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Jay Satiro 798a37b25e lib: clear the easy handle's saved errno before transfer

- Clear data->state.os_errno before transfer.

- Explain the change in behavior in the CURLINFO_OS_ERRNO doc.

- Add to the CURLINFO_OS_ERRNO doc the list of libcurl network-related
  errors that may cause the errno to be saved.

data->state.os_errno is saved before libcurl returns a network-related
failure such as connection failure. It is accessible to the user via
CURLINFO_OS_ERRNO so they can get more information about the failure.

Prior to this change it wasn't cleared before transfer, so if a user
retrieved the saved errno it could be from a previous transfer. That is
because an errno is not always saved for network-related errors.

Closes https://github.com/curl/curl/pull/13574

2024-05-10 18:26:32 -04:00

1.6 KiB

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SPDX-License-Identifier

Title

Section

Source

See-also

Protocol

curl

CURLINFO_OS_ERRNO

libcurl

curl_easy_getinfo (3)

curl_easy_setopt (3)

All

NAME

CURLINFO_OS_ERRNO - get errno number from last connect failure

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_OS_ERRNO, long *errnop);

DESCRIPTION

Pass a pointer to a long to receive the errno variable from a connect failure. Note that the value is only set on failure, it is not reset upon a successful operation. The number is OS and system specific.

libcurl network-related errors that may have a saved errno are: CURLE_COULDNT_CONNECT, CURLE_FAILED_INIT, CURLE_INTERFACE_FAILED, CURLE_OPERATION_TIMEDOUT, CURLE_RECV_ERROR, CURLE_SEND_ERROR.

Since 8.8.0 libcurl clears the easy handle's saved errno before performing the transfer. Prior versions did not clear the saved errno, which means if a saved errno is retrieved it could be from a previous transfer on the same handle.

EXAMPLE

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    res = curl_easy_perform(curl);
    if(res != CURLE_OK) {
      long error;
      res = curl_easy_getinfo(curl, CURLINFO_OS_ERRNO, &error);
      if(!res && error) {
        printf("Errno: %ld\n", error);
      }
    }
    curl_easy_cleanup(curl);
  }
}

AVAILABILITY

Added in 7.12.2

RETURN VALUE

Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.

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