Merge pull request #20363 from mguetschow/malloc-monitor

Monitoring malloc usage

makefiles/pseudomodules.inc.mk

@@ -259,7 +259,11 @@ PSEUDOMODULES += libc_gettimeofday
 ## @defgroup pseudomodule_malloc_tracing malloc_tracing
 ## @brief Debug dynamic memory management by hooking in a print into each call
 ##        of malloc(), calloc(), realloc() and free
+## @{
+## @deprecated  Use module `malloc_monitor` with verbous configuration instead;
+##              will be removed after 2024.07 release.
 PSEUDOMODULES += malloc_tracing
+## @}
 
 ## @defgroup pseudomodule_mpu_stack_guard mpu_stack_guard
 ## @brief MPU based stack guard

sys/Kconfig

@@ -79,6 +79,7 @@ rsource "evtimer/Kconfig"
 rsource "log_color/Kconfig"
 rsource "log_printfnoformat/Kconfig"
 rsource "luid/Kconfig"
+rsource "malloc_monitor/Kconfig"
 rsource "malloc_thread_safe/Kconfig"
 rsource "matstat/Kconfig"
 rsource "memarray/Kconfig"

sys/include/malloc_monitor.h

@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2024 TU Dresden
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+/**
+ * @ingroup     sys_malloc_monitor
+ * @{
+ */
+
+#ifndef MALLOC_MONITOR_H
+#define MALLOC_MONITOR_H
+
+#include <assert.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <string.h>
+
+#include "architecture.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Obtain current heap memory usage.
+ *
+ * @return      current heap memory usage in bytes
+ */
+size_t malloc_monitor_get_usage_current(void);
+
+/**
+ * @brief Obtain maximum heap memory usage since last call to
+ *        @ref malloc_monitor_reset_high_watermark().
+ *
+ * @return      maximum heap memory usage in bytes
+ */
+size_t malloc_monitor_get_usage_high_watermark(void);
+
+/**
+ * @brief Reset maximum heap memory usage.
+ *
+ * After calling this function, @ref malloc_monitor_get_usage_high_watermark()
+ * will return @ref malloc_monitor_get_usage_current() until further changes
+ * to heap memory usage.
+ */
+void malloc_monitor_reset_high_watermark(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* MALLOC_MONITOR_H */
+
+/**
+ * @}
+ */

sys/include/malloc_monitor_internal.h

@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2024 TU Dresden
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+/**
+ * @defgroup    sys_malloc_monitor_internals Heap Memory Usage Monitor internals
+ * @ingroup     sys_malloc_monitor
+ * @{
+ *
+ * @brief       internals for monitoring heap memory usage (calls to malloc/calloc/realloc/free)
+ * @author      Mikolai Gütschow <mikolai.guetschow@tu-dresden.de>
+ */
+
+#ifndef MALLOC_MONITOR_INTERNAL_H
+#define MALLOC_MONITOR_INTERNAL_H
+
+#include <assert.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <string.h>
+
+#include "architecture.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Record malloc/calloc/realloc call increasing heap usage.
+ *
+ * @param[in]   ptr         pointer to newly allocated memory
+ * @param[in]   size        size of newly allocated memory
+ * @param[in]   pc          PC of calling function
+ * @param[in]   func_prefix prefix identifying memory function, one of "m","c","re"
+ *
+ * @internal
+ */
+void malloc_monitor_add(void *ptr, size_t size, uinttxtptr_t pc, char *func_prefix);
+
+/**
+ * @brief Record free/realloc call decreasing heap usage.
+ *
+ * @param[in]   ptr    pointer to memory that is being freed
+ * @param[in]   pc     PC of calling function
+ *
+ * @internal
+ */
+void malloc_monitor_rm(void *ptr, uinttxtptr_t pc);
+
+/**
+ * @brief Record realloc call either increasing or decreasing heap usage.
+ *
+ * @param[in]   ptr_old     pointer to previously allocated memory
+ * @param[in]   ptr_new     pointer to newly allocated memory
+ * @param[in]   size_new    size of newly allocated memory
+ * @param[in]   pc          PC of calling function
+ *
+ * @internal
+ */
+void malloc_monitor_mv(void *ptr_old, void *ptr_new, size_t size_new, uinttxtptr_t pc);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* MALLOC_MONITOR_INTERNAL_H */
+
+/**
+ * @}
+ */

