[Libguestfs] [PATCH] Fix lossy conversion of Content-Length

[Richard W.M. Jones]

On Wed, Jan 08, 2020 at 07:19:56AM -0600, Eric Blake wrote:
> On 1/7/20 4:13 AM, Adrian Ambrożewicz wrote:
> >Actual variable holding content length is int64_t, but it was assigned
> >by explicit cast to size_t. On 32-bit systems it's a lossy conversion,
> >so it was replaced by casting to int64_t instead.
> >
> >Signed-off-by: Adrian Ambrożewicz <adrian.ambrozewicz at linux.intel.com>
> >---
> >  plugins/curl/curl.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> >diff --git a/plugins/curl/curl.c b/plugins/curl/curl.c
> >index 031bd32..fe1330e 100644
> >--- a/plugins/curl/curl.c
> >+++ b/plugins/curl/curl.c
> >@@ -389,7 +389,7 @@ curl_open (int readonly)
> >      goto err;
> >    }
> >
> >-  h->exportsize = (size_t) d;
> >+  h->exportsize = (int64_t) d;
> 
> Why is a cast needed at all?
> This is C, an implicit conversion
> works just as well.

Present since the initial commit, but not present in the qemu
block/curl.c driver which is where most of this code was derived from,
so I suspect I simply added it "because reasons".

But even more to the point, why on earth does the
CURLINFO_CONTENT_LENGTH_DOWNLOAD API return a double!  Well it seems
as if they replaced that API with:

https://curl.haxx.se/libcurl/c/CURLINFO_CONTENT_LENGTH_DOWNLOAD_T.html

which is what we really ought to use instead.  This was added in Curl
7.55.0, released 2 and a half years ago, so I think we ought to use
that instead.  Adrian could you write a patch to change over to that
API?

Rich.

> >    nbdkit_debug ("content length: %" PRIi64, h->exportsize);
> >
> >    if (strncasecmp (url, "http://", strlen ("http://")) == 0 ||
> 
> -- 
> Eric Blake, Principal Software Engineer
> Red Hat, Inc.           +1-919-301-3226
> Virtualization:  qemu.org | libvirt.org
> 
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-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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