Hello, I’m just new to FreeRTOS. I was able to get it up and running on my environment (details below) by creating two simple tasks which output something to the UART. Depending on the UART speed settings etc I can force overlapping outputs which is good to learn how to synchronize/serialize the ou…

Personally, I made a copy of heap_3 that I called heap_malloc that removes the calls to the schedule suspend/resume around the calls to malloc and free, and include the function __malloc_lock() and __malloc_unlock() to make malloc and family thread safe. That way the FreeRTOS heap function calls st…

Hello Hartmut & Richard, thank you for your answers. @hs2 : I’m not sure if I understood it correctly - you mean I can stay with heap_4 and define pvPortMalloc and pvPortFree as the newlib malloc()/free() ? Regarding the newer version of the toolchain, I’ve setup a small non-RTOS project with the…

[image] RA1981: stay with heap_4 and define pvPortMalloc and pvPortFree as the newlib malloc()/free() Sorry - no. I thought you were talking about using heap_3 which is using newlib malloc/free internally. The missing syscalls should by implemented maybe as empty functions/stubs if you don’t…

Sorry - no. I thought you were talking about using heap_3 which is using newlib malloc/free internally. Ah, okay. As I mentioned, the first idea was to take heap_4, but then I realized that it might fail with printf(). The application in its current state does well with the newlib heap implementa…

UPDATE: it seems that the new newlib version indeed uses the lock/unlock mechanism and I was able to override it, currently using void __malloc_lock(struct _reent *r) { vTaskSuspendAll(); } void __malloc_unlock(__attribute__((unused)) struct _reent *r) { xTaskResumeAll(); } I verified that thos…

the __malloc_lock and __malloc_unlock will NOT keep multiple tasks output from interleaving. That will require something that handles “message” level concepts. If you want that to be at the “printf” level, then you will likely need to wrap printf, so that you can acquire and release a mutex around e…

Hello @richard-damon first a question about using vTaskSuspendAll()/XtaskResumeAll() for the locking mechanism: is this the right way to do it? Regarding wrapping printf(), why do I also need to wrap vprintf()? Or do you mean that instead of having a function which wraps printf() with a mutex I ca…

You commented that you didn’t want multiple tasks output to interleave. Without something to block this, it could happen. Thus, if the goal is that every call to printf be made “atomic” as far as output, then you need to make sure that only one task at a time is inside printf. as for wrapping mallo…

Oh, okay… well, then it seems there’s no other way than to stay with heap_3. And I’ll use a mutex for printf()/vprintf() if needed. But first I’ll check the current application implementation about what can be splitted into separate tasks. Thank you.

As Richard mentioned there are a few more functions to wrap to completely replace the newlib heap with e.g. FreeRTOS heap_4. You need to override/wrap these heap API functions: malloc_r , free_r , calloc_r and realloc_r. But ask yourself if it’s worth the effort if you’re fine with the newlib heap…

Question about using printf() / malloc() with heap_4 & newlib

Kernel

jefftenney (Jeff) January 31, 2024, 12:33am 14

If you’re sticking with heap_3 with newlib for now, then see this post for some helpful code (if I do say so myself ).

Topic		Replies	Views
Printf using printf-stdarg.c (2022) Kernel	3	4003	July 15, 2022
How to make printf/sprintf/strtod thread safe Kernel	15	2620	June 5, 2018
Thread safe memory allocation Kernel	25	15165	March 17, 2021
using newlib with FreeRTOS - comments please? Kernel	22	1988	January 20, 2021
printf and heap_4 Kernel	9	1088	February 14, 2020

Question about using printf() / malloc() with heap_4 & newlib

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