Sending an integer value instead of pointer using Queue

Mbed OS
1

In the class reference for Queue it says “The object type stored in the queue can be an integer, pointer or a generic type given by the template parameter T”.

However, in the docs it says only “A Queue allows you to queue pointers to data from producer threads to consumer threads.”, and this seems to be what is actually implemented.

I want to directly send integer values (send the actual value, not a pointer to it), but it seems like Queue doesn’t really support that except through misusing pointers by directly putting the integer value in a pointer. Here is what I mean by misusing pointers:

#include <mbed.h>

Thread get_thread(osPriorityNormal, OS_STACK_SIZE, nullptr, "get thread");
Thread put_thread(osPriorityNormal, OS_STACK_SIZE, nullptr, "put thread");

Queue<int, 32> q1;

void put_loop()
{
    int count = 0;
    while(true)
    {
        //All of the queue entries will point to this one integer pointer, but both threads are waiting 1 second between get/put
        //This is only for example purposes
        int* forced_value_into_pointer;
        // Store the value of count in the int pointer
        forced_value_into_pointer = (int*)count;

        bool put_status = q1.try_put(forced_value_into_pointer);

        count++;

        ThisThread::sleep_for(1s);
    }
}

void get_loop()
{
    //Class ref: "The message is stored in the location pointed to be the parameter data_out"
    int* queue_ptr;
    //Provide a pointer to a pointer so the queue knows where to store the pointer
    int** queue_ptr_ptr = &queue_ptr;

    while(true)
    {
        bool get_status = q1.try_get(queue_ptr_ptr);
        
        if(get_status)
        {
            printf("Get loop got: %d\n", queue_ptr);
            //OR:
            //printf("Get loop got: %d\n", *queue_ptr_ptr);
        }

        ThisThread::sleep_for(1s);
    }
}

int main()
{
    printf("Queue example\n");

    put_thread.start(put_loop);
    get_thread.start(get_loop);

    while(true)
    {
        ThisThread::sleep_for(1s);
    }
}

Is there a way to store an integer value in a Queue without pretending it’s a pointer to something?

2

I believe with passing integer it was meant to cast the integer into a pointer as you did, as pointers are the same size of an integer. Mbed uses the CMSIS RTOS API internally, which only accepts void pointers: Message Queue

So yes, you have to misuse pointers if you want to pass integers without allocating additional memory.

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