oe-selftest: add a cpp-example recipe

This simple C++ project supports compilation with CMake and Meson.
(Autotool support could be added later on.)
It's supposed to be used with oe-selftest.

An artificial project has several advantages over compiling a normal
CMake or Meson based project for testing purposes:
- It is much faster because it can be kept minimalistic
- It can cover multiple odd corner cases
- No one will change it in an unpredictable way
- It can support multiple build tools with only one C++ codebase

(From OE-Core rev: 4904e772470b0d6e5d98ef0344b3f2bf54214661)

Signed-off-by: Adrian Freihofer <adrian.freihofer@siemens.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-selftest/recipes-test/cpp/.gitignore

@@ -0,0 +1 @@
+build*

meta-selftest/recipes-test/cpp/cmake-example.bb

@@ -0,0 +1,25 @@
+#
+# Copyright OpenEmbedded Contributors
+#
+# SPDX-License-Identifier: MIT
+#
+
+SUMMARY = "A C++ example compiled with cmake."
+
+require cpp-example.inc
+
+SRC_URI += "file://CMakeLists.txt"
+
+inherit cmake-qemu
+
+PACKAGECONFIG[failing_test] = "-DFAILING_TEST=ON"
+
+FILES:${PN}-ptest += "${bindir}/test-cmake-example"
+
+do_run_tests () {
+    bbnote ${DESTDIR:+DESTDIR=${DESTDIR} }${CMAKE_VERBOSE} cmake --build '${B}' --target test -- ${EXTRA_OECMAKE_BUILD}
+    eval ${DESTDIR:+DESTDIR=${DESTDIR} }${CMAKE_VERBOSE} cmake --build '${B}' --target test -- ${EXTRA_OECMAKE_BUILD}
+}
+do_run_tests[doc] = "Run cmake --target=test using qemu-user"
+
+addtask do_run_tests after do_compile

meta-selftest/recipes-test/cpp/cmake-example/run-ptest

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+#!/bin/sh
+#
+# Copyright OpenEmbedded Contributors
+#
+# SPDX-License-Identifier: MIT
+#
+
+test-cmake-example
+
+# Note: run-ptests exits with exit value from test-cmake-example

meta-selftest/recipes-test/cpp/cpp-example.inc

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+#
+# Copyright OpenEmbedded Contributors
+#
+# SPDX-License-Identifier: MIT
+#
+
+LICENSE = "MIT"
+LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"
+
+DEPENDS += "json-c"
+
+PV = "1.0"
+
+SRC_URI = "\
+    file://cpp-example.cpp \
+    file://cpp-example-lib.hpp \
+    file://cpp-example-lib.cpp \
+    file://test-cpp-example.cpp \
+    file://run-ptest \
+"
+
+S = "${WORKDIR}"
+
+inherit ptest

meta-selftest/recipes-test/cpp/files/CMakeLists.txt

@@ -0,0 +1,61 @@
+#
+# Copyright OpenEmbedded Contributors
+#
+# SPDX-License-Identifier: MIT
+#
+
+cmake_minimum_required(VERSION 3.22)
+
+project(cmake-example
+  VERSION 1.0.0
+  LANGUAGES CXX
+)
+
+option(BUILD_SHARED_LIBS "Build using shared libraries" ON)
+option(FAILING_TEST "Compile a failing unit test to test the test infrastructure" OFF)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED On)
+set(CMAKE_CXX_EXTENSIONS Off)
+
+include(GNUInstallDirs)
+
+# Linking a small library makes the example more useful for testing.
+find_package(json-c)
+
+# A simple library linking json-c library found by pkgconfig
+add_library(cmake-example-lib cpp-example-lib.cpp cpp-example-lib.hpp)
+set_target_properties(cmake-example-lib PROPERTIES 
+    VERSION ${PROJECT_VERSION}
+    SOVERSION ${PROJECT_VERSION_MAJOR}
+)
+target_link_libraries(cmake-example-lib PRIVATE json-c::json-c)
+
+install(TARGETS cmake-example-lib
+    INCLUDES DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
+    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+)
+
+# A simple executable linking the library
+add_executable(cmake-example cpp-example.cpp)
+target_link_libraries(cmake-example PRIVATE cmake-example-lib)
+
+install(TARGETS cmake-example
+    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
+)
+
+# A simple test executable for testing the library
+add_executable(test-cmake-example test-cpp-example.cpp)
+target_link_libraries(test-cmake-example PRIVATE cmake-example-lib)
+
+if (FAILING_TEST)
+    target_compile_definitions(test-cmake-example PRIVATE FAIL_COMPARISON_STR="foo")
+endif(FAILING_TEST)
+
+install(TARGETS test-cmake-example
+    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
+)
+
+include(CTest)
+add_test(NAME test-cmake-example COMMAND test-cmake-example)

