Re: C++ pushback

["Alexander E. Patrakov" <patrakov@ums.usu.ru>]

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