Hello Team, We are trying to include Renesas RX65N architecture in GitHub pre-check which requires code to have 0 warnings to be successful.
Call to up_copystate() in the below functions produces warnings in NuttX common files: arch/renesas/src/common/up_blocktask.c: up_block_task() arch/renesas/src/common/up_releasepending: up_release_pending() arch/renesas/src/common/up_reprioritizertr: up_reprioritize_rtr() arch/renesas/src/common/up_unblocktask: up_unblock_task() Changes in the above files will affect the other Renesas architectures (m16c and sh1) as well. The function prototype of up_copystate() in file: "arch/renesas/src/common/up_internal.h" is as follows: void up_copystate(uint32_t *dest, uint32_t *src); g_current_regs is also defined in the same file as: extern volatile uint32_t *g_current_regs; Calling up_copystate() with g_current_regs as 2nd argument gives the following warning: passing argument 2 of ‘up_copystate’ discards ‘volatile’ qualifier from pointer target type [-Werror] up_copystate(rtcb->xcp.regs, g_current_regs); ^ The above call causes the 'volatile' nature of g_current_regs to be lost. We understand that casting away the 'volatile' type qualifier of a variable should be avoided if possible. We intend to do a PR by modifying the prototype of the above function to: void up_copystate(uint32_t *dest, volatile uint32_t *src); This modification produces the same warning in memcpy() function call. Typecasting the argument when calling memcpy() alone will resolve this warning. This retains the volatile nature of the variable as well as resolves the warnings produced due to the above function call with volatile g_current_regs argument. Are there any concerns with the above mentioned modifications? Regards, Bhindhiya Raja. ________________________________ From: Bhindhiya Raja <bhindhiy...@tataelxsi.co.in> Sent: Monday, September 14, 2020 5:09 PM To: dev@nuttx.apache.org <dev@nuttx.apache.org> Subject: Re: Warnings in Renesas common files 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. 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