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Mbed OS provides a set of debug functions that you can use to output debug messages to STDIO at runtime. mbed_debug.h declares these functions, which are available only in debug builds.

The debug function is a printf-style function that takes a format string followed by arguments. Below are some sample usages.

void *operator new(std::size_t count) {
    void *buffer = malloc(count);
    if (NULL == buffer) {
        error("Operator new out of memory\r\n");
    } else {
        debug("Operator new succeded");
    return buffer;

The debug_if function is similar to the debug function except that it takes an additional argument as its first parameter. The message prints to STDIO only if the first paramater evaluates to true.

void *operator new(std::size_t count) {
    debug_if( count == 0, "\nnew called with 0 size");

Debug functions reference

Debug example

 * Copyright (c) 2017 - 2020 Arm Limited and affiliates.
 * SPDX-License-Identifier: Apache-2.0

#include "mbed.h"

#define MAX_THREAD_INFO 10

mbed_stats_heap_t heap_info;
mbed_stats_stack_t stack_info[ MAX_THREAD_INFO ];
int main()
    debug("\nThis message is from debug function");
    debug_if(1, "\nThis message is from debug_if function");
    debug_if(0, "\nSOMETHING WRONG!!! This message from debug_if function shouldn't show on bash");

    printf("\n\tBytes allocated currently: %ld", heap_info.current_size);
    printf("\n\tMax bytes allocated at a given time: %ld", heap_info.max_size);
    printf("\n\tCumulative sum of bytes ever allocated: %ld", heap_info.total_size);
    printf("\n\tCurrent number of bytes allocated for the heap: %ld", heap_info.reserved_size);
    printf("\n\tCurrent number of allocations: %ld", heap_info.alloc_cnt);
    printf("\n\tNumber of failed allocations: %ld", heap_info.alloc_fail_cnt);

    printf("\nCumulative Stack Info:");
    printf("\n\tMaximum number of bytes used on the stack: %ld", stack_info[0].max_size);
    printf("\n\tCurrent number of bytes allocated for the stack: %ld", stack_info[0].reserved_size);
    printf("\n\tNumber of stacks stats accumulated in the structure: %ld", stack_info[0].stack_cnt);

    mbed_stats_stack_get_each(stack_info, MAX_THREAD_INFO);
    printf("\nThread Stack Info:");
    for (int i = 0; i < MAX_THREAD_INFO; i++) {
        if (stack_info[i].thread_id != 0) {
            printf("\n\tThread: %d", i);
            printf("\n\t\tThread Id: 0x%08lX", stack_info[i].thread_id);
            printf("\n\t\tMaximum number of bytes used on the stack: %ld", stack_info[i].max_size);
            printf("\n\t\tCurrent number of bytes allocated for the stack: %ld", stack_info[i].reserved_size);
            printf("\n\t\tNumber of stacks stats accumulated in the structure: %ld", stack_info[i].stack_cnt);


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