2.0.2 (2023-01-28)

  • Fix calling greenlet.settrace() with the same tracer object that was currently active. See issue 332.

  • Various compilation and standards conformance fixes. See #335, #336, #300, #302, #334.

2.0.1 (2022-11-07)

2.0.0.post0 (2022-11-03)

  • Add Programming Language :: Python :: 3.11 to the PyPI classifier metadata.

2.0.0 (2022-10-31)

  • Nothing changed yet.

2.0.0rc5 (2022-10-31)

  • Linux: Fix another group of rare crashes that could occur when shutting down an interpeter running multiple threads. See issue 325.

2.0.0rc4 (2022-10-30)

  • Linux: Fix a rare crash that could occur when shutting down an interpreter running multiple threads, when some of those threads are in greenlets making calls to functions that release the GIL.

2.0.0rc3 (2022-10-29)

  • Python 2: Fix a crash that could occur when raising an old-style instance object.

2.0.0rc2 (2022-10-28)

  • Workaround a CPython 3.8 bug that could cause the interpreter to crash during an early phase of shutdown with the message “Fatal Python error: Python memory allocator called without holding the GI.” This only impacted CPython 3.8a3 through CPython 3.9a5; the fix is only applied to CPython 3.8 releases (please don’t use an early alpha release of CPython 3.9).

2.0.0rc1 (2022-10-27)

  • Deal gracefully with greenlet switches that occur while deferred deallocation of objects is happening using CPython’s “trash can” mechanism. Previously, if a large nested container held items that switched greenlets during delayed deallocation, and that second greenlet also invoked the trash can, CPython’s internal state could become corrupt. This was visible as an assertion error in debug builds. Now, the relevant internal state is saved and restored during greenlet switches. See also gevent issue 1909.

  • Rename the C API function PyGreenlet_GET_PARENT to PyGreenlet_GetParent for consistency. The old name remains available as a deprecated alias.

2.0.0a2 (2022-03-24)

  • Fix a crash on older versions of the Windows C runtime when an unhandled C++ exception was thrown inside a greenlet by another native extension. This is a bug in that extension, and the interpreter will still abort, but at least it does so deliberately. Thanks to Kirill Smelkov. See PR 286.

  • Musllinux wheels for aarch64 are now built, tested, and uploaded to PyPI. Thanks to Alexander Piskun.

  • This version of greenlet is known to compile and pass tests on CPython 3.11.0a6. Earlier 3.11 releases will not work; later releases may or may not work. See PR 294. Special thanks to Victor Stinner, Brandt Bucher and the CPython developers.

2.0.0a1 (2022-01-20)


  • Add experimental, untested support for 64-bit Windows on ARM using MSVC. See PR 271.

  • Drop support for very old versions of GCC and MSVC.

  • Compilation now requires a compiler that either supports C++11 or has some other intrinsic way to create thread local variables; for older GCC, clang and SunStudio we use __thread, while for older MSVC we use __declspec(thread).

  • Wheels compatible with the musllinux specification are built, tested, and uploaded to PyPI for x86_64. (This was retroactively done for version 1.1.2 as well.)

  • This version of greenlet is known to compile and pass tests on CPython 3.11.0a4. Earlier or later 3.11 releases may or may not work. See PR 280. Special thanks to Brandt Bucher and the CPython developers.


  • Fix several leaks that could occur when using greenlets from multiple threads. For example, it is no longer necessary to call getcurrent() before exiting a thread to allow its main greenlet to be cleaned up. See issue 252.

  • Fix the C API PyGreenlet_Throw to perform the same error checking that the Python API greenlet.throw() does. Previously, it did no error checking.

  • Fix C++ exception handling on 32-bit Windows. This might have ramifications if you embed Python in your application and also use SEH on 32-bit windows, or if you embed Python in a C++ application. Please contact the maintainers if you have problems in this area.

    In general, C++ exception handling is expected to be better on most platforms. This work is ongoing.


  • The repr of some greenlets has changed. In particular, if the greenlet object was running in a thread that has exited, the repr now indicates that. NOTE: The repr of a greenlet is not part of the API and should not be relied upon by production code. It is likely to differ in other implementations such as PyPy.

  • Main greenlets from threads that have exited are now marked as dead.

1.1.3.post0 (2022-10-10)

  • Add musllinux (Alpine) binary wheels.


This preliminary support for Python 3.11 leaks memory. Please upgrade to greenlet 2 if you’re using Python 3.11.

