Re: ipc/shm.c:494:18: warning: unused variable âhsâ [-Wunused-variable]

From: Borislav Petkov
Date: Wed May 08 2013 - 14:43:58 EST


On Wed, May 08, 2013 at 12:12:32PM -0400, Naoya Horiguchi wrote:
> Thank you for the report.
> I believe we can fix it with this one.
> ---
> From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> Date: Wed, 8 May 2013 11:48:01 -0400
> Subject: [PATCH] ipc/shm.c: don't use auto variable hs in newseg()
>
> This patch fixes "warning: unused variable 'hs'" when !CONFIG_HUGETLB_PAGE
> introduced by commit af73e4d9506d "hugetlbfs: fix mmap failure in unaligned
> size request".
>
> Reported-by: Borislav Petkov <bp@xxxxxxxxx>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> ---
> ipc/shm.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/ipc/shm.c b/ipc/shm.c
> index e316cb9..9ff741a 100644
> --- a/ipc/shm.c
> +++ b/ipc/shm.c
> @@ -491,9 +491,8 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
>
> sprintf (name, "SYSV%08x", key);
> if (shmflg & SHM_HUGETLB) {
> - struct hstate *hs = hstate_sizelog((shmflg >> SHM_HUGE_SHIFT)
> - & SHM_HUGE_MASK);
> - size_t hugesize = ALIGN(size, huge_page_size(hs));
> + size_t hugesize = ALIGN(size, huge_page_size(hstate_sizelog(
> + (shmflg >> SHM_HUGE_SHIFT) & SHM_HUGE_MASK)));

Yeah, it fixes the warning alright but makes the code more unreadable.
Which makes me wonder which is worse - to have an innocuous warning or
have unreadable code.

You could also do the below. The line sticks out but it kills the
warning. Readability is hmm, not optimal still though. :)

--
diff --git a/ipc/shm.c b/ipc/shm.c
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -491,9 +491,8 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)

sprintf (name, "SYSV%08x", key);
if (shmflg & SHM_HUGETLB) {
- struct hstate *hs = hstate_sizelog((shmflg >> SHM_HUGE_SHIFT)
- & SHM_HUGE_MASK);
- size_t hugesize = ALIGN(size, huge_page_size(hs));
+ unsigned long hsz = huge_page_size(hstate_sizelog((shmflg >> SHM_HUGE_SHIFT) & SHM_HUGE_MASK));
+ size_t hugesize = ALIGN(size, hsz);

/* hugetlb_file_setup applies strict accounting */
if (shmflg & SHM_NORESERVE)
--

Yeah, you decide.

Thanks.

--
Regards/Gruss,
Boris.

Sent from a fat crate under my desk. Formatting is fine.
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