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Re: [PATCH] http-backend: allow empty CONTENT_LENGTH




On Thu, Sep 06, 2018 at 11:38:31PM -0400, Jeff King wrote:
> My understanding from Jelmer's report is that a present-but-empty
> variable should be counted as "0" to mean "do not read any body bytes".
> That matches my reading of RFC 3875, which says:
> 
>   If no data is attached, then NULL (or unset).
> 
> (and earlier they explicitly define NULL as the empty string). That
> said, we do not do what they say for the "unset" case. And cannot
> without breaking chunked encoding from apache. So I don't know how much
> we want to follow that rfc to the letter, but at least it makes sense to
> me to revert this case back to what Git used to do, and what the rfc
> says.

I could find this discussion about it:
https://lists.gt.net/apache/users/373042

Basically, it says the CGI RFC was written before chunked
encoding appeared, so implementations should choose between
caching all boody before calling script, or breaking the
spec some way. So apache does it so.

(I wonder how IIS would handle it)

> In other words, I think the logic we want is:
> 
>   if (!str) {
> 	/*
> 	 * RFC3875 says this must mean "no body", but in practice we
> 	 * receive chunked encodings with no CONTENT_LENGTH. Tell the
> 	 * caller to read until EOF.
> 	 */
> 	val = -1;
>   } else if (!*str) {
> 	/*
> 	 * An empty length should be treated as "no body" according to
> 	 * RFC3875, and this seems to hold in practice.
> 	 */
> 	val = 0;
>   } else {
> 	/*
> 	 * We have a CONTENT_LENGTH; trust what's in it as long as it
> 	 * can be parsed.
> 	 */
> 	if (!git_parse_ssize_t(str, &val))
> 	        die(...);
>   }

I feel reluctant to treat empty and unset differently, but
probably this is the only thing which could be done.

I'll resumbmit some time later.