sys/malloc_monitor/Kconfig

@@ -0,0 +1,23 @@
+# Copyright (C) 2024 TU Dresden
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+#
+
+menuconfig MODULE_SYS_MALLOC_MONITOR
+    bool "Heap Memory Usage Monitor"
+
+config MODULE_SYS_MALLOC_MONITOR_SIZE
+    int "Monitor Size"
+    default 100
+    depends on MODULE_SYS_MALLOC_MONITOR
+    help
+        Specifies maximum number of pointers that can be monitored at once.
+
+config MODULE_SYS_MALLOC_MONITOR_VERBOSE
+    bool "Verbose"
+    default false
+    depends on MODULE_SYS_MALLOC_MONITOR
+    help
+        Print detailed log of calls to malloc/realloc/free

sys/malloc_monitor/Makefile

@@ -0,0 +1 @@
+include $(RIOTBASE)/Makefile.base

sys/malloc_monitor/Makefile.dep

@@ -0,0 +1 @@
+USEMODULE += malloc_thread_safe

sys/malloc_monitor/doc.txt

@@ -0,0 +1,72 @@
+/**
+ * @defgroup   sys_malloc_monitor Heap Memory Usage Monitor
+ * @ingroup    sys_memory_management
+ * @brief      This module allows to monitor the dynamic memory usage of a certain piece of code.
+ * @warning    This module automatically selects @ref sys_malloc_ts and naturally
+ *             incurs a certain runtime overhead. It is not meant for production usage.
+ * @author      Mikolai Gütschow <mikolai.guetschow@tu-dresden.de>
+ *
+ * # Description
+ *
+ * This module allows to monitor the dynamic memory usage of a certain piece of code.
+ * It works by hooking into (wrappers to) @ref malloc(), @ref calloc(), @ref realloc(),
+ * and @ref free() calls to internally record the current and all-time maximum heap memory usage.
+ *
+ * Note that in general dynamic memory management is a bad idea on the constrained devices RIOT
+ * is targeting. So maybe it is better to just adapt your code to use static memory management instead.
+ *
+ * # Usage
+ *
+ * Enable the module with `USEMODULE += malloc_monitor`.
+ *
+ * Add `#include "malloc_monitor.h"` to the file in which you want to monitor dynamic memory usage.
+ * Use @ref malloc_monitor_get_usage_current() to retrieve the size of the currently allocated
+ * heap memory in bytes. @ref malloc_monitor_get_usage_high_watermark() returns the all-time maximum
+ * since startup or the last call to  @ref malloc_monitor_reset_high_watermark().
+ *
+ * Note that `malloc_monitor` currently has no notion of threads and will at any point in time report
+ * the global dynamic memory usage, not the one used by the currently running thread.
+ * Thread-safety is achieved through usage of @ref sys_malloc_ts, though.
+ *
+ * ## Example
+ *
+ * Imagine you want to investigate the dynamic memory consumption of a certain function `func()`.
+ * The following snippet could get you started:
+ *
+ * ```c
+ * #include <stddef.h>
+ * #include <stdio.h>
+ *
+ * #include "malloc_monitor.h"
+ *
+ * int main(void)
+ * {
+ *     size_t before = malloc_monitor_get_usage_current();
+ *     size_t before_max = malloc_monitor_get_usage_high_watermark();
+ *     func();
+ *     size_t after = malloc_monitor_get_usage_current();
+ *     size_t after_max = malloc_monitor_get_usage_high_watermark();
+ *
+ *     if (after != before) {
+ *         puts("func() " (after < before ? "decreased" : "increased") " global dynamic memory usage.");
+ *     }
+ *     printf("The maximal dynamic memory usage of func() was %d bytes.", after_max - before_max);
+ * }
+ * ```
+ *
+ * For further usage examples, refer to the corresponding tests in `tests/sys/malloc_monitor`.
+ *
+ * # Configuration
+ *
+ * The maximum number of pointers that can be monitored at once can be set with Kconfig
+ * in System > Heap Memory Usage Monitor > Monitor Size or by setting the corresponding
+ * CFlag in your application's Makefile as `CFLAGS += CONFIG_MODULE_SYS_MALLOC_MONITOR_SIZE=42`.
+ * It defaults to 100.
+ *
+ * For more fine-grained debugging of invalid calls to @ref free(), duplicated calls to @ref free(),
+ * or memory leaks, the module can be configured to print information on every call to @ref malloc(),
+ * @ref calloc(), @ref realloc(), or @ref free() by setting System > Heap Memory Usage Monitor > Verbose
+ * or adding `CFLAGS += CONFIG_MODULE_SYS_MALLOC_MONITOR_VERBOSE=1` to your Makefile.
+ * `malloc_monitor` defaults to be non-verbose.
+ *
+ */

