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jak-project/third-party/curl/docs/libcurl/curl_multi_timeout.md
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Alexander J. Semenuk 5d5e35fb9b fix: Windows toolchain compatibility (curl 8.21 re-vendor, endless reconfigure loop) (#4355)
## Problem

Windows builds break with a current local toolchain (Scoop LLVM 22.1.8,
CMake 4.4.0, VS 2026), in two independent ways:

1. The build stops at curl's deliberate guard: `#error "no non-blocking
method was found/used/set"` in `third-party/curl/lib/nonblock.c`.
2. From the second configure onward, `cmake --build` re-runs CMake in an
endless loop (observed 42 consecutive reconfigure cycles in a single
build). Likely the same mechanism behind the "endlessly building" VS
2026 note in `docs/setup/dev/vs.md`.

## Root cause

1. `third-party/curl/CMake/CurlTests.c` passes `int *` to
`ioctlsocket()`, whose third parameter is `u_long *`. Clang 22 promotes
`-Wincompatible-pointer-types` to a hard error in C, so the
`HAVE_IOCTLSOCKET_FIONBIO` try_compile silently fails and
`curl_config.h` never defines it. Upstream CI does not see this because
the windows-2022 runner image ships an older LLVM. GCC 14 promotes the
same warning to a hard error, which is very likely the `CurlTests.c.obj`
failure reported from MSYS2 in open-goal/jak-project#3551. Upstream curl
hit the identical problem with GCC 14 and fixed the probe in curl 8.8.0
(curl/curl#13578).
2. The root CMakeLists copies the build tree's `compile_commands.json`
into `<src>/build/` for clangd using `configure_file()`, which registers
its input as a configure dependency. CMake rewrites
`compile_commands.json` late in every generation, after
`CTestTestfile.cmake` and `cmake_install.cmake` (outputs of the same
Ninja regen rule), so once the dependency is registered the rule is
deterministically dirty and every `ninja` invocation re-runs CMake. A
pristine first configure is safe (the file does not exist yet, so the
`if(EXISTS ...)` guard skips the copy), which is why the loop looks
machine- or IDE-specific.

## Fix

1. Per review, re-vendor `third-party/curl` at the `curl-8_21_0` tag
(previously `curl-8_3_0`), which carries the upstream probe fix plus two
years of upstream development; `vendor.yaml` updated to match.
Adjustments the version jump forced:
- curl 8.15 removed the native macOS Secure Transport backend
(`CURL_USE_SECTRANSP`), so macOS now builds curl against OpenSSL like
Linux. The two macOS workflows install Homebrew `openssl@3` and export
`OPENSSL_ROOT_DIR` (keg-only), and the macOS setup docs gained the same
two lines.
- `CURL_BROTLI` / `CURL_ZSTD` switched to AUTO-detection in curl 8.10;
pinned OFF to keep the previous no-compression behavior and avoid
silently linking whatever the CI images happen to have.
- curl's new top-level `BUILD_EXAMPLES` cache option (default ON) leaked
into discord-rpc's identically named option and broke configure at a
nonexistent `examples/send-presence` directory; pinned OFF ahead of the
third-party subdirectories.

The diff is dominated by the mechanical tag-tree swap under
`third-party/curl` (linguist-vendored, collapsed in review). The
hand-written changes are `CMakeLists.txt`, the two macOS workflows,
`docs/setup/system/macos.md`, and `vendor.yaml`.
2. Swap `configure_file()` for `file(COPY ...)`: the same clangd copy
with no configure dependency registered. (`file(COPY_FILE ...
ONLY_IF_DIFFERENT)` would be cleaner still but requires CMake 3.21,
above the declared `cmake_minimum_required(VERSION 3.10)`.)

## Test plan

- [x] Fresh `cmake --preset Release-windows-clang` (LLVM 22, no cache
seeding) completes and logs `Enabled SSL backends: Schannel`; the
FIONBIO probe passes without the previous `#error`
- [x] Full Windows Release build from scratch in the branch worktree
(all 1422 targets)
- [x] goalc-test suite: 1509 passed, 0 failed
- [x] Second consecutive configure with `compile_commands.json` present:
the regen rule in `build.ninja` has no `compile_commands.json` input;
`<src>/build/compile_commands.json` is still refreshed for clangd
- [x] Repeated `ninja` invocations after a full build no longer re-run
CMake
- [x] macOS Intel and ARM CI green (first exercise of the OpenSSL
backend switch)

---

I work off a self-hosted forge, so this GitHub account is quiet; the
configure logs and ninja dirty-node traces from the investigation are
available if anyone wants the raw data.

(AI-assisted)
2026-07-27 19:19:18 -04:00

2.5 KiB
Vendored
Generated

c, SPDX-License-Identifier, Title, Section, Source, See-also, Protocol, Added-in
c SPDX-License-Identifier Title Section Source See-also Protocol Added-in
Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. curl curl_multi_timeout 3 libcurl
curl_multi_fdset (3)
curl_multi_info_read (3)
curl_multi_setopt (3)
curl_multi_socket (3)
All
7.15.4

NAME

curl_multi_timeout - how long to wait for action before proceeding

SYNOPSIS

#include <curl/curl.h>

CURLMcode curl_multi_timeout(CURLM *multi_handle, long *timeout);

DESCRIPTION

An application using the libcurl multi interface should call curl_multi_timeout(3) to figure out how long it should wait for socket actions - at most - before proceeding.

Proceeding means either doing the socket-style timeout action: call the curl_multi_socket_action(3) function with the sockfd argument set to CURL_SOCKET_TIMEOUT, or call curl_multi_perform(3) if you are using the simpler and older multi interface approach.

The timeout value returned in the long timeout_ms points to, is in number of milliseconds at this moment. If 0, it means you should proceed immediately without waiting for anything. If it returns -1, there is no timeout at all set.

An application that uses the multi_socket API should not use this function. It should instead use the CURLMOPT_TIMERFUNCTION(3) option for proper and desired behavior.

Note: if libcurl returns a -1 timeout here, it means that libcurl currently has no stored timeout value. You must not wait too long (more than a few seconds perhaps) before you call curl_multi_perform(3) again.

%PROTOCOLS%

EXAMPLE

int main(void)
{
  struct timeval timeout;
  long timeo;
  fd_set fdread;
  fd_set fdwrite;
  fd_set fdexcep;
  int maxfd = 2;
  CURLM *multi = curl_multi_init();

  curl_multi_timeout(multi, &timeo);
  if(timeo < 0)
    /* no set timeout, use a default */
    timeo = 980;

  timeout.tv_sec = timeo / 1000;
  timeout.tv_usec = (timeo % 1000) * 1000;

  /* wait for activities no longer than the set timeout */
  select(maxfd + 1, &fdread, &fdwrite, &fdexcep, &timeout);
}

TYPICAL USAGE

Call curl_multi_timeout(3), then wait for action on the sockets. Figure out which sockets to wait for by calling curl_multi_fdset(3).

When there is activity or timeout, call curl_multi_perform(3) and then loop - until all transfers are complete.

%AVAILABILITY%

RETURN VALUE

This function returns a CURLMcode indicating success or error.

CURLM_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).