[libcamera-devel] [PATCH 1/2] libcamera: Add macro to conditionally use [[nodiscard]]

[Laurent Pinchart]

The [[nodiscard]] attribute has been added to C++17. It can thus be used
inside libcamera, but would prevent applications compiled for C++14 to
use libcamera if the attribute was used in public headers.

To offer this feature when the application is compiled with a
recent-enough C++ version, as well as for compiling libcamera itself,
add a __nodiscard macro that expands as [[nodiscard]] when using C++17
or newer.

Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 include/libcamera/compiler.h  | 16 ++++++++++++++++
 include/libcamera/meson.build |  1 +
 2 files changed, 17 insertions(+)
 create mode 100644 include/libcamera/compiler.h

diff --git a/include/libcamera/compiler.h b/include/libcamera/compiler.h
new file mode 100644
index 000000000000..dc56dbb8b792
--- /dev/null
+++ b/include/libcamera/compiler.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Google Inc.
+ *
+ * compiler.h - Compiler support
+ */
+#ifndef __LIBCAMERA_COMPILER_H__
+#define __LIBCAMERA_COMPILER_H__
+
+#if __cplusplus >= 201703L
+#define __nodiscard		[[nodiscard]]
+#else
+#define __nodiscard
+#endif
+
+#endif /* __LIBCAMERA_COMPILER_H__ */
diff --git a/include/libcamera/meson.build b/include/libcamera/meson.build
index cf2935f1ee95..13e9eeb6d6ad 100644
--- a/include/libcamera/meson.build
+++ b/include/libcamera/meson.build
@@ -5,6 +5,7 @@ libcamera_public_headers = files([
     'buffer.h',
     'camera.h',
     'camera_manager.h',
+    'compiler.h',
     'controls.h',
     'extensible.h',
     'file_descriptor.h',
-- 
Regards,

Laurent Pinchart