1.1.3 (2022-08-25)

  • Add support for Python 3.11. Please note that Windows binary wheels are not available at this time.


This preliminary support for Python 3.11 leaks memory. Please upgrade to greenlet 2 if you’re using Python 3.11.

1.1.2 (2021-09-29)

  • Fix a potential crash due to a reference counting error when Python subclasses of greenlet.greenlet were deallocated. The crash became more common on Python 3.10; on earlier versions, silent memory corruption could result. See issue 245. Patch by fygao-wish.

  • Fix a leak of a list object when the last reference to a greenlet was deleted from some other thread than the one to which it belonged. For this to work correctly, you must call a greenlet API like getcurrent() before the thread owning the greenlet exits: this is a long-standing limitation that can also lead to the leak of a thread’s main greenlet if not called; we hope to lift this limitation. Note that in some cases this may also fix leaks of greenlet objects themselves. See issue 251.

  • Python 3.10: Tracing or profiling into a spawned greenlet didn’t work as expected. See issue 256, reported by Joe Rickerby.

1.1.1 (2021-08-06)

  • Provide Windows binary wheels for Python 3.10 (64-bit only).

  • Update Python 3.10 wheels to be built against 3.10rc1, where applicable.

1.1.0 (2021-05-06)

  • Add support for Python 3.10. Pre-built binary wheels for 3.10 are not currently available for all platforms. The greenlet ABI is different on Python 3.10 from all previous versions, but as 3.10 was never supported before, and the ABI has not changed on other Python versions, this is not considered a reason to change greenlet’s major version.

1.0.0 (2021-01-13)

  • Fix %s and %r formatting of a greenlet on Python 2. Previously it would result in a Unicode string instead of a native string. See issue 218.

  • Move continuous integration from Travis CI to Github Actions.

1.0a1 (2020-11-20)

  • Add the ability to set a greenlet’s PEP 567 contextvars context directly, by assigning to the greenlet’s gr_context attribute. This restores support for some patterns of using greenlets atop an async environment that became more challenging in 0.4.17. Thanks to Joshua Oreman, Mike bayer, and Fantix King, among others. See PR 198.

  • The repr of greenlet objects now includes extra information about its state. This is purely informative and the details are subject to change. See issue 215.

  • The greenlet module is now a package. There are no API changes, so all existing imports, including from C code, should continue to work.

  • (C API) The undocumented GREENLET_VERSION macro that defined a string giving the greenlet version is now deprecated and will not be updated.

  • (Documentation) Publish the change log to

Supported Platforms

  • Drop support for Python 2.4, 2.5, 2.6, 3.0, 3.1, 3.2 and 3.4. The project metadata now includes the python_requires data to help installation tools understand supported versions.

  • Add partial support for AIX ppc64 and IBM i. Thanks to Jesse Gorzinski and Kevin Adler. See PR 197.

Packaging Changes

  • Require setuptools to build from source.

  • Stop asking setuptools to build both .tar.gz and .zip sdists. PyPI has standardized on .tar.gz for all platforms.

  • Stop using a custom distutils command to build extensions. distutils is deprecated.

  • Remove the ability to use the deprecated command python test. Run greenlet tests with your favorite unittest-compatible test runner, e.g., python -m unittest discover greenlet.tests. See issue 185.

  • The directory layout and resulting sdists have changed. See issue 184.

  • greenlet is now always built with support for tracing and garbage collection, and, on Python 3.7 and above, support for context variables. The internal and undocumented C preprocessor macros that could be used to alter that at compile time have been removed (no combination other than the defaults was ever tested). This helps define a stable ABI.

0.4.17 (2020-09-22)

  • Support for PEP 567 ContextVars


  • Support for DEC Alpha architecture

  • Support for Python 3.9

  • Support for Python 3.10a0


  • Support for RISC-V architecture

  • Workaround a gcc bug on ppc64


  • Support for C-SKY architecture

  • Fixed support for ppc64 ABI

  • Fixed support for Python 3.7


  • Support for Python 3.7

  • Support for MinGW x64


  • Stop using trashcan api


  • Fixes for aarch64 architecture


  • Added missing files to manifest

  • Added workaround for ppc32 on Linux

  • Start building binary manylinux1 wheels


  • Fixed Windows builds


  • Added support for iOS (arm32)

