Re: [PATCH] scsi: pm8001: avoid -Wrestrict warning

From: Jinpu Wang
Date: Wed Mar 24 2021 - 06:57:50 EST


On Tue, Mar 23, 2021 at 1:55 PM Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
>
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> On some configurations, gcc warns about overlapping source and
> destination arguments to snprintf:
>
> drivers/scsi/pm8001/pm8001_init.c: In function 'pm8001_request_msix':
> drivers/scsi/pm8001/pm8001_init.c:977:3: error: 'snprintf' argument 4 may overlap destination object 'pm8001_ha' [-Werror=restrict]
> 977 | snprintf(drvname, len, "%s-%d", pm8001_ha->name, i);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/scsi/pm8001/pm8001_init.c:962:56: note: destination object referenced by 'restrict'-qualified argument 1 was declared here
> 962 | static u32 pm8001_request_msix(struct pm8001_hba_info *pm8001_ha)
> | ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~
>
> I first assumed this was a gcc bug, as that should not happen, but
> a reduced test case makes it clear that this happens when the loop
> counter is not bounded by the array size.
>
> Help the compiler out by adding an explicit limit here to make the
> code slightly more robust and avoid the warning.
>
> Link: https://godbolt.org/z/6T1qPM
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Acked-by: Jack Wang <jinpu.wang@xxxxxxxxx>
> ---
> drivers/scsi/pm8001/pm8001_init.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/pm8001/pm8001_init.c b/drivers/scsi/pm8001/pm8001_init.c
> index bd626ef876da..a268c647b987 100644
> --- a/drivers/scsi/pm8001/pm8001_init.c
> +++ b/drivers/scsi/pm8001/pm8001_init.c
> @@ -963,6 +963,7 @@ static u32 pm8001_request_msix(struct pm8001_hba_info *pm8001_ha)
> {
> u32 i = 0, j = 0;
> int flag = 0, rc = 0;
> + int nr_irqs = pm8001_ha->number_of_intr;
>
> if (pm8001_ha->chip_id != chip_8001)
> flag &= ~IRQF_SHARED;
> @@ -971,7 +972,10 @@ static u32 pm8001_request_msix(struct pm8001_hba_info *pm8001_ha)
> "pci_enable_msix request number of intr %d\n",
> pm8001_ha->number_of_intr);
>
> - for (i = 0; i < pm8001_ha->number_of_intr; i++) {
> + if (nr_irqs > ARRAY_SIZE(pm8001_ha->intr_drvname))
> + nr_irqs = ARRAY_SIZE(pm8001_ha->intr_drvname);
> +
> + for (i = 0; i < nr_irqs; i++) {
> snprintf(pm8001_ha->intr_drvname[i],
> sizeof(pm8001_ha->intr_drvname[0]),
> "%s-%d", pm8001_ha->name, i);
> --
> 2.29.2
>