[libcxx-commits] [libcxx] [libc++] Add a static_assert for a Mandates in seed_seq (PR #86992)

[Mark de Wever via libcxx-commits]

================
@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <random>
+
+// class seed_seq;
+
+// template<class RandomAccessIterator>
+//     void generate(RandomAccessIterator begin, RandomAccessIterator end);
+
+// Check the following requirement: https://eel.is/c++draft/rand.util.seedseq#7
+//
+//  Mandates: iterator_traits<RandomAccessIterator>​::​​value_type is an unsigned integer
+//            type capable of accommodating 32-bit quantities.
+
+// UNSUPPORTED: c++03
+// REQUIRES: stdlib=libc++
+
+#include <random>
+#include <climits>
+
+#include "test_macros.h"
+
+void f() {
+  std::seed_seq seq;
+
+  // Not an integral type
+  {
+    double* p = nullptr;
+    seq.generate(p, p); // expected-error-re@*:* {{static assertion failed{{.+}}: [rand.util.seedseq]/7 requires{{.+}}}}
+    // expected-error@*:* 0+ {{invalid operands to}}
+  }
+
+  // Not an unsigned type
+  {
+    long long* p = nullptr;
+    seq.generate(p, p); // expected-error-re@*:* {{static assertion failed{{.+}}: [rand.util.seedseq]/7 requires{{.+}}}}
+  }
+
+  // Not a 32-bit type
+  {
+    static_assert(sizeof(unsigned char) * CHAR_BIT < 32, "the test doesn't work on this platform");
----------------
mordante wrote:

Please use `std::uint32_t` here too.

Or maybe if this works with FileCheck.
```
#if UCHAR_MAX < UINT32_MAX
    unsigned char* p = nullptr;
    seq.generate(p, p); // expected-error-re@*:* {{static assertion failed{{.+}}: [rand.util.seedseq]/7 requires{{.+}}}}
#endif
```

https://github.com/llvm/llvm-project/pull/86992