Re: [PATCH [repost]] block/blkio: Don't assume size_t is 64 bit

[Kevin Wolf <kwolf@redhat.com>]

Am 29.01.2024 um 19:53 hat Richard W.M. Jones geschrieben:
> With GCC 14 the code failed to compile on i686 (and was wrong for any
> version of GCC):
> 
> ../block/blkio.c: In function ‘blkio_file_open’:
> ../block/blkio.c:857:28: error: passing argument 3 of ‘blkio_get_uint64’ from incompatible pointer type [-Wincompatible-pointer-types]
>   857 |                            &s->mem_region_alignment);
>       |                            ^~~~~~~~~~~~~~~~~~~~~~~~
>       |                            |
>       |                            size_t * {aka unsigned int *}
> In file included from ../block/blkio.c:12:
> /usr/include/blkio.h:49:67: note: expected ‘uint64_t *’ {aka ‘long long unsigned int *’} but argument is of type ‘size_t *’ {aka ‘unsigned int *’}
>    49 | int blkio_get_uint64(struct blkio *b, const char *name, uint64_t *value);
>       |                                                         ~~~~~~~~~~^~~~~
> 
> Signed-off-by: Richard W.M. Jones <rjones@redhat.com>

Why not simply make BDRVBlkioState.mem_region_alignment a uint64_t
instead of keeping it size_t and doing an additional conversion with
a check that requires an #if (probably to avoid a warning on 64 bit
hosts because the condition is never true)?

Kevin

>  block/blkio.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/block/blkio.c b/block/blkio.c
> index 0a0a6c0f5fd..52d78935147 100644
> --- a/block/blkio.c
> +++ b/block/blkio.c
> @@ -794,6 +794,7 @@ static int blkio_file_open(BlockDriverState *bs, QDict *options, int flags,
>      const char *blkio_driver = bs->drv->protocol_name;
>      BDRVBlkioState *s = bs->opaque;
>      int ret;
> +    uint64_t val;
>  
>      ret = blkio_create(blkio_driver, &s->blkio);
>      if (ret < 0) {
> @@ -854,7 +855,7 @@ static int blkio_file_open(BlockDriverState *bs, QDict *options, int flags,
>  
>      ret = blkio_get_uint64(s->blkio,
>                             "mem-region-alignment",
> -                           &s->mem_region_alignment);
> +                           &val);
>      if (ret < 0) {
>          error_setg_errno(errp, -ret,
>                           "failed to get mem-region-alignment: %s",
> @@ -862,6 +863,15 @@ static int blkio_file_open(BlockDriverState *bs, QDict *options, int flags,
>          blkio_destroy(&s->blkio);
>          return ret;
>      }
> +#if HOST_LONG_BITS == 32
> +    if (val > SIZE_MAX) {
> +        error_setg_errno(errp, ERANGE,
> +                         "mem-region-alignment too large for size_t");
> +        blkio_destroy(&s->blkio);
> +        return -ERANGE;
> +    }
> +#endif
> +    s->mem_region_alignment = (size_t)val;
>  
>      ret = blkio_get_bool(s->blkio,
>                           "may-pin-mem-regions",
> -- 
> 2.43.0
>