[core] Use placement new allocation for Pvariables (#15079)

Co-authored-by: J. Nick Koston <nick@home-assistant.io>
Co-authored-by: J. Nick Koston <nick@koston.org>

esphome/cpp_generator.py

@@ -579,10 +579,41 @@ def Pvariable(id_: ID, rhs: SafeExpType, type_: "MockObj" = None) -> "MockObj":
     obj = MockObj(id_, "->")
     if type_ is not None:
         id_.type = type_
-    decl = VariableDeclarationExpression(id_.type, "*", id_, static=True)
-    CORE.add_global(decl)
-    assignment = AssignmentExpression(None, None, id_, rhs)
-    CORE.add(assignment)
+
+    if isinstance(rhs, MockObj) and rhs.is_new_expr:
+        # For 'new' allocations, use placement new into static storage
+        # to avoid heap fragmentation on embedded devices.
+        the_type = id_.type
+        storage_name = f"{id_.id}__pstorage"
+
+        # Declare aligned byte array for the object storage
+        CORE.add_global(
+            RawStatement(
+                f"alignas({the_type}) static unsigned char {storage_name}[sizeof({the_type})];"
+            )
+        )
+        CORE.add_global(
+            AssignmentExpression(
+                f"static {the_type}",
+                "*const ",
+                id_,
+                MockObj(f"reinterpret_cast<{the_type} *>({storage_name})"),
+            )
+        )
+        # Extract args from the CallExpression and rebuild as placement new.
+        # Template args are already encoded in the_type (e.g. GlobalsComponent<int>),
+        # so we only pass the constructor args, not template_args.
+        call_expr = rhs.base
+        assert isinstance(call_expr, CallExpression), (
+            f"Expected CallExpression for placement new, got {type(call_expr)}"
+        )
+        placement_new = CallExpression(f"new({id_.id}) {the_type}", *call_expr.args)
+        CORE.add(ExpressionStatement(placement_new))
+    else:
+        decl = VariableDeclarationExpression(id_.type, "*", id_, static=True)
+        CORE.add_global(decl)
+        CORE.add(AssignmentExpression(None, None, id_, rhs))
+
     CORE.register_variable(id_, obj)
     return obj
 
@@ -799,11 +830,12 @@ class MockObj(Expression):
     Mostly consists of magic methods that allow ESPHome's codegen syntax.
     """
 
-    __slots__ = ("base", "op")
+    __slots__ = ("base", "op", "is_new_expr")
 
-    def __init__(self, base, op="."):
+    def __init__(self, base, op=".", is_new_expr=False) -> None:
         self.base = base
         self.op = op
+        self.is_new_expr = is_new_expr
 
     def __getattr__(self, attr: str) -> "MockObj":
         # prevent python dunder methods being replaced by mock objects
@@ -818,7 +850,7 @@ class MockObj(Expression):
 
     def __call__(self, *args: SafeExpType) -> "MockObj":
         call = CallExpression(self.base, *args)
-        return MockObj(call, self.op)
+        return MockObj(call, self.op, is_new_expr=self.is_new_expr)
 
     def __str__(self):
         return str(self.base)
@@ -832,7 +864,7 @@ class MockObj(Expression):
 
     @property
     def new(self) -> "MockObj":
-        return MockObj(f"new {self.base}", "->")
+        return MockObj(f"new {self.base}", "->", is_new_expr=True)
 
     def template(self, *args: SafeExpType) -> "MockObj":
         """Apply template parameters to this object."""

tests/component_tests/binary_sensor/test_binary_sensor.py

@@ -15,7 +15,7 @@ def test_binary_sensor_is_setup(generate_main):
     )
 
     # Then
-    assert "new gpio::GPIOBinarySensor();" in main_cpp
+    assert "static gpio::GPIOBinarySensor *const" in main_cpp
     assert "App.register_binary_sensor" in main_cpp
 
 

tests/component_tests/button/test_button.py

@@ -13,7 +13,8 @@ def test_button_is_setup(generate_main):
     main_cpp = generate_main("tests/component_tests/button/test_button.yaml")
 