sys/malloc_monitor/malloc_monitor.c

@@ -0,0 +1,170 @@
+/*
+ * Copyright (C) 2024 TU Dresden
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @{
+ *
+ * @file
+ * @brief   monitor heap memory usage (calls to malloc/realloc/free)
+ * @author  Mikolai Gütschow <mikolai.guetschow@tu-dresden.de>
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include "architecture.h"
+#include "assert.h"
+#include "cpu.h"
+#include "irq.h"
+#include "mutex.h"
+
+#include "malloc_monitor.h"
+#include "malloc_monitor_internal.h"
+
+#ifndef CONFIG_MODULE_SYS_MALLOC_MONITOR_SIZE
+#define CONFIG_MODULE_SYS_MALLOC_MONITOR_SIZE 100
+#endif
+
+#ifndef CONFIG_MODULE_SYS_MALLOC_MONITOR_VERBOSE
+#define CONFIG_MODULE_SYS_MALLOC_MONITOR_VERBOSE 0
+#endif
+
+static struct {
+    void *addr[CONFIG_MODULE_SYS_MALLOC_MONITOR_SIZE];
+    size_t size[CONFIG_MODULE_SYS_MALLOC_MONITOR_SIZE];
+    size_t current;
+    size_t high_watermark;
+} malloc_monitor = {
+    .addr = {NULL},
+    .current = 0,
+    .high_watermark = 0,
+};
+
+/* guards access to malloc_monitor */
+static mutex_t _lock;
+
+void malloc_monitor_add(void *ptr, size_t size, uinttxtptr_t pc, char *func_prefix)
+{
+    if (ptr == NULL) {
+        return;
+    }
+#if CONFIG_MODULE_SYS_MALLOC_MONITOR_VERBOSE
+    printf("%salloc(%" PRIuSIZE ") @ 0x%" PRIxTXTPTR " returned %p\n",
+        func_prefix, size, pc, ptr);
+#endif
+    assert(!irq_is_in());
+    mutex_lock(&_lock);
+    for (uint8_t i=0; i<CONFIG_MODULE_SYS_MALLOC_MONITOR_SIZE; i++) {
+        if (malloc_monitor.addr[i] == NULL) {
+            malloc_monitor.addr[i] = ptr;
+            malloc_monitor.size[i] = size;
+            malloc_monitor.current += size;
+            if (malloc_monitor.current > malloc_monitor.high_watermark) {
+                malloc_monitor.high_watermark = malloc_monitor.current;
+            }
+            mutex_unlock(&_lock);
+            return;
+        }
+    }
+    mutex_unlock(&_lock);
+    printf("malloc_monitor: maximum number of pointers to be monitored "
+        "(as set by CONFIG_MODULE_SYS_MALLOC_MONITOR_SIZE) exceeded.\n");
+    (void)func_prefix;
+    (void)pc;
+}
+
+void malloc_monitor_rm(void *ptr, uinttxtptr_t pc)
+{
+    if (ptr == NULL) {
+        return;
+    }
+#if CONFIG_MODULE_SYS_MALLOC_MONITOR_VERBOSE
+    printf("malloc_monitor: free(%p) @ 0x%" PRIxTXTPTR " \n", ptr, pc);
+#endif
+    assert(!irq_is_in());
+    mutex_lock(&_lock);
+    for (uint8_t i=0; i<CONFIG_MODULE_SYS_MALLOC_MONITOR_SIZE; i++) {
+        if (malloc_monitor.addr[i] == ptr) {
+            malloc_monitor.addr[i] = NULL;
+            malloc_monitor.current -= malloc_monitor.size[i];
+            mutex_unlock(&_lock);
+            return;
+        }
+    }
+    mutex_unlock(&_lock);
+    printf("malloc_monitor: free(%p) @ 0x%" PRIxTXTPTR " invalid\n", ptr, pc);
+}
+
+void malloc_monitor_mv(void *ptr_old, void *ptr_new, size_t size_new, uinttxtptr_t pc)
+{
+    if (ptr_old == NULL) {
+        malloc_monitor_add(ptr_new, size_new, pc, "re");
+        return;
+    }
+    if (size_new == 0) {
+        malloc_monitor_rm(ptr_old, pc);
+        return;
+    }
+    if (ptr_new == NULL) {
+        return;
+    }
+#if CONFIG_MODULE_SYS_MALLOC_MONITOR_VERBOSE
+    printf("malloc_monitor: realloc(%p, %" PRIuSIZE ") @0x%" PRIxTXTPTR " returned %p\n",
+        ptr_old, size_new, pc, ptr_new);
+#endif
+    assert(!irq_is_in());
+    mutex_lock(&_lock);
+    for (uint8_t i=0; i<CONFIG_MODULE_SYS_MALLOC_MONITOR_SIZE; i++) {
+        if (malloc_monitor.addr[i] == ptr_old) {
+            malloc_monitor.addr[i] = ptr_new;
+            size_t size_old = malloc_monitor.size[i];
+            malloc_monitor.size[i] = size_new;
+            if (size_new > size_old) {
+                malloc_monitor.current += size_new - size_old;
+                if (malloc_monitor.current > malloc_monitor.high_watermark) {
+                    malloc_monitor.high_watermark = malloc_monitor.current;
+                }
+            }
+            else {
+                malloc_monitor.current -= size_old - size_new;
+            }
+            mutex_unlock(&_lock);
+            return;
+        }
+    }
+    mutex_unlock(&_lock);
+    printf("malloc_monitor: realloc(%p) @ 0x%" PRIxTXTPTR " invalid\n", ptr_old, pc);
+}
+
+size_t malloc_monitor_get_usage_current(void)
+{
+    assert(!irq_is_in());
+    mutex_lock(&_lock);
+    size_t ret = malloc_monitor.current;
+    mutex_unlock(&_lock);
+    return ret;
+}
+
+size_t malloc_monitor_get_usage_high_watermark(void)
+{
+    assert(!irq_is_in());
+    mutex_lock(&_lock);
+    size_t ret = malloc_monitor.high_watermark;
+    mutex_unlock(&_lock);
+    return ret;
+}
+
+void malloc_monitor_reset_high_watermark(void)
+{
+    assert(!irq_is_in());
+    mutex_lock(&_lock);
+    malloc_monitor.high_watermark = malloc_monitor.current;
+    mutex_unlock(&_lock);
+}
+
+/** @} */

