[libretiny] Keep zero-size allocations from hanging the LN882x

esphome/components/libretiny/__init__.py

@@ -32,6 +32,7 @@ from esphome.storage_json import StorageJSON
 from . import gpio  # noqa: F401
 from .const import (
     COMPONENT_BK72XX,
+    COMPONENT_LN882X,
     CONF_GPIO_RECOVER,
     CONF_LOGLEVEL,
     CONF_SDK_SILENT,
@@ -490,6 +491,12 @@ async def component_to_code(config):
         # Not enabled on RTL87xx/LN882x — costs more heap than it saves there.
         cg.add_build_flag("-DconfigSUPPORT_STATIC_ALLOCATION=1")
 
+    # LN882x: route FreeRTOS allocations through ln882x_zero_malloc.c, which
+    # turns a zero-size request into one byte so it cannot trip the SDK's
+    # malloc-failed hook (an LN_ASSERT spin until the watchdog resets).
+    if config[CONF_COMPONENT_ID] == COMPONENT_LN882X:
+        cg.add_build_flag("-Wl,--wrap=pvPortMalloc")
+
     # RTL8710B needs FreeRTOS 8.2.3+ for xTaskNotifyGive/ulTaskNotifyTake
     # required by AsyncTCP 3.4.3+ (https://github.com/esphome/esphome/issues/10220)
     # RTL8720C (ambz2) requires FreeRTOS 10.x so this only applies to RTL8710B

esphome/components/libretiny/ln882x_zero_malloc.c

@@ -0,0 +1,27 @@
+/*
+ * LN882x: never ask the FreeRTOS heap for zero bytes.
+ *
+ * The LN882H SDK builds FreeRTOS with configUSE_MALLOC_FAILED_HOOK, and its
+ * hook (components/kernel/FreeRTOS/hooks.c) ends in LN_ASSERT(0), which spins
+ * until the watchdog resets the chip. heap_5 returns NULL for a zero-size
+ * request, so a harmless malloc(0) runs that hook. LibreTiny's scan handler
+ * makes exactly that request when a scan finds no networks, which is what
+ * happens right after an access point drops the device: the chip hangs and
+ * resets about ten seconds later.
+ *
+ * Linked with -Wl,--wrap=pvPortMalloc for LN882x only, so every caller,
+ * LibreTiny's malloc wrappers included, goes through here. Drop this once
+ * LibreTiny stops allocating zero entries in its LN882H scan handler.
+ */
+
+#ifdef USE_LN882X
+
+#include <stddef.h>
+
+void *__real_pvPortMalloc(size_t size);  // NOLINT(readability-identifier-naming)
+
+void *__wrap_pvPortMalloc(size_t size) {  // NOLINT(readability-identifier-naming)
+  return __real_pvPortMalloc(size == 0 ? 1 : size);
+}
+
+#endif  // USE_LN882X