FreeRTOS Support Archive
The FreeRTOS support forum is used to obtain active support directly from Real
Time Engineers Ltd. In return for using our top quality software and services for
free, we request you play fair and do your bit to help others too! Sign up
to receive notifications of new support topics then help where you can.
This is a read only archive of threads posted to the FreeRTOS support forum.
The archive is updated every week, so will not always contain the very latest posts.
Use these archive pages to search previous posts. Use the Live FreeRTOS Forum
link to reply to a post, or start a new support thread.
[FreeRTOS Home] [Live FreeRTOS Forum] [FAQ] [Archive Top] [April 2010 Threads] Naked attribute in gccPosted by https://www.google.com/accounts on April 27, 2010 GCC documentation (http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html) states in 6.29 Declaring Attributes of Functions "naked Use this attribute on the ARM, AVR, IP2K, RX and SPU ports to indicate that the specified function does not need prologue/epilogue sequences generated by the compiler. It is up to the programmer to provide these sequences. The only statements that can be safely included in naked functions are asm statements that do not have operands. All other statements, including declarations of local variables, if statements, and so forth, should be avoided. Naked functions should be used to implement the body of an assembly function, while allowing the compiler to construct the requisite function declaration for the assembler." In the source of FreeRTOS for AVR I have seen the following: void vPortYield( void ) attribute ( ( naked ) ); void vPortYield( void ) { portSAVE_CONTEXT(); vTaskSwitchContext(); portRESTORE_CONTEXT(); asm volatile ( "ret" ); }
portSAVE_CONTEXT() and portRESTORE_CONTEXT() are macroses with asm but vTaskSwitchContext is a function My question is: Is the port for AVR of FreeRTOS is correct, or did I miss something?
RE: Naked attribute in gccPosted by Richard on April 27, 2010 I presume your point is "the naked function makes a C function call, but the GCC manual says you should only use asm statements". If so, then you are correct that in this case it goes against the advice, but it works fine, as far as I am aware, at all optimisation levels. In some ARM ports certain versions of GCC require the C function call to be replaced with a single asm statement that does exactly the same thing, but I have never known this to be the case with the AVR.
Are you having a problem with the generated code?
Regards.
RE: Naked attribute in gccPosted by https://www.google.com/accounts on April 27, 2010 Thank you for the answer.
No. I have not problem with the generated code.
My aim was to clarify my understanding of naked functions in GCC.
Copyright (C) Amazon Web Services, Inc. or its affiliates. All rights reserved.
|