lib: cpp: Relocate subsys/cpp to lib/cpp

This commit moves the files under `subsys/cpp` directory to the
`lib/cpp` directory because the C++ ABI runtime library and the
standard C++ library components are not a "subsystem" (aka. API) in
conventional sense and is better described as a "library."

Classifying the C++ ABI runtime library and the standard C++ library as
"libraries" instead of "subsystems" also better aligns with how the
existing C standard library implementation (`lib/libc`) is handled.

Signed-off-by: Stephanos Ioannidis <stephanos.ioannidis@nordicsemi.no>

MAINTAINERS.yml

@@ -286,9 +286,9 @@ Build system:
     - alexanderwachter
     - cfriedt
   files:
-    - subsys/cpp/
-    - tests/subsys/cpp/
-    - samples/subsys/cpp/
+    - lib/cpp/
+    - tests/lib/cpp/
+    - samples/cpp/
   labels:
     - "area: C++"
 

doc/develop/languages/cpp/index.rst

@@ -63,19 +63,19 @@ In order to make use of the C++ exceptions, the
 :kconfig:option:`CONFIG_EXCEPTIONS` must be selected in the application
 configuration file.
 
-Zephyr C++ Subsystem
-********************
+Zephyr Minimal C++ Library
+**************************
 
-Zephyr C++ subsystem (:file:`subsys/cpp`) provides a minimal subset of the C++
-standard library and application binary interface (ABI) functions to enable
-basic C++ language support. This includes:
+Zephyr minimal C++ library (:file:`lib/cpp/minimal`) provides a minimal subset
+of the C++ standard library and application binary interface (ABI) functions to
+enable basic C++ language support. This includes:
 
 * ``new`` and ``delete`` operators
 * virtual function stub and vtables
 * static global initializers for global constructors
 
-The scope of the C++ subsystem is strictly limited to providing the basic C++
-language support, and it does not implement any `Standard Template Library
+The scope of the minimal C++ library is strictly limited to providing the basic
+C++ language support, and it does not implement any `Standard Template Library
 (STL)`_ classes and functions. For this reason, it is only suitable for use in
 the applications that implement their own (non-standard) class library and do
 rely on the Standard Template Library (STL) components.

lib/CMakeLists.txt

@@ -4,6 +4,7 @@ if(NOT CONFIG_EXTERNAL_LIBC)
 add_subdirectory(libc)
 add_subdirectory(posix)
 endif()
+add_subdirectory_ifdef(CONFIG_CPLUSPLUS            cpp)
 add_subdirectory(os)
 add_subdirectory(util)
 add_subdirectory_ifdef(CONFIG_SMF smf)

lib/Kconfig

@@ -3,6 +3,8 @@
 
 source "lib/libc/Kconfig"
 
+source "lib/cpp/Kconfig"
+
 menu "Additional libraries"
 
 source "lib/os/Kconfig"

subsys/CMakeLists.txt

@@ -6,7 +6,6 @@ add_subdirectory_ifdef(CONFIG_LORAWAN              lorawan)
 add_subdirectory_ifdef(CONFIG_BT                   bluetooth)
 add_subdirectory_ifdef(CONFIG_CONSOLE_SUBSYS       console)
 add_subdirectory_ifdef(CONFIG_SHELL                shell)
-add_subdirectory_ifdef(CONFIG_CPLUSPLUS            cpp)
 add_subdirectory_ifdef(CONFIG_DISK_ACCESS          disk)
 add_subdirectory_ifdef(CONFIG_EMUL emul)
 add_subdirectory(fs)

subsys/Kconfig

@@ -12,8 +12,6 @@ source "subsys/canbus/Kconfig"
 
 source "subsys/console/Kconfig"
 
-source "subsys/cpp/Kconfig"
-
 source "subsys/debug/Kconfig"
 
 source "subsys/disk/Kconfig"