2022-06-07 20:30:57

by Jiri Slaby

Subject: Re: [PATCH 12/36] tty/vt: consolemap: use sizeof(*pointer) instead of sizeof(type)

On 07. 06. 22, 16:00, Ilpo Järvinen wrote:
> On Tue, 7 Jun 2022, Jiri Slaby wrote:
>
>> It is preferred to use sizeof(*pointer) instead of sizeof(type). First,
>> the type of the variable can change and one needs not change the former
>> (unlike the latter). Second, the latter is error-prone due to (u16),
>> (u16 *), and (u16 **) mixture here.
>>
>> Signed-off-by: Jiri Slaby <[email protected]>
>
> Reviewed-by: Ilpo Järvinen <[email protected]>
>
> This seems fine but see the comments below which are not directly related
> to the change itself.
>
>> ---
>> drivers/tty/vt/consolemap.c | 23 ++++++++++++-----------
>> 1 file changed, 12 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
>> index 097ab7d01f8b..79a62dcca046 100644
>> --- a/drivers/tty/vt/consolemap.c
>> +++ b/drivers/tty/vt/consolemap.c
>> @@ -251,12 +251,12 @@ static void set_inverse_trans_unicode(struct vc_data *conp,
>> return;
>> q = p->inverse_trans_unicode;
>> if (!q) {
>> - q = p->inverse_trans_unicode =
>> - kmalloc_array(MAX_GLYPH, sizeof(u16), GFP_KERNEL);
>> + q = p->inverse_trans_unicode = kmalloc_array(MAX_GLYPH,
>> + sizeof(*q), GFP_KERNEL);
>> if (!q)
>> return;
>> }
>> - memset(q, 0, MAX_GLYPH * sizeof(u16));
>> + memset(q, 0, MAX_GLYPH * sizeof(*q));
>
> Convert kmalloc_array into kcalloc and place memset() into else branch?

IMO, the way it is now is more obvious.

>> @@ -514,11 +514,12 @@ con_insert_unipair(struct uni_pagedict *p, u_short unicode, u_short fontpos)
>> n = UNI_ROW(unicode);
>> p2 = p1[n];
>> if (!p2) {
>> - p2 = p1[n] = kmalloc_array(UNI_ROW_GLYPHS, sizeof(u16), GFP_KERNEL);
>> + p2 = p1[n] = kmalloc_array(UNI_ROW_GLYPHS, sizeof(*p2),
>> + GFP_KERNEL);
>> if (!p2)
>> return -ENOMEM;
>> /* No glyphs for the characters (yet) */
>> - memset(p2, 0xff, UNI_ROW_GLYPHS * sizeof(u16));
>> + memset(p2, 0xff, UNI_ROW_GLYPHS * sizeof(*p2));
>
> This could have been kcalloc'ed.

Why would you zero it before setting it to 0xff?

thanks,
--
js
suse labs

2022-06-08 08:42:09

by Ilpo Järvinen

Subject: Re: [PATCH 12/36] tty/vt: consolemap: use sizeof(*pointer) instead of sizeof(type)

On Tue, 7 Jun 2022, Jiri Slaby wrote:

> On 07. 06. 22, 16:00, Ilpo Järvinen wrote:
> > On Tue, 7 Jun 2022, Jiri Slaby wrote:
> >
> > > It is preferred to use sizeof(*pointer) instead of sizeof(type). First,
> > > the type of the variable can change and one needs not change the former
> > > (unlike the latter). Second, the latter is error-prone due to (u16),
> > > (u16 *), and (u16 **) mixture here.
> > >
> > > Signed-off-by: Jiri Slaby <[email protected]>
> >
> > Reviewed-by: Ilpo Järvinen <[email protected]>
> >
> > This seems fine but see the comments below which are not directly related
> > to the change itself.
> >
> > > ---
> > > drivers/tty/vt/consolemap.c | 23 ++++++++++++-----------
> > > 1 file changed, 12 insertions(+), 11 deletions(-)
> > >
> > > diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
> > > index 097ab7d01f8b..79a62dcca046 100644
> > > --- a/drivers/tty/vt/consolemap.c
> > > +++ b/drivers/tty/vt/consolemap.c
> > > @@ -251,12 +251,12 @@ static void set_inverse_trans_unicode(struct vc_data
> > > *conp,
> > > return;
> > > q = p->inverse_trans_unicode;
> > > if (!q) {
> > > - q = p->inverse_trans_unicode =
> > > - kmalloc_array(MAX_GLYPH, sizeof(u16), GFP_KERNEL);
> > > + q = p->inverse_trans_unicode = kmalloc_array(MAX_GLYPH,
> > > + sizeof(*q), GFP_KERNEL);
> > > if (!q)
> > > return;
> > > }
> > > - memset(q, 0, MAX_GLYPH * sizeof(u16));
> > > + memset(q, 0, MAX_GLYPH * sizeof(*q));
> >
> > Convert kmalloc_array into kcalloc and place memset() into else branch?
>
> IMO, the way it is now is more obvious.

Fair enough.

> > > @@ -514,11 +514,12 @@ con_insert_unipair(struct uni_pagedict *p, u_short
> > > unicode, u_short fontpos)
> > > n = UNI_ROW(unicode);
> > > p2 = p1[n];
> > > if (!p2) {
> > > - p2 = p1[n] = kmalloc_array(UNI_ROW_GLYPHS, sizeof(u16),
> > > GFP_KERNEL);
> > > + p2 = p1[n] = kmalloc_array(UNI_ROW_GLYPHS, sizeof(*p2),
> > > + GFP_KERNEL);
> > > if (!p2)
> > > return -ENOMEM;
> > > /* No glyphs for the characters (yet) */
> > > - memset(p2, 0xff, UNI_ROW_GLYPHS * sizeof(u16));
> > > + memset(p2, 0xff, UNI_ROW_GLYPHS * sizeof(*p2));
> >
> > This could have been kcalloc'ed.
>
> Why would you zero it before setting it to 0xff?

Yes, nevermind that. I obviously completely missed the fact it wasn't
memsetting to zero.

--
i.