sys/malloc_thread_safe/doc.txt

@@ -1,6 +1,6 @@
 /**
 @defgroup   sys_malloc_ts           Thread-safe wrappers for malloc and friends
-@ingroup    sys
+@ingroup    sys_memory_management
 @brief      This module provides wrappers for malloc, calloc, realloc and free
             that provide mutually exclusive access to those functions.
 @warning    This module is automatically selected, if needed. Never add it

sys/malloc_thread_safe/malloc_wrappers.c

@@ -24,6 +24,7 @@
 #include "cpu.h"
 #include "irq.h"
 #include "kernel_defines.h"
+#include "malloc_monitor_internal.h"
 #include "mutex.h"
 
 extern void *__real_malloc(size_t size);
@@ -41,6 +42,9 @@ void __attribute__((used)) *__wrap_malloc(size_t size)
     assert(!irq_is_in());
     mutex_lock(&_lock);
     void *ptr = __real_malloc(size);
+    if (IS_USED(MODULE_MALLOC_MONITOR)) {
+        malloc_monitor_add(ptr, size, cpu_get_caller_pc(), "m");
+    }
     mutex_unlock(&_lock);
     if (IS_USED(MODULE_MALLOC_TRACING)) {
         printf("malloc(%" PRIuSIZE ") @ 0x%" PRIxTXTPTR " returned %p\n",
@@ -58,6 +62,9 @@ void __attribute__((used)) __wrap_free(void *ptr)
     assert(!irq_is_in());
     mutex_lock(&_lock);
     __real_free(ptr);
+    if (IS_USED(MODULE_MALLOC_MONITOR)) {
+        malloc_monitor_rm(ptr, cpu_get_caller_pc());
+    }
     mutex_unlock(&_lock);
 }
 
