cfilters: fix Curl_pollset_poll() return code mixup

[bagder]

Curl_conn_cf_poll did not map adjust_pollset failures to poll-style errors properly, so error codes were treated as ready events.

Found by Codex Security

[Copilot]

Pull request overview

This PR fixes an error-code mapping issue in the connection-filter polling path: Curl_conn_cf_poll() previously mixed CURLcode return values with poll-style return codes, which could cause failures from adjust_pollset to be misinterpreted as “ready events”.

Changes:

• Document poll-style return semantics for Curl_pollset_poll() and Curl_conn_cf_poll().
• Fix Curl_conn_cf_poll() to return a poll-style int result and map adjust_pollset failures to -1.
• Minor local variable cleanup/rename in Curl_pollset_poll().

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
lib/select.c	Adds return-value documentation for Curl_pollset_poll() and renames local return variable.
lib/cfilters.c	Fixes Curl_conn_cf_poll() return-code handling to avoid treating CURLcode failures as ready events.

Comments suppressed due to low confidence (1)

lib/select.c:668

• The new return-value comment doesn’t match the actual behavior: this function can also return -1 when curlx_calloc() for pfds fails (OOM), not just on poll/select errors or fd >= FD_SETSIZE (handled inside Curl_poll()). Please either update the comment to include OOM (and/or clarify that errors include allocation failures), or change the function to set an appropriate socket errno before returning -1 for allocation failures so callers get consistent diagnostics.

/*
 * Return values:
 *   -1 = system call error or fd >= FD_SETSIZE
 *    0 = timeout
 *    N = number of structures with non zero revent fields
 */
int Curl_pollset_poll(struct Curl_easy *data,
                      struct easy_pollset *ps,
                      timediff_t timeout_ms)
{
  struct pollfd *pfds;
  unsigned int i, npfds;
  int rc;

  (void)data;
  DEBUGASSERT(data);
  DEBUGASSERT(data->conn);

  if(!ps->n)
    return curlx_wait_ms(timeout_ms);

  pfds = curlx_calloc(ps->n, sizeof(*pfds));
  if(!pfds)
    return -1;

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.