     # Then
-    assert "new wake_on_lan::WakeOnLanButton();" in main_cpp
+    assert "static wake_on_lan::WakeOnLanButton *const" in main_cpp
+    assert ") wake_on_lan::WakeOnLanButton();" in main_cpp
     assert "App.register_button" in main_cpp
     assert "App.register_component" in main_cpp
 

tests/component_tests/conftest.py

@@ -134,7 +134,7 @@ def generate_main() -> Generator[Callable[[str | Path], str]]:
         CORE.config_path = Path(path)
         CORE.config = read_config({})
         generate_cpp_contents(CORE.config)
-        return CORE.cpp_main_section
+        return CORE.cpp_global_section + CORE.cpp_main_section
 
     yield generator
 

tests/component_tests/deep_sleep/test_deep_sleep.py

@@ -7,7 +7,11 @@ def test_deep_sleep_setup(generate_main):
     """
     main_cpp = generate_main("tests/component_tests/deep_sleep/test_deep_sleep1.yaml")
 
-    assert "deepsleep = new deep_sleep::DeepSleepComponent();" in main_cpp
+    assert (
+        "static deep_sleep::DeepSleepComponent *const deepsleep = reinterpret_cast<deep_sleep::DeepSleepComponent *>(deepsleep__pstorage);"
+        in main_cpp
+    )
+    assert "new(deepsleep) deep_sleep::DeepSleepComponent();" in main_cpp
     assert "App.register_component_(deepsleep);" in main_cpp
 
 

tests/component_tests/globals/config/globals_test.yaml

@@ -0,0 +1,16 @@
+esphome:
+  name: test
+
+esp32:
+  board: esp32dev
+
+globals:
+  - id: my_global_int
+    type: int
+    initial_value: "42"
+  - id: my_global_float
+    type: float
+    initial_value: "1.5"
+  - id: my_global_bool
+    type: bool
+    initial_value: "true"

tests/component_tests/globals/test_globals.py

@@ -0,0 +1,27 @@
+"""Tests for the globals component."""
+
+from __future__ import annotations
+
+from collections.abc import Callable
+from pathlib import Path
+
+
+def test_globals_placement_new_with_template_args(
+    generate_main: Callable[[str | Path], str],
+    component_config_path: Callable[[str], Path],
+) -> None:
+    """Test that globals uses placement new with template arguments preserved."""
+    main_cpp = generate_main(component_config_path("globals_test.yaml"))
+
+    # Globals uses Pvariable with Type.new(template_args, initial_value)
+    # which exercises the template_args preservation in placement new.
+    assert "static globals::GlobalsComponent<int> *const my_global_int" in main_cpp
+    assert "sizeof(globals::GlobalsComponent<int>)" in main_cpp
+    assert "new(my_global_int) globals::GlobalsComponent<int>" in main_cpp
+
+    # Verify initial value is passed as constructor arg
+    assert "42" in main_cpp
+
+    # Check other globals are also generated
+    assert "sizeof(globals::GlobalsComponent<float>)" in main_cpp
+    assert "sizeof(globals::GlobalsComponent<bool>)" in main_cpp

tests/component_tests/gpio/test_gpio_binary_sensor.py

@@ -16,7 +16,8 @@ def test_gpio_binary_sensor_basic_setup(
     """
     main_cpp = generate_main("tests/component_tests/gpio/test_gpio_binary_sensor.yaml")
 
-    assert "new gpio::GPIOBinarySensor();" in main_cpp
+    assert "static gpio::GPIOBinarySensor *const" in main_cpp
+    assert ") gpio::GPIOBinarySensor();" in main_cpp
     assert "App.register_binary_sensor" in main_cpp
     # set_use_interrupt(true) should NOT be generated (uses C++ default)
     assert "bs_gpio->set_use_interrupt(true);" not in main_cpp

tests/component_tests/image/test_init.py

@@ -242,7 +242,15 @@ def test_image_generation(
     main_cpp = generate_main(component_config_path("image_test.yaml"))
     assert "uint8_t_id[] PROGMEM = {0x24, 0x21, 0x24, 0x21" in main_cpp
     assert (
-        "cat_img = new image::Image(uint8_t_id, 32, 24, image::IMAGE_TYPE_RGB565, image::TRANSPARENCY_OPAQUE);"
+        "alignas(image::Image) static unsigned char cat_img__pstorage[sizeof(image::Image)];"
+        in main_cpp
+    )
+    assert (
+        "static image::Image *const cat_img = reinterpret_cast<image::Image *>(cat_img__pstorage);"
+        in main_cpp
+    )
+    assert (
+        "new(cat_img) image::Image(uint8_t_id, 32, 24, image::IMAGE_TYPE_RGB565, image::TRANSPARENCY_OPAQUE);"
         in main_cpp
     )
 

tests/component_tests/logger/test_logger.py

@@ -22,6 +22,10 @@ def test_logger_pre_setup_before_other_components(generate_main):
 
