Re: C++ pushback

Alexander E. Patrakov
2006-04-27T09:07:44Z

J.A. Magallon wrote:
> Tell me what is the difference between:
>
>
> sbi = kmalloc(sizeof(*sbi), GFP_KERNEL);
> if (!sbi)
> return -ENOMEM;
> sb->s_fs_info = sbi;
> memset(sbi, 0, sizeof(*sbi));
> sbi->s_mount_opt = 0;
> sbi->s_resuid = EXT3_DEF_RESUID;
> sbi->s_resgid = EXT3_DEF_RESGID;
>
> and
>
> SuperBlock() : s_mount_opt(0), s_resuid(EXT3_DEF_RESUID), s_resgid(EXT3_DEF_RESGID)
> {}
>
> ...
> sbi = new SuperBlock;
> if (!sbi)
> return -ENOMEM;
>
> apart that you don't get members initalized twice and get a shorter code :).

The second example is simply incorrect, because the operator new throws an
exception when we run out of memory, instead of returning a null pointer.

So it has to be written as:

sbi = new SuperBlock;
/* The rest of code assumes that the sbi pointer is valid. If this was not the
case, let's hope that the caller caught std::bad_alloc properly */

--
Alexander E. Patrakov