curl_multi_add_handle() returning OOM when using more than 400 handles

[jeroen]

After upgrading to curl 8.14 we see "Out of memory" errors when adding handles to a multi. This was not the case before, and I am quite sure the system is not out of memory.

#include <stdio.h>
#include <string.h>
#include <curl/curl.h>

int main(void) {
  curl_global_init(CURL_GLOBAL_DEFAULT);
  CURLM *multi_handle = curl_multi_init();
  for(int i = 0; i < 1000; i++){
    CURL *http_handle = curl_easy_init();
    int res = curl_easy_setopt(http_handle, CURLOPT_URL, "https://www.example.com/");
    if(res != CURLE_OK){
      printf("ERROR: %s\n", curl_easy_strerror(res));
    }
    int res2 = curl_multi_add_handle(multi_handle, http_handle);
    if(res2 != CURLM_OK){
      printf("ERROR: %s\n", curl_multi_strerror(res2));
    }
  }
  return 0;
}

curl/libcurl version

curl 8.14.0

operating system

MacOS 15 ARM64

[bagder]

Reproduces for me on Linux as well

[icing]

Oh, that was a stupid mistake of mine. Fix in #17475.

[jeroen]

Could we ping distro maintainers to ship this patch with curl 8.14.0? I think it's quite a bad bug.

[bagder]

I did so => https://curl.se/mail/distros-2025-05/0006.html

[jeroen]

Thanks, confirm that with this patch everything works for me again 💯