Re: [PATCH 1/6] libxl: libxl_device_disk_local_attach return a new libxl_device_disk

[Ian Jackson <Ian.Jackson@eu.citrix.com>]

Stefano Stabellini writes ("[PATCH 1/6] libxl: libxl_device_disk_local_attach return a new libxl_device_disk"):
> -char * libxl_device_disk_local_attach(libxl_ctx *ctx, libxl_device_disk *disk)
> +char * libxl_device_disk_local_attach(libxl_ctx *ctx, const libxl_device_disk *disk,
> +        libxl_device_disk **new_disk)

Long line.

Shouldn't we make this a libxl-internal function ?  If we do that we
can allocate the new libxl_device_disk from the gc.

> +    if (tmpdisk->pdev_path != NULL)
> +        tmpdisk->pdev_path = strdup(tmpdisk->pdev_path);
> +    if (tmpdisk->script != NULL)
> +        tmpdisk->script = strdup(tmpdisk->script);
> +    tmpdisk->vdev = NULL;

Perhaps you should put my "malloc always fails" patch on the bottom of
your series ?  That means you can write
   tmpdisk->pdev_path = libxl__strdup(0, tmpdisk->pdev_path);
which will crash more sanely if malloc fails.

> -    switch (disk->backend) {
> +    switch (tmpdisk->backend) {

If you renamed the formal parameter rather than introducing a new
variable this would all be a lot easier to read (both the patch, and
the resulting code).

>   out:
> -    if (dev != NULL)
> +    if (dev != NULL) {
>          ret = strdup(dev);
> +        tmpdisk->vdev = strdup(tmpdisk->vdev);
> +    }
>      GC_FREE;
>      return ret;

This leaks tmpdisk if the function fails.  Or, alternatively, you
expect the caller to always free *new_disk even if _attach fails,
which is very counterintuitive.

This would be solved if you made this an internal function and used
the gc.

Ian.