Quality RTOS & Embedded Software

 Real time embedded FreeRTOS RSS feed 
Quick Start Supported MCUs PDF Books Trace Tools Ecosystem TCP & FAT




Loading

GCC ARM port and use of -fomit-frame-pointer

Posted by *anonymous on April 14, 2007

I see the GCC ARM port issue regarding thread unsafe function returns is still biting people. I find the use of -fomit-frame-pointer interferes with some debuggers' abilities to unwind the stack. Some time ago I suggested a FreeRTOS port fix for it. I have been using the fix successfully for some time now. It seems to take care of the issue. I think it should be in the official ARM port so that the problem doesn't keep coming back.

Here it is again (without explanation): In the portSAVE_CONTEXT() macro of portmacro.h add the commented line in the position shown below

____/* Set R0 to point to the task stack pointer. */  ________"STMDB    SP,{SP}^            nt" ________"NOP                        nt" ________"SUB    SP, SP, #4          nt" ________"LDMIA    SP!,{R0}            nt"                                           /*gb - step over possible GCC stacked items (GCC bug)*/ ________"SUB    R0, R0, #8          nt"


GCC ARM port and use of -fomit-frame-pointer

Posted by nobody on April 19, 2007

No response to this?  Looks like a good idea.

Does this mean it uses an extra 8 bytes of RAM for each context?  Should not be a problem I don't think.


GCC ARM port and use of -fomit-frame-pointer

Posted by *anonymous on April 19, 2007

Yes, eight bytes of stack space are wasted for each task, except the running task (and except for those tasks that were in the non thread-safe state when their context was saved). Also, the cost of a context switch goes up by the execution of one register-to-register instruction.


[ Back to the top ]    [ About FreeRTOS ]    [ Sitemap ]    [ ]




Copyright (C) Amazon Web Services, Inc. or its affiliates. All rights reserved.

Latest News

FreeRTOS kernel V10 is available for immediate download. Now MIT licensed.


FreeRTOS Partners

ARM Connected RTOS partner for all ARM microcontroller cores

IAR Partner

Microchip Premier RTOS Partner

RTOS partner of NXP for all NXP ARM microcontrollers

STMicro RTOS partner supporting ARM7, ARM Cortex-M3, ARM Cortex-M4 and ARM Cortex-M0

Texas Instruments MCU Developer Network RTOS partner for ARM and MSP430 microcontrollers

OpenRTOS and SafeRTOS