@@ -81,6 +88,9 @@ void * __attribute__((used)) __wrap_calloc(size_t nmemb, size_t size)
 
     mutex_lock(&_lock);
     void *res = __real_malloc(total_size);
+    if (IS_USED(MODULE_MALLOC_MONITOR)) {
+        malloc_monitor_add(res, total_size, cpu_get_caller_pc(), "c");
+    }
     mutex_unlock(&_lock);
     if (res) {
         memset(res, 0, total_size);
@@ -104,6 +114,9 @@ void * __attribute__((used))__wrap_realloc(void *ptr, size_t size)
     assert(!irq_is_in());
     mutex_lock(&_lock);
     void *new = __real_realloc(ptr, size);
+    if (IS_USED(MODULE_MALLOC_MONITOR)) {
+        malloc_monitor_mv(ptr, new, size, cpu_get_caller_pc());
+    }
     mutex_unlock(&_lock);
 
     if (IS_USED(MODULE_MALLOC_TRACING)) {

tests/sys/malloc_monitor/Makefile

@@ -0,0 +1,7 @@
+include ../Makefile.sys_common
+
+USEMODULE += embunit
+
+USEMODULE += malloc_monitor
+
+include $(RIOTBASE)/Makefile.include

tests/sys/malloc_monitor/Makefile.ci

@@ -0,0 +1,4 @@
+BOARD_INSUFFICIENT_MEMORY := \
+    atmega8 \
+    nucleo-l011k4 \
+    #

