_Countof(int); // expected-error {{'_Countof' requires an
argument of array type; 'int' invalid}}
+}
+
+void test_constant_expression_behavior(int n) {
+ static_assert(_Countof(global_array) == 12);
+ static_assert(_Countof global_array == 12);
+ static_assert(_Countof(int[12]) == 12);
+
+ // Use of a VLA makes it not a constant expression, same as with sizeof.
+ int array[n];
+ static_assert(_Countof(array)); // expected-error {{static assertion
expression is not an integral constant expression}}
+ static_assert(sizeof(array)); // expected-error {{static assertion
expression is not an integral constant expression}}
+ static_assert(_Countof(int[n]));// expected-error {{static assertion
expression is not an integral constant expression}}
+ static_assert(sizeof(int[n])); // expected-error {{static assertion
expression is not an integral constant expression}}
+
+ // Constant folding works the same way as sizeof, too.
+ const int m = 12;
+ int other_array[m];
+ static_assert(sizeof(other_array)); // expected-error {{static assertion
expression is not an integral constant expression}}
+ static_assert(_Countof(other_array)); // expected-error {{static assertion
expression is not an integral constant expression}}
+ static_assert(sizeof(int[m])); // expected-error {{static assertion
expression is not an integral constant expression}}
+ static_assert(_Countof(int[m])); // expected-error {{static assertion
expression is not an integral constant expression}}
+
+ // Note that this applies to each array dimension.
+ int another_array[n][7];
+ static_assert(_Countof(another_array)); // expected-error {{static assertion
expression is not an integral constant expression}}
+ static_assert(_Countof(*another_array) == 7);
+}
+
+void test_with_function_param(int array[12], int (*array_ptr)[12]) {
----------------
jyknight wrote:
I presume `void fn(int array[static 12])` also doesn't work, as it also doesn't
get an array type then (which always seemed really odd to me but _shrug_.)
https://github.com/llvm/llvm-project/pull/133125
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