# PyPy 1.4.1

We're pleased to announce the 1.4.1 release of PyPy. This release consolidates all the bug fixes that occurred since the previous release. To everyone that took the trouble to report them, we want to say thank you.

> https://pypy.org/download.html

## What is PyPy

PyPy is a very compliant Python interpreter, almost a drop-in replacement for CPython. Note that it still only emulates Python 2.5 by default; the `fast-forward` branch with Python 2.7 support is slowly getting ready but will only be integrated in the next release.

In two words, the advantage of trying out PyPy instead of CPython (the default implementation of Python) is, for now, the performance. Not all programs are faster in PyPy, but we are confident that any CPU-intensive task will be much faster, at least if it runs for long enough (the JIT has a slow warm-up phase, which can take several seconds or even one minute on the largest programs).

Note again that we do support compiling and using C extension modules from CPython (`pypy setup.py install`). However, this is still an alpha feature, and the most complex modules typically fail for various reasons; others work (e.g. `PIL`) but take a serious performance hit. Also, for Mac OS X see below.

Please note also that PyPy's performance was optimized almost exclusively on Linux. It seems from some reports that on Windows as well as Mac OS X (probably for different reasons) the performance might be lower. We did not investigate much so far.

## More highlights

- We migrated to Mercurial (thanks to Ronny Pfannschmidt and Antonio Cuni) for the effort) and moved to bitbucket. The new command to check out a copy of PyPy is:

      hg clone https://bitbucket.org/pypy/pypy

- In long-running processes, the assembler generated by old JIT-compilations is now freed. There should be no more leak, however long the process runs.

- Improve a lot the performance of the `binascii` module, and of `hashlib.md5` and `hashlib.sha`.

- Made sys.setrecursionlimit() a no-op. Instead, we rely purely on the built-in stack overflow detection mechanism, which also gives you a RuntimeError -- just not at some exact recursion level.

- Fix argument processing (now e.g. `pypy -OScpass` works like it does on CPython --- if you have a clue what it does there `:-)` )

- cpyext on Mac OS X: it still does not seem to work. I get systematically a segfault in dlopen(). Contributions welcome.

- Fix two corner cases in the GC (one in minimark, one in asmgcc+JIT). This notably prevented "pypy translate.py -Ojit" from working on Windows, leading to crashes.

- Fixed a corner case in the JIT's optimizer, leading to "Fatal RPython error: AssertionError".

- Added some missing built-in functions into the 'os' module.

- Fix ctypes (it was not propagating keepalive information from c_void_p).

Cheers,

Armin Rigo, for the rest of the team