[1] The local warning suppression added to the macro does not work as the
warning suppression is effected only after the complier encounter the first
curly brace "{" (which does not appear in this specific MACRO)
#define OBJECT_OFFSETOF(OBJECT, MEMBER) __pragma(warning(push)
__pragma(warning(disable:4700)) ((char *)&(OBJECT)->MEMBER - (char *)(OBJECT))
__pragma(warning(push)
[2] The usage of the decltype does work with of a built in VS project I
created:
#define OBJECT_OFFSETOF(OBJECT, MEMBER) \
((LONG)(LONG_PTR)&((decltype(OBJECT))0)->MEMBER)
I think it is the right way to implement it. But, this keyword "decltype" is
ignored by the compiler when above macro is used in the OVS source base. I
don't know the reason for it but it might be related to custom compilation
options we use (or others we don't use).
-----Original Message-----
From: Ben Pfaff [mailto:b...@nicira.com]
Sent: Thursday, September 11, 2014 12:27 PM
To: Eitan Eliahu
Cc: Gurucharan Shetty; dev@openvswitch.org; Gurucharan Shetty
Subject: Re: [ovs-dev] [PATCH 3/3] Avoid uninitialized variable warnings with
OBJECT_OFFSETOF() in MSVC.
On Thu, Sep 11, 2014 at 07:20:13PM +0000, Eitan Eliahu wrote:
>
> Here is the local warning suppression :
> #define OBJECT_OFFSETOF(OBJECT, MEMBER) __pragma(pack(push, 1))
> __pragma(warning(disable:4700)) ((char *)&(OBJECT)->MEMBER - (char
> *)(OBJECT)) __pragma(pack(pop))
>
>
> The right way to do it is as follows, but it doesn't work on OVS source base,
>
> struct my_node {
> int first;
> int extra_data;
> };
>
> #define OBJECT_OFFSETOF1(OBJECT, MEMBER) \
> ((LONG)(LONG_PTR)&((decltype(OBJECT))0)->MEMBER)
>
> int _tmain(int argc, _TCHAR* argv[])
> {
> long l1 = (long)OBJECT_OFFSETOF1(node, extra_data);
> printf("Number is %d\n", l1);
> return 0;
> }
Do you know why it doesn't work?
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