XUtils

libuv

Cross-platform asynchronous I/O. [BSD]

C/C++
https://github.com/libuv/libuv

Feature highlights

  • Full-featured event loop backed by epoll, kqueue, IOCP, event ports.

  • Asynchronous TCP and UDP sockets

  • Asynchronous DNS resolution

  • Asynchronous file and file system operations

  • File system events

  • ANSI escape code controlled TTY

  • IPC with socket sharing, using Unix domain sockets or named pipes (Windows)

  • Child processes

  • Thread pool

  • Signal handling

  • High resolution clock

  • Threading and synchronization primitives

Versioning

Starting with version 1.0.0 libuv follows the semantic versioning scheme. The API change and backwards compatibility rules are those indicated by SemVer. libuv will keep a stable ABI across major releases.

The ABI/API changes can be tracked here.

Documentation

Other resources

  • LXJS 2012 talk — High-level introductory talk about libuv.
  • libuv-dox — Documenting types and methods of libuv, mostly by reading uv.h.
  • learnuv — Learn uv for fun and profit, a self guided workshop to libuv.

These resources are not handled by libuv maintainers and might be out of date. Please verify it before opening new issues.

Downloading

libuv can be downloaded either from the GitHub repository or from the downloads site.

Before verifying the git tags or signature files, importing the relevant keys is necessary. Key IDs are listed in the MAINTAINERS file, but are also available as git blob objects for easier use.

Importing a key the usual way:

$ gpg --keyserver pool.sks-keyservers.net --recv-keys AE9BC059

Importing a key from a git blob object:

$ git show pubkey-saghul | gpg --import

Verifying releases

Git tags are signed with the developer’s key, they can be verified as follows:

$ git verify-tag v1.6.1

Starting with libuv 1.7.0, the tarballs stored in the downloads site are signed and an accompanying signature file sit alongside each. Once both the release tarball and the signature file are downloaded, the file can be verified as follows:

$ gpg --verify libuv-1.7.0.tar.gz.sign

Run tests:

$ (cd build && ctest -C Debug –output-on-failure)

Install with Homebrew

$ brew install --HEAD libuv

Note to OS X users:

Make sure that you specify the architecture you wish to build for in the “ARCHS” flag. You can specify more than one by delimiting with a space (e.g. “x86_64 i386”).

Install with vcpkg

$ git clone https://github.com/microsoft/vcpkg.git
$ ./bootstrap-vcpkg.bat # for powershell
$ ./bootstrap-vcpkg.sh # for bash
$ ./vcpkg install libuv

Running tests

Some tests are timing sensitive. Relaxing test timeouts may be necessary on slow or overloaded machines:

$ env UV_TEST_TIMEOUT_MULTIPLIER=2 build/uv_run_tests # 10s instead of 5s

Run one test

The list of all tests is in test/test-list.h.

This invocation will cause the test driver to fork and execute TEST_NAME in a child process:

$ build/uv_run_tests_a TEST_NAME

This invocation will cause the test driver to execute the test in the same process:

$ build/uv_run_tests_a TEST_NAME TEST_NAME

Debugging tools

When running the test from within the test driver process (build/uv_run_tests_a TEST_NAME TEST_NAME), tools like gdb and valgrind work normally.

When running the test from a child of the test driver process (build/uv_run_tests_a TEST_NAME), use these tools in a fork-aware manner.

Fork-aware gdb

Use the follow-fork-mode setting:

$ gdb --args build/uv_run_tests_a TEST_NAME

(gdb) set follow-fork-mode child
...
Fork-aware valgrind

Use the --trace-children=yes parameter:

$ valgrind --trace-children=yes -v --tool=memcheck --leak-check=full --track-origins=yes --leak-resolution=high --show-reachable=yes --log-file=memcheck-%p.log build/uv_run_tests_a TEST_NAME

Running benchmarks

See the section on running tests. The benchmark driver is ./uv_run_benchmarks_a and the benchmarks are listed in test/benchmark-list.h.

-fno-strict-aliasing

It is recommended to turn on the -fno-strict-aliasing compiler flag in projects that use libuv. The use of ad hoc “inheritance” in the libuv API may not be safe in the presence of compiler optimizations that depend on strict aliasing.

MSVC does not have an equivalent flag but it also does not appear to need it at the time of writing (December 2019.)

z/OS Notes

z/OS compilation requires ZOSLIB to be installed. When building with [CMake][], use the flag -DZOSLIB_DIR to specify the path to ZOSLIB:

$ (cd build && cmake .. -DBUILD_TESTING=ON -DZOSLIB_DIR=/path/to/zoslib)
$ cmake --build build

z/OS creates System V semaphores and message queues. These persist on the system after the process terminates unless the event loop is closed.

Use the ipcrm command to manually clear up System V resources.

Articles

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