[v2,07/12] xen/include: import sizeof_field() macro from Linux stddef.h

Commit Message

Paul Durrant Nov. 20, 2020, 9:48 a.m. UTC

From: Paul Durrant <[e-mail]>

Co-locate it with the definition of offsetof() (since this is also in stddef.h
in the Linux kernel source). This macro will be needed in a subsequent patch.

Signed-off-by: Paul Durrant <[e-mail]>
---
Cc: Andrew Cooper <[e-mail]>
Cc: George Dunlap <[e-mail]>
Cc: Ian Jackson <[e-mail]>
Cc: Jan Beulich <[e-mail]>
Cc: Julien Grall <[e-mail]>
Cc: Stefano Stabellini <[e-mail]>
Cc: Wei Liu <[e-mail]>
---
 xen/include/xen/compiler.h | 8 ++++++++
 1 file changed, 8 insertions(+)

Comments

Jan Beulich Nov. 20, 2020, 3:15 p.m. UTC | #1

On 20.11.2020 10:48, Paul Durrant wrote:
> From: Paul Durrant <[e-mail]>
> 
> Co-locate it with the definition of offsetof() (since this is also in stddef.h
> in the Linux kernel source). This macro will be needed in a subsequent patch.
> 
> Signed-off-by: Paul Durrant <[e-mail]>

Acked-by: Jan Beulich <[e-mail]>

You don't fancy replacing in the tree what is now effectively
open-coding this construct, I guess? I'll try to remember to
do so once this has gone in...

Jan

Paul Durrant Nov. 20, 2020, 3:24 p.m. UTC | #2

> -----Original Message-----
> From: Jan Beulich <[e-mail]>
> Sent: 20 November 2020 15:16
> To: Paul Durrant <[e-mail]>
> Cc: Paul Durrant <[e-mail]>; Andrew Cooper <[e-mail]>; George Dunlap
> <[e-mail]>; Ian Jackson <[e-mail]>; Julien Grall <[e-mail]>; Stefano
> Stabellini <[e-mail]>; Wei Liu <[e-mail]>; [e-mail]
> Subject: Re: [PATCH v2 07/12] xen/include: import sizeof_field() macro from Linux stddef.h
> 
> On 20.11.2020 10:48, Paul Durrant wrote:
> > From: Paul Durrant <[e-mail]>
> >
> > Co-locate it with the definition of offsetof() (since this is also in stddef.h
> > in the Linux kernel source). This macro will be needed in a subsequent patch.
> >
> > Signed-off-by: Paul Durrant <[e-mail]>
> 
> Acked-by: Jan Beulich <[e-mail]>
> 
> You don't fancy replacing in the tree what is now effectively
> open-coding this construct, I guess? I'll try to remember to
> do so once this has gone in...
> 

I'll see what I can find after this series is in, unless you get there first :-)

  Paul

Patch

diff --git a/xen/include/xen/compiler.h b/xen/include/xen/compiler.h
index c0e0ee9f27be..676c6ea1b0a0 100644
--- a/xen/include/xen/compiler.h
+++ b/xen/include/xen/compiler.h
@@ -76,6 +76,14 @@ 
 
 #define offsetof(a,b) __builtin_offsetof(a,b)
 
+/**
+ * sizeof_field(TYPE, MEMBER)
+ *
+ * @TYPE: The structure containing the field of interest
+ * @MEMBER: The field to return the size of
+ */
+#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
+
 #if !defined(__STDC_VERSION__) || __STDC_VERSION__ < 201112L
 #define alignof __alignof__
 #endif