diff --git a/include/zephyr/device.h b/include/zephyr/device.h
index 2862c0befd38b4..e8bbc09a2990f2 100644
--- a/include/zephyr/device.h
+++ b/include/zephyr/device.h
@@ -1020,13 +1020,24 @@ device_get_dt_nodelabels(const struct device *dev)
 		.state = (state_),							\
 		.data = (data_),							\
 		IF_ENABLED(CONFIG_DEVICE_DEPS, (.deps = (deps_),)) /**/			\
-		IF_ENABLED(CONFIG_PM_DEVICE, ({ .pm_base = (pm_),},)) /**/		\
+		IF_ENABLED(CONFIG_PM_DEVICE, Z_DEVICE_INIT_PM_BASE(pm_)) /**/		\
 		IF_ENABLED(CONFIG_DEVICE_DT_METADATA,					\
 			   (IF_ENABLED(DT_NODE_EXISTS(node_id_),			\
 				       (.dt_meta = &Z_DEVICE_DT_METADATA_NAME_GET(	\
 						dev_id_),))))				\
 	}
 
+/*
+ * Anonymous unions require C11. Some pre-C11 gcc versions have early support for anonymous
+ * unions but they require these braces when combined with C99 designated initializers. For
+ * more details see https://docs.zephyrproject.org/latest/develop/languages/cpp/
+ */
+#if defined(__STDC_VERSION__) && (__STDC_VERSION__) < 201100
+#  define Z_DEVICE_INIT_PM_BASE(pm_) ({ .pm_base = (pm_),},)
+#else
+#  define Z_DEVICE_INIT_PM_BASE(pm_)   (.pm_base = (pm_),)
+#endif
+
 /**
  * @brief Device section name (used for sorting purposes).
  *
@@ -1098,10 +1109,7 @@ device_get_dt_nodelabels(const struct device *dev)
 		Z_INIT_ENTRY_NAME(DEVICE_NAME_GET(dev_id)) = {                                     \
 			.init_fn = {COND_CODE_1(Z_DEVICE_IS_MUTABLE(node_id), (.dev_rw), (.dev)) = \
 					    (init_fn_)},                                           \
-			{                                                                          \
-				COND_CODE_1(Z_DEVICE_IS_MUTABLE(node_id), (.dev_rw), (.dev)) =     \
-					&DEVICE_NAME_GET(dev_id),                                  \
-			},                                                                         \
+			Z_DEVICE_INIT_ENTRY_DEV(node_id, dev_id),                                  \
 	}
 
 #define Z_DEFER_DEVICE_INIT_ENTRY_DEFINE(node_id, dev_id, init_fn_)                                \
@@ -1110,12 +1118,23 @@ device_get_dt_nodelabels(const struct device *dev)
 		Z_INIT_ENTRY_NAME(DEVICE_NAME_GET(dev_id)) = {                                     \
 			.init_fn = {COND_CODE_1(Z_DEVICE_IS_MUTABLE(node_id), (.dev_rw), (.dev)) = \
 					    (init_fn_)},                                           \
-			{                                                                          \
-				COND_CODE_1(Z_DEVICE_IS_MUTABLE(node_id), (.dev_rw), (.dev)) =     \
-					&DEVICE_NAME_GET(dev_id),                                  \
-			},                                                                         \
+			Z_DEVICE_INIT_ENTRY_DEV(node_id, dev_id),                                  \
 	}
 
+/*
+ * Anonymous unions require C11. Some pre-C11 gcc versions have early support for anonymous
+ * unions but they require these braces when combined with C99 designated initializers. For
+ * more details see https://docs.zephyrproject.org/latest/develop/languages/cpp/
+ */
+#if defined(__STDC_VERSION__) && (__STDC_VERSION__) < 201100
+#  define Z_DEVICE_INIT_ENTRY_DEV(node_id, dev_id) { Z_DEV_ENTRY_DEV(node_id, dev_id) }
+#else
+#  define Z_DEVICE_INIT_ENTRY_DEV(node_id, dev_id)   Z_DEV_ENTRY_DEV(node_id, dev_id)
+#endif
+
+#define Z_DEV_ENTRY_DEV(node_id, dev_id)                                                           \
+	COND_CODE_1(Z_DEVICE_IS_MUTABLE(node_id), (.dev_rw), (.dev)) =  &DEVICE_NAME_GET(dev_id)
+
 /**
  * @brief Define a @ref device and all other required objects.
  *
diff --git a/include/zephyr/pm/device.h b/include/zephyr/pm/device.h
index ce0e53d7446f05..5d3b4a96cea7bc 100644
--- a/include/zephyr/pm/device.h
+++ b/include/zephyr/pm/device.h
@@ -242,9 +242,9 @@ BUILD_ASSERT(offsetof(struct pm_device_isr, base) == 0);
  */
 #define Z_PM_DEVICE_BASE_INIT(obj, node_id, pm_action_cb, _flags)	     \
 	{								     \
-		.action_cb = pm_action_cb,				     \
-		.state = PM_DEVICE_STATE_ACTIVE,			     \
 		.flags = ATOMIC_INIT(Z_PM_DEVICE_FLAGS(node_id) | (_flags)), \
+		.state = PM_DEVICE_STATE_ACTIVE,			     \
+		.action_cb = pm_action_cb,				     \
 		Z_PM_DEVICE_POWER_DOMAIN_INIT(node_id)			     \
 	}
 