  • Added support for ppc64le


  • Added a missing workaround for return 0 on mips

  • Restore compatibility with Python 2.5

  • Fixed stack switching on sparc


  • Expose _stack_saved property on greenlet objects, it may be used to introspect the amount of memory used by a saved stack, but the API is subject to change in the future

  • Added a workaround for return 0 compiler optimizations on all architectures

  • C API typo fixes


  • Fixed several bugs in greenlet C API

  • Fixed a bug in multi-threaded applications, which manifested itself with spurious “cannot switch to a different thread” exceptions

  • Fixed some crashes on arm and mips architectures


  • Fixed PyGreenlet_SetParent signature, thanks to BoonsNaibot

  • Fixed 64-bit Windows builds depending on wrong runtime dll


  • Better slp_switch performance on SPARC

  • Drop support for Python 2.3

  • Fix trashcan assertions on debug builds of Python

  • Remove deprecated -fno-tree-dominator-opts compiler switch

  • Enable switch code for SunStudio on 32-bit SunOS

  • Support for abc abstract methods in greenlet subclasses

  • Support custom directories for tests

  • Document switch tracing support


  • Add .travis.yml

  • Fix ‘err’ may be used uninitialized in this function

  • Check _MSC_VER for msvc specific code

  • Fix slp_switch on SPARC for multi-threaded environments

  • Add support for m68k


  • fix segfaults when using gcc 4.8 on amd64/x86 unix

  • try to disable certain gcc 4.8 optimizations that make greenlet crash

  • Fix greenlet on aarch64 with gcc 4.8

  • workaround segfault on SunOS/sun4v

  • Add support for Aarch64

  • Add support for x32 psABI on x86_64

  • Changed memory constraints for assembly macro for PPC Linux platforms.


  • Greenlet has an instance dictionary now, which means it can be used for implementing greenlet local storage, etc. However, this might introduce incompatibility if subclasses have __dict__ in their __slots__. Classes like that will fail, because greenlet already has __dict__ out of the box.

  • Greenlet no longer leaks memory after thread termination, as long as terminated thread has no running greenlets left at the time.

  • Add support for debian sparc and openbsd5-sparc64

  • Add support for ppc64 linux

  • Don’t allow greenlets to be copied with copy.copy/deepcopy

  • Fix arm32/thumb support

  • Restore greenlet’s parent after kill

  • Add experimental greenlet tracing


  • Use plain distutils for install command, this fixes installation of the greenlet.h header.

  • Enhanced arm32 support

  • Fix support for Linux/S390 zSeries

  • Workaround compiler bug on RHEL 3 / CentOS 3


  • Use sphinx to build documentation and publish it on

  • Prevent segfaults on openbsd 4/i386

  • Workaround gcc-4.0 not allowing to clobber rbx

  • Enhance test infrastructure

  • Fix possible compilation problems when including greenlet.h in C++ mode

  • Make the greenlet module work on x64 windows

  • Add a test for greenlet C++ exceptions

  • Fix compilation on Solaris with SunStudio


  • Fix various crashes with recent gcc versions and VC90

  • Try to fix stack save/restore on arm32

  • Store and restore the threadstate on exceptions like pypy/stackless do

  • GreenletExit is now based on BaseException on Python >= 2.5

  • Switch to using PyCapsule for Python 2.7 and 3.1

  • Port for AIX on PowerPC

  • Fix the sparc/solaris header

  • Improved build dependencies patch from flub.

  • Can’t pass parent=None to greenlet.greenlet() (fixes #21)

  • Rudimentary gc support (only non-live greenlets are garbage collected though)


  • Fix reference leak when passing keyword arguments to greenlets (mbachry)

  • Updated documentation.


  • Python 3 support.

  • New C API to expose Greenlets to C Extensions.

  • greenlet.switch() now accept’s keyword arguments.

  • Fix Python crasher caused by switching to new greenlet from another thread.

  • Fix Python 2.6 crash on Windows when built with VS2009. (arigo)

  • arm32 support from stackless (Sylvain Baro)

  • Linux mips support (Thiemo Seufer)

  • MingGW GCC 4.4 support (Giovanni Bajo)

  • Fix for a threading bug (issue 40 in py lib) (arigo and ghazel)

  • Loads more unit tests, some from py lib (3 times as many as Greenlet 0.2)

  • Add documentation from py lib.

  • General code, documentation and repository cleanup (Kyle Ambroff, Jared Kuolt)