     # Find all "new " allocations (component creation)
     new_allocations = list(re.finditer(r"\bnew [\w:]+", main_cpp))
+    # Find all "new(" allocations (component creation) and combine them
+    new_allocations.extend(re.finditer(r"\bnew\([^)]+\) [\w:]+", main_cpp))
+    # Sort allocations by position in the file
+    new_allocations.sort(key=lambda m: m.start())
     assert len(new_allocations) > 0, "No component allocations found"
 
     # Separate logger and non-logger allocations

tests/component_tests/mipi_dsi/test_mipi_dsi_config.py

@@ -119,7 +119,15 @@ def test_code_generation(
 
     main_cpp = generate_main(component_fixture_path("mipi_dsi.yaml"))
     assert (
-        "p4_nano = new mipi_dsi::MIPI_DSI(800, 1280, display::COLOR_BITNESS_565, 16);"
+        "alignas(mipi_dsi::MIPI_DSI) static unsigned char p4_nano__pstorage[sizeof(mipi_dsi::MIPI_DSI)];"
+        in main_cpp
+    )
+    assert (
+        "static mipi_dsi::MIPI_DSI *const p4_nano = reinterpret_cast<mipi_dsi::MIPI_DSI *>(p4_nano__pstorage);"
+        in main_cpp
+    )
+    assert (
+        "new(p4_nano) mipi_dsi::MIPI_DSI(800, 1280, display::COLOR_BITNESS_565, 16);"
         in main_cpp
     )
     assert "set_init_sequence({224, 1, 0, 225, 1, 147, 226, 1," in main_cpp

tests/component_tests/status_led/config/status_led_test.yaml

@@ -0,0 +1,8 @@
+esphome:
+  name: test
+
+esp32:
+  board: esp32dev
+
+status_led:
+  pin: GPIO2

tests/component_tests/status_led/test_status_led.py

@@ -0,0 +1,23 @@
+"""Tests for status_led."""
+
+from __future__ import annotations
+
+from collections.abc import Callable
+from pathlib import Path
+
+
+def test_status_led_generation(
+    generate_main: Callable[[str | Path], str],
+    component_config_path: Callable[[str], Path],
+) -> None:
+    """Test status_led generation."""
+    main_cpp = generate_main(component_config_path("status_led_test.yaml"))
+    assert (
+        "alignas(status_led::StatusLED) static unsigned char status_led_statusled_id__pstorage[sizeof(status_led::StatusLED)];"
+        in main_cpp
+    )
+    assert (
+        "static status_led::StatusLED *const status_led_statusled_id = reinterpret_cast<status_led::StatusLED *>(status_led_statusled_id__pstorage);"
+        in main_cpp
+    )
+    assert "new(status_led_statusled_id) status_led::StatusLED(" in main_cpp

tests/component_tests/text/test_text.py

@@ -13,7 +13,8 @@ def test_text_is_setup(generate_main):
     main_cpp = generate_main("tests/component_tests/text/test_text.yaml")
 
     # Then
-    assert "new template_::TemplateText();" in main_cpp
+    assert "static template_::TemplateText *const" in main_cpp
+    assert ") template_::TemplateText();" in main_cpp
     assert "App.register_text" in main_cpp
 
 

tests/component_tests/text_sensor/test_text_sensor.py

@@ -13,7 +13,8 @@ def test_text_sensor_is_setup(generate_main):
     main_cpp = generate_main("tests/component_tests/text_sensor/test_text_sensor.yaml")
 
     # Then
-    assert "new template_::TemplateTextSensor();" in main_cpp
+    assert "static template_::TemplateTextSensor *const" in main_cpp
+    assert ") template_::TemplateTextSensor();" in main_cpp
     assert "App.register_text_sensor" in main_cpp