lib: establish Zircon libc++ and KTL foundation

1 files changed, 53 insertions, 0 deletions

diff --git a/lib/ktl/include/cmath b/lib/ktl/include/cmath
new file mode 100644
index 0000000..13b8e6b
--- /dev/null
+++ b/lib/ktl/include/cmath
@@ -0,0 +1,53 @@
+// Copyright 2021 The Fuchsia Authors
+//
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT
+
+#ifndef ZIRCON_KERNEL_LIB_KTL_INCLUDE_CMATH_
+#define ZIRCON_KERNEL_LIB_KTL_INCLUDE_CMATH_
+
+// The kernel doesn't want this file but some libc++ headers we need
+// wind up including it.  They don't actually most of the math
+// declarations except under #if conditions that aren't true.
+
+#include <__config>
+#include <type_traits>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// These are used in templates that won't ever be instantiated in kernel code.
+
+template <typename T>
+constexpr bool isinf(T&& x) {
+  static_assert(!is_same_v<T, T>, "must not be instantiated in kernel code");
+  return false;
+}
+
+template <typename T>
+constexpr bool isnan(T&& x) {
+  static_assert(!is_same_v<T, T>, "must not be instantiated in kernel code");
+  return false;
+}
+
+template <typename T>
+constexpr bool signbit(T&& x) {
+  static_assert(!is_same_v<T, T>, "must not be instantiated in kernel code");
+  return false;
+}
+
+template <typename T>
+constexpr T frexp(T&& x, int* exponent) {
+  static_assert(!is_same_v<T, T>, "must not be instantiated in kernel code");
+  return x;
+}
+
+template <typename T>
+constexpr auto ceil(T&& x) {
+  static_assert(!is_same_v<T, T>, "must not be instantiated in kernel code");
+  return x;
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif  // ZIRCON_KERNEL_LIB_KTL_INCLUDE_CMATH_