lib: establish Zircon libc++ and KTL foundation

1 files changed, 23 insertions, 0 deletions

diff --git a/lib/ktl/include/wchar.h b/lib/ktl/include/wchar.h
new file mode 100644
index 0000000..b3f2ccb
--- /dev/null
+++ b/lib/ktl/include/wchar.h
@@ -0,0 +1,23 @@
+// Copyright 2023 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_WCHAR_H_
+#define ZIRCON_KERNEL_LIB_KTL_INCLUDE_WCHAR_H_
+
+// This file is included by <cstdio> and the like that are used from other
+// libc++ headers that are wrapped by ktl.  This file exists to preempt those
+// inclusions so that libc++'s <wchar.h> wrapper header won't be used, since
+// it's not compatible with the kernel environment.  However, other libc++
+// headers also use `#include_next <wchar.h>` to get to "the system libc"
+// version of the header.  To satisfy those, include-after/wchar.h provides the
+// actual declarations needed from the standard C <wchar.h> API.  So this
+// header just defers to that one, but must exist separately in this directory
+// so that it preempt's libc++'s wrapper.  This can't itself use #include_next
+// because that would reach libc++'s wrapper before the include-after file.
+
+#include "../include-after/wchar.h"
+
+#endif  // ZIRCON_KERNEL_LIB_KTL_INCLUDE_WCHAR_H_