meta-selftest/recipes-test/cpp/files/cpp-example-lib.cpp

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+/*
+ * Copyright OpenEmbedded Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <iostream>
+#include <string>
+#include <json-c/json.h>
+#include "cpp-example-lib.hpp"
+
+const std::string &CppExample::get_string()
+{
+    return test_string;
+}
+
+const char *CppExample::get_json_c_version()
+{
+    return json_c_version();
+}
+
+void CppExample::print_json()
+{
+    struct json_object *jobj;
+    const int flag = JSON_C_TO_STRING_SPACED | JSON_C_TO_STRING_PRETTY;
+
+    jobj = json_object_new_object();
+    json_object_object_add(jobj, "test_string", json_object_new_string(test_string.c_str()));
+
+    std::cout << json_object_to_json_string_ext(jobj, flag) << std::endl;
+
+    json_object_put(jobj); // Delete the json object
+}

meta-selftest/recipes-test/cpp/files/cpp-example-lib.hpp

@@ -0,0 +1,21 @@
+/*
+ * Copyright OpenEmbedded Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#pragma once
+
+#include <string>
+
+struct CppExample
+{
+    inline static const std::string test_string = "cpp-example-lib Magic: 123456789";
+
+    /* Retrieve a constant string */
+    const std::string &get_string();
+    /* Retrieve a constant string from a library */
+    const char *get_json_c_version();
+    /* Call a more advanced function from a library */
+    void print_json();
+};

meta-selftest/recipes-test/cpp/files/cpp-example.cpp

@@ -0,0 +1,18 @@
+/*
+ * Copyright OpenEmbedded Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include "cpp-example-lib.hpp"
+
+#include <iostream>
+
+int main()
+{
+    auto cpp_example = CppExample();
+    std::cout << "C++ example linking " << cpp_example.get_string() << std::endl;
+    std::cout << "Linking json-c version " << cpp_example.get_json_c_version() << std::endl;
+    cpp_example.print_json();
+    return 0;
+}

meta-selftest/recipes-test/cpp/files/meson.build

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+#
+# Copyright OpenEmbedded Contributors
+#
+# SPDX-License-Identifier: MIT
+#
+
+project('meson-example', 'cpp',
+    version: '1.0.0',
+    default_options: ['cpp_std=c++17']
+    )
+
+jsoncdep = dependency('json-c')
+
+if get_option('FAILING_TEST').enabled()
+    add_project_arguments('-DFAIL_COMPARISON_STR=foo', language: 'cpp')
+endif
+
+mesonexlib = shared_library('mesonexlib',
+    'cpp-example-lib.cpp', 'cpp-example-lib.hpp',
+	version: meson.project_version(),
+	soversion: meson.project_version().split('.')[0],
+    dependencies : jsoncdep,
+    install : true
+    )
+
+executable('mesonex',
+    'cpp-example.cpp',
+    link_with : mesonexlib,
+    install : true
+    )
+
+test_mesonex = executable('test-mesonex',
+    'test-cpp-example.cpp',
+    link_with : mesonexlib,
+    install : true
+)
+
+test('meson example test', test_mesonex)

meta-selftest/recipes-test/cpp/files/meson.options

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+
+option('FAILING_TEST', type : 'feature', value : 'disabled',
+    description : 'Compile a failing unit test to test the test infrastructure')

meta-selftest/recipes-test/cpp/files/test-cpp-example.cpp

@@ -0,0 +1,25 @@
+/*
+* Copyright OpenEmbedded Contributors
+*
+* SPDX-License-Identifier: MIT
+*/
+
+#include "cpp-example-lib.hpp"
+
+#include <iostream>
+
+/* This is for creating a failing test for testing the test infrastructure */
+#ifndef FAIL_COMPARISON_STR
+#define FAIL_COMPARISON_STR ""
+#endif
+
+int main() {
+    auto cpp_example = CppExample();
+    auto ret_string = cpp_example.get_string();
+    if(0 == ret_string.compare(CppExample::test_string + FAIL_COMPARISON_STR)) {
+        std::cout << "PASS: " << ret_string << " = " << CppExample::test_string << std::endl;
+    } else {
+        std::cout << "FAIL: " << ret_string << " != " << CppExample::test_string << std::endl;
+        return 1;
+    }
+}

meta-selftest/recipes-test/cpp/meson-example.bb

@@ -0,0 +1,27 @@
+#
+# Copyright OpenEmbedded Contributors
+#
+# SPDX-License-Identifier: MIT
+#
+
+SUMMARY = "A C++ example compiled with meson."
+
+require cpp-example.inc
+
+SRC_URI += "\
+    file://meson.build \
+    file://meson.options \
+"
+
+inherit pkgconfig meson
+
+PACKAGECONFIG[failing_test] = "-DFAILING_TEST=enabled"
+
+FILES:${PN}-ptest += "${bindir}/test-mesonex"
+
+do_run_tests () {
+    meson test -C "${B}" --no-rebuild
+}
+do_run_tests[doc] = "Run meson test using qemu-user"
+
+addtask do_run_tests after do_compile

meta-selftest/recipes-test/cpp/meson-example/run-ptest

@@ -0,0 +1,10 @@
+#!/bin/sh
+#
+# Copyright OpenEmbedded Contributors
+#
+# SPDX-License-Identifier: MIT
+#
+
+test-mesonex
+
+# Note: run-ptests exits with exit value from test-mesonex