tests/sys/malloc_monitor/main.c

@@ -0,0 +1,212 @@
+/*
+ * Copyright (C) 2024 TU Dresden
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     tests
+ * @{
+ *
+ * @file
+ * @brief       Test application for MODULE_MALLOC_MONITOR
+ *
+ * @author      Mikolai Gütschow <mikolai.guetschow@tu-dresden.de>
+ * @}
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "embUnit.h"
+
+#include "malloc_monitor.h"
+
+#define MALLOC_SIZE 1
+
+#define TEST_MALLOC_MONITOR_SAVE \
+    size_t curr = malloc_monitor_get_usage_current(); \
+    size_t water = malloc_monitor_get_usage_high_watermark();
+
+#define TEST_ASSERT_CURRENT(num_alloc) TEST_ASSERT_EQUAL_INT(curr+num_alloc*MALLOC_SIZE, malloc_monitor_get_usage_current());
+#define TEST_ASSERT_WATERMARK(num_alloc) TEST_ASSERT_EQUAL_INT(water+num_alloc*MALLOC_SIZE, malloc_monitor_get_usage_high_watermark());
+
+/*
+ * malloc and free should be reflected by `malloc_monitor_get_usage_current()`.
+ * `malloc_monitor_get_usage_high_watermark()` should only be decreased on a call to
+ * `malloc_monitor_reset_high_watermark()`
+ */
+static void test_malloc_free(void)
+{
+    TEST_MALLOC_MONITOR_SAVE
+
+    TEST_ASSERT_CURRENT(0);
+    TEST_ASSERT_WATERMARK(0);
+
+    void *volatile alloc1 = malloc(MALLOC_SIZE);
+    TEST_ASSERT_NOT_NULL(alloc1);
+
+    TEST_ASSERT_CURRENT(1);
+    TEST_ASSERT_WATERMARK(1);
+
+    void *volatile alloc2 = malloc(MALLOC_SIZE);
+    TEST_ASSERT_NOT_NULL(alloc2);
+
+    TEST_ASSERT_CURRENT(2);
+    TEST_ASSERT_WATERMARK(2);
+
+    free(alloc1);
+
+    TEST_ASSERT_CURRENT(1);
+    TEST_ASSERT_WATERMARK(2);
+
+    malloc_monitor_reset_high_watermark();
+
+    TEST_ASSERT_CURRENT(1);
+    TEST_ASSERT_WATERMARK(1);
+
+    free(alloc2);
+
+    TEST_ASSERT_CURRENT(0);
+    TEST_ASSERT_WATERMARK(1);
+
+    malloc_monitor_reset_high_watermark();
+
+    TEST_ASSERT_CURRENT(0);
+    TEST_ASSERT_WATERMARK(0);
+}
+/*
+ * using calloc instead of malloc should be reflected correctly
+ */
+static void test_calloc(void)
+{
+    TEST_MALLOC_MONITOR_SAVE
+
+    TEST_ASSERT_CURRENT(0);
+    TEST_ASSERT_WATERMARK(0);
+
+    void *volatile alloc1 = calloc(1, MALLOC_SIZE);
+    TEST_ASSERT_NOT_NULL(alloc1);
+
+    TEST_ASSERT_CURRENT(1);
+    TEST_ASSERT_WATERMARK(1);
+
+    void *volatile alloc2 = calloc(2, MALLOC_SIZE);
+    TEST_ASSERT_NOT_NULL(alloc2);
+
+    TEST_ASSERT_CURRENT(3);
+    TEST_ASSERT_WATERMARK(3);
+
+    free(alloc1);
+
+    TEST_ASSERT_CURRENT(2);
+    TEST_ASSERT_WATERMARK(3);
+
+    malloc_monitor_reset_high_watermark();
+
+    TEST_ASSERT_CURRENT(2);
+    TEST_ASSERT_WATERMARK(2);
+
+    free(alloc2);
+
+    TEST_ASSERT_CURRENT(0);
+    TEST_ASSERT_WATERMARK(2);
+
+    malloc_monitor_reset_high_watermark();
+
+    TEST_ASSERT_CURRENT(0);
+    TEST_ASSERT_WATERMARK(0);
+}
+
+/*
+ * using realloc instead of malloc/free should be reflected correctly
+ */
+static void test_realloc(void)
+{
+    TEST_MALLOC_MONITOR_SAVE
+
+    TEST_ASSERT_CURRENT(0);
+    TEST_ASSERT_WATERMARK(0);
+
+    void *volatile alloc1 = realloc(NULL, MALLOC_SIZE);
+    TEST_ASSERT_NOT_NULL(alloc1);
+
+    TEST_ASSERT_CURRENT(1);
+    TEST_ASSERT_WATERMARK(1);
+
+    alloc1 = realloc(alloc1, 2*MALLOC_SIZE);
+    TEST_ASSERT_NOT_NULL(alloc1);
+
+    TEST_ASSERT_CURRENT(2);
+    TEST_ASSERT_WATERMARK(2);
+
+    alloc1 = realloc(alloc1, 1*MALLOC_SIZE);
+
+    TEST_ASSERT_CURRENT(1);
+    TEST_ASSERT_WATERMARK(2);
+
+    malloc_monitor_reset_high_watermark();
+
+    TEST_ASSERT_CURRENT(1);
+    TEST_ASSERT_WATERMARK(1);
+
+    alloc1 = realloc(alloc1, 0*MALLOC_SIZE);
+
+    TEST_ASSERT_CURRENT(0);
+    TEST_ASSERT_WATERMARK(1);
+
+    malloc_monitor_reset_high_watermark();
+
+    TEST_ASSERT_CURRENT(0);
+    TEST_ASSERT_WATERMARK(0);
+}
+
+/*
+ * freeing NULL shouldn't change anything
+ */
+static void test_free_NULL(void)
+{
+    TEST_MALLOC_MONITOR_SAVE
+
+    free(NULL);
+
+    TEST_ASSERT_CURRENT(0);
+    TEST_ASSERT_WATERMARK(0);
+
+    void *volatile alloc1 = malloc(MALLOC_SIZE);
+    TEST_ASSERT_NOT_NULL(alloc1);
+
+    TEST_ASSERT_CURRENT(1);
+    TEST_ASSERT_WATERMARK(1);
+
+    free(alloc1);
+
+    TEST_ASSERT_CURRENT(0);
+    TEST_ASSERT_WATERMARK(1);
+}
+
+static Test *tests_malloc_monitor(void)
+{
+    EMB_UNIT_TESTFIXTURES(fixtures) {
+        new_TestFixture(test_malloc_free),
+        new_TestFixture(test_calloc),
+        new_TestFixture(test_realloc),
+        new_TestFixture(test_free_NULL),
+    };
+
+    EMB_UNIT_TESTCALLER(tests, NULL, NULL, fixtures);
+    return (Test *)&tests;
+}
+
+int main(void)
+{
+    puts("malloc_monitor test");
+    TESTS_START();
+    TESTS_RUN(tests_malloc_monitor());
+    TESTS_END();
+
+    return 0;
+}

tests/sys/malloc_monitor/tests/01-run.py

@@ -0,0 +1,14 @@
+#!/usr/bin/env python3
+
+# Copyright (C) 2024 TU Dresden
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+
+import sys
+from testrunner import run_check_unittests
+
+
+if __name__ == "__main__":
+    sys.exit(run_check_unittests())