Hello Greg and Nathan, Any input on the warnings generated due to the g_current_regs volatile type qualifier?
Best Regards, Bhindhiya Raja SBU | Engineer TATA ELXSI LIMITED ITPB Road Whitefield Bengaluru 560 048 India www.tataelxsi.com<https://apc01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.tataelxsi.com%2F&data=02%7C01%7Cbhindhiya.r%40tataelxsi.co.in%7C27f3ef9461c64949d6e508d832f8ecbc%7Cad6a39dd96b6436882daf2ec4d92e26a%7C0%7C0%7C637315393618704041&sdata=FdDPWsO9WgR7HscuY%2BLQkX1oTtr%2BuNpCgEl35LtrZZ8%3D&reserved=0> ________________________________ From: Nathan Hartman <hartman.nat...@gmail.com> Sent: Saturday, September 5, 2020 3:51 AM To: dev@nuttx.apache.org <dev@nuttx.apache.org> Subject: Re: Warnings in Renesas common files ________________________________ **This is an external email. Please check the sender’s full email address (not just the sender name) and exercise caution before you respond or click any embedded link/attachment.** ________________________________ On Fri, Sep 4, 2020 at 9:40 AM Bhindhiya Raja <bhindhiy...@tataelxsi.co.in.invalid> wrote: > > Hello Nathan, > > Thank you for your response. We have submitted 2 separate PRs as recommended > by you to resolve warnings 6 (#1695) and 8 (#1702). > > About warnings 1 to 4, we understand that casting away the 'volatile' type > qualifier of a variable should be avoided if possible. Can we consider > modifying the prototype of the function up_copystate() in up_internal.h file, > from: > void up_copystate(uint32_t *dest, uint32_t *src); > to: > void up_copystate(uint32_t *dest, volatile uint32_t *src); > in order to resolve this warning. > > We have tried the above fix in our local repository and checked build. > We found that warnings 1 to 4 are resolved, however, it generates a new > warning in file: > arch/renesas/src/rx65n/rx65n_copystate.c: passing argument 2 of > ‘up_copystate’ discards ‘volatile’ qualifier from pointer target type > memcpy(dest, src, XCPTCONTEXT_SIZE); > > expected ‘const void *’ but argument is of type ‘volatile uint32_t *’ > FAR void *memcpy(FAR void *dest, FAR const void *src, size_t n); > > This can be resolved by typecasting the variables when calling memcpy() alone. > > As these files are common to other Renesas architectures as well, please > confirm if the above modifications are okay. Hello Bhindhiya, I am not sure what is the best choice here. I looked through NuttX sources and I did not see any up_copystate() (for any arch) that had volatile qualifiers. That said, looking at the call to up_copystate() in up_unblock_task(), g_current_regs is indeed volatile (for good reasons), so I wonder if we should propagate that as far as possible, until the memcpy(), like you're suggesting, or, alternatively, if it is safe to discard volatile like is being done already, because we are switching tasks. I need to think about this some more. Maybe Greg will share some of his wisdom with us. :-) Nathan ________________________________ Disclaimer: This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you are not the intended recipient of this message , or if this message has been addressed to you in error, please immediately alert the sender by reply email and then delete this message and any attachments. If you are not the intended recipient, you are hereby notified that any use, dissemination, copying, or storage of this message or its attachments is strictly prohibited. Email transmission cannot be guaranteed to be secure or error-free, as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or contain viruses. The sender, therefore, does not accept liability for any errors, omissions or contaminations in the contents of this message which might have occurred as a result of email transmission. If verification is required, please request for a hard-copy version. ________________________________
