Inline Macro issue

[Srinivas Ganji]

A small suggestion, use begin { and end } braces for declaring your macro.
May be I am wrong, but you can try this. Then, the declaration become local
to that block.

Regards,
Srinivas


On Mon, Jul 15, 2013 at 1:03 AM, Saket Sinha <saket.sinha89 at gmail.com>wrote:

> "current" in kernel is a global macro, that always point to the "struct
> task_struct * " of the currently executing task (for details on
> task_struct, ref Robert Love, pg 24-27).
>
>  Now I have a macro called push root which has the following purpose-
> "to push  root user and group to current context so to set current uid and
> gid to 0."
>
>  Now in kernel 3.8.3, I would do something like
>
> struct cred *new1;
> new1 =prepare_creds();
> new1->uid = 0;
> new1->gid = 0;
> commit_creds(new1);
>
> So macro definition of push root, according to what I have proposed above,
> should be
> #define push_root               \
> new1 =prepare_creds();      \
> new1->uid = 0;                   \
> new1->gid = 0;                   \
> commit_creds(new1)
>
> But I am getting errors like multiple declaration of new1 etc.
>
> Even if I declare prepare_creds outside macro definition like
>
> new1 =prepare_creds();
> #define push_root               \
> new1->uid = 0;                   \
> new1->gid = 0;                   \
> commit_creds(new1)
>
> I think I am  facing the issue that the macros are inlined during
> compilation, so when the compiler wants to replace them, it raises issues.
>
> I could think of two ways to solve this issue-
>
> 1. define a new macro like #define prep_root() which defines the var once
> for all, and that I have to put it at the begin of each function needing
> push_root. This is not a very good method.
>
> 2. I should still try to go with inlined functions but how ?
>
> Can someone suggest anything
>
> Regards,
> Saket Sinha
>
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