On Sat, 4 Jan 2014 22:29:31 +0900, Hitoshi Mitake wrote:
> Current nilfs_check_ondisk_sizes() checks sizes of important structs
> at run time. The checking should be done at build time. This patch
> adds a new macro, BUILD_BUG_ON(), for this purpose. It is similar to
> static_assert() of C++11. If an argument is true, the macro causes a
> bulid error.
>
> Below is an example of BUILD_BUG_ON(). When the checked conditions are
> true like below:
>
> /* intentional change for testing BUILD_BUG_ON() */
>
> static __attribute__((used)) void nilfs_check_ondisk_sizes(void)
> {
> BUILD_BUG_ON(sizeof(struct nilfs_inode) > NILFS_MIN_BLOCKSIZE);
> ...
>
> build process of mkfs.o causes errors like this:
>
> gcc -std=gnu99 -DHAVE_CONFIG_H -I. -I../.. -I../../include -Wall -g -O2 -MT
> mkfs.o -MD -MP -MF .deps/mkfs.Tpo -c -o mkfs.o mkfs.c
> mkfs.c: In function 'nilfs_check_ondisk_sizes':
> mkfs.c:429:2: error: negative width in bit-field '<anonymous>'
> mkfs.c:430:2: error: negative width in bit-field '<anonymous>'
> mkfs.c:431:2: error: negative width in bit-field '<anonymous>'
> mkfs.c:432:2: error: negative width in bit-field '<anonymous>'
> mkfs.c:433:2: error: negative width in bit-field '<anonymous>'
> mkfs.c:434:2: error: negative width in bit-field '<anonymous>'
> mkfs.c:435:2: error: negative width in bit-field '<anonymous>'
>
> Signed-off-by: Hitoshi Mitake <[email protected]>
This is an interesting patch.
I am inclined to apply this since the every test in the
nilfs_check_ondisk_sizes function is static.
If we will add a new check that depends on block size in a future, we
need to add a separate runtime check function as Vyacheslav wrote, but
I think you are doing right thing.
One my question is why you used bit operator. The BUILD_BUG_ON marcro
of kernel is implemented with negative array index.
Is there any reason for this ?
Thanks,
Ryusuke Konishi
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