Inline Macro issue

[Valdis.Kletnieks at vt.edu]

On Mon, 15 Jul 2013 17:39:15 +0530, Mandeep Sandhu said:

> #define push_root() \
> 	recursive_mutex_lock(&context->id_lock);	\
> 	context->uid = current->fsuid;			\
> 	context->gid = current->fsgid;			\
>         do {                                            \
>             struct cred *new1 = prepare_creds();           \
>             //make changes to any member of this structure \
>             commit_creds(new1);                            \
>         } while(0);

Actually, this has 3 problems:

1) You have a call to mutex_loc() that doesn't get unlocked. This Is Bad.

2) If you're using the 'do { foo } while (0)' trick, you want to
put the *whole thing* inside the { } (Hint - you can put local variable
definitions inside the curlies as well).

3) Leave the ; off the 'while (0)' in the macro definition, because:

> int main()
> {
>    printf("in main\n");
>    pushme
>   return 0;
> }

Somebody will forget and put a ; after pushme - and in some contexts, the
additional ; will then cause issues.

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