diff --git a/tests/lib/cpp/cxx/app.overlay b/tests/lib/cpp/cxx/app.overlay
new file mode 100644
index 00000000000000..69b87b4c7ac752
--- /dev/null
+++ b/tests/lib/cpp/cxx/app.overlay
@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2024 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Application overlay for creating a fake device instance we can use to
+ * test. Subset of tests/kernel/device/app.overlay and other app.overlay
+ * files.
+ */
+
+/ {
+	test_dev0_boot: dev0 {
+		compatible = "fake-cpp-driver";
+		status = "okay";
+	};
+
+	test_dev1_dfr: dev1 {
+		compatible = "fake-cpp-driver";
+		status = "okay";
+
+		zephyr,deferred-init;
+	};
+};
diff --git a/tests/lib/cpp/cxx/dts/bindings/test-device.yaml b/tests/lib/cpp/cxx/dts/bindings/test-device.yaml
new file mode 100644
index 00000000000000..154c9b54f82131
--- /dev/null
+++ b/tests/lib/cpp/cxx/dts/bindings/test-device.yaml
@@ -0,0 +1,11 @@
+# Copyright (c) 2024, Intel Corporation
+# SPDX-License-Identifier: Apache-2.0
+
+include: [base.yaml]
+
+description: |
+    When this file is missing _or_ the include above is missing, then
+    test coverage is _quietly_ reduced! Code that should fail turns
+    green. Nasty.
+
+compatible: "fake-cpp-driver"
diff --git a/tests/lib/cpp/cxx/prj.conf b/tests/lib/cpp/cxx/prj.conf
index 15ae9ce1ebd490..22fcfc3b59afa5 100644
--- a/tests/lib/cpp/cxx/prj.conf
+++ b/tests/lib/cpp/cxx/prj.conf
@@ -5,8 +5,22 @@ CONFIG_ZTEST_STACK_SIZE=2048
 CONFIG_COMMON_LIBC_MALLOC_ARENA_SIZE=128
 CONFIG_CRC=y
 
+# Enable optional features that are off by default to cover as much as
+# possible of the same .h files. Ideally, kconfiglib.py would support
+# "randconfig" because turning on some options can also reduce test
+# coverage in some areas. But: 1. combinatorial explosion, 2. it does
+# not.
+
 # RTIO
 CONFIG_RTIO=y
 CONFIG_RTIO_SUBMIT_SEM=y
 CONFIG_RTIO_CONSUME_SEM=y
 CONFIG_RTIO_SYS_MEM_BLOCKS=y
+
+# Enable more features and C++ coverage in device.h, pm/device.h, pm.h...
+CONFIG_PM=y
+CONFIG_PM_DEVICE=y
+CONFIG_PM_DEVICE_RUNTIME=y
+CONFIG_DEVICE_DT_METADATA=y
+# Deprecated but on by default! Silence the warning:
+CONFIG_PM_DEVICE_RUNTIME_EXCLUSIVE=n
diff --git a/tests/lib/cpp/cxx/src/main.cpp b/tests/lib/cpp/cxx/src/main.cpp
index b8b77c6c26a5a7..8b149290bab657 100644
--- a/tests/lib/cpp/cxx/src/main.cpp
+++ b/tests/lib/cpp/cxx/src/main.cpp
@@ -15,6 +15,7 @@
 
 #include <zephyr/init.h>
 #include <zephyr/device.h>
+#include <zephyr/pm/device.h>
 #include <zephyr/kernel.h>
 #include <zephyr/net/buf.h>
 #include <zephyr/sys/crc.h>
@@ -136,3 +137,18 @@ ZTEST(cxx_tests, test_new_delete)
 	delete test_foo;
 }
 ZTEST_SUITE(cxx_tests, NULL, NULL, NULL, NULL, NULL);
+
+/*
+ * Unused macros are parsed but not actually compiled. So, even with all their NULL
+ * arguments these one-liners add significant C++ coverage. For instance this actually
+ * compiles some of the macros in zephyr/device.h in C++.
+ *
+ * DEVICE_DEFINE(dev_id, name, * init_fn, pm, data, config, level, prio, api)
+ */
+DEVICE_DT_DEFINE(DT_NODELABEL(test_dev0_boot), NULL, NULL, NULL, NULL, POST_KERNEL, 33, NULL);
+
+DEVICE_DT_DEFINE(DT_NODELABEL(test_dev1_dfr), NULL, NULL, NULL, NULL, POST_KERNEL, 33, NULL);
+
+static int fake_pm_action(const struct device *dev,
+		enum pm_device_action pm_action) { return -1; }
+PM_DEVICE_DT_DEFINE(DT_NODELABEL(test_dev0_boot), fake_pm_action);