Disable the 100-continue feature

[WLBF]

Recently I meet the Session Object 100-continue problem. Once a request failed, the next time the cpr client will send Expect: 100-continue in next request with same url. Any idea about how to disable this feature.

Related:
https://curl.haxx.se/mail/lib-2017-07/0013.html

[fuzzbuster]

any solution?

[xloem]

Hey, I followed your link and looked up how to disable it, and it sounds like the way is simply to specify it as empty: https://gms.tf/when-curl-sends-100-continue.html#disabling-expect-logic . Have you tried this?

[COM8]

@xloem Would you like to create a PR for this?

[xloem]

I'm so sorry, I don't recall at all what I was working with that I visited this issue. I don't understand the issue at this time.

[leviliangtw]

Here I test this phenomenon with the following codes:

Url url{"http://www.example.com"};
std::string filename{"test_file"};
// prepare a file larger than 1 MB
std::string content{std::string(1024 * 1024, 'a')};
std::ofstream test_file;
test_file.open(filename);
test_file << content;
test_file.close();
Session session{};
curl_easy_setopt(session.GetCurlHolder()->handle, CURLOPT_VERBOSE, 1L);
session.SetUrl(url);
session.SetMultipart({{"file", File{"test_file"}}});
Response response = session.Post();

Then I got the following output:

*   Trying 93.184.216.34:80...
* Connected to www.example.com (93.184.216.34) port 80 (#0)
> POST / HTTP/1.1
Host: www.example.com
User-Agent: curl/7.80.0
Accept: */*
Accept-Encoding: deflate, gzip
Content-Length: 1048777
Content-Type: multipart/form-data; boundary=------------------------be95cef9532534a7
Expect: 100-continue

* We are completely uploaded and fine
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< Content-Encoding: gzip
< Accept-Ranges: bytes
< Cache-Control: max-age=604800
< Content-Type: text/html; charset=UTF-8
< Date: Tue, 26 Jul 2022 14:13:13 GMT
< Etag: "3147526947+gzip"
< Expires: Tue, 02 Aug 2022 14:13:13 GMT
< Last-Modified: Thu, 17 Oct 2019 07:18:26 GMT
< Server: EOS (vny/0453)
< Vary: Accept-Encoding
< Transfer-Encoding: chunked
< 
* Connection #0 to host www.example.com left intact

Therefore, I used the codes above to create a unit test and PR #798.