04 January 2014

Nuitka Release 0.5.0

This is to inform you about the new stable release of Nuitka. It is the extremely compatible Python compiler, “download now”.

This release breaks interface compatibility, therefore the major version number change. Also “standalone mode” has seen significant improvements on both Windows, and Linux. Should work much better now.

But consider that this part of Nuitka is still in its infancy. As it is not the top priority of mine for Nuitka, which primarily is intended as an super compatible accelerator of Python, it will continue to evolve nearby.

There is also many new optimization based on structural improvements in the direction of actual SSA.

Bug Fixes

The “standalone mode” was not working on all Redhat, Fedora, and openSUSE platforms and gave warnings with older compilers. Fixed in 0.4.7.1 already.
The “standalone mode” was not including all useful encodings. Fixed in 0.4.7.2 already.
The “standalone mode” was defaulting to --python-flag=-S which disables the parsing of “site” module. That unfortunately made it necessary to reach some modules without modifying PYTHONPATH which conflicts with the “out-of-the-box” experience.
The “standalone mode” is now handling packages properly and generally working on Windows as well.
The syntax error of having an all catching except clause and then a more specific one wasn’t causing a SyntaxError with Nuitka.
```
try:
    something()
except:
    somehandling()
except TypeError:
    notallowed()
```
A corruption bug was identified, when re-raising exceptions, the top entry of the traceback was modified after usage. Depending on malloc this was potentially causing an endless loop when using it for output.

New Features

Windows: The “standalone” mode now properly detects used DLLs using Dependency Walker which it offers to download and extra for you.
It is used as a replacement to ldd on Linux when building the binary, and as a replacement of strace on Linux when running the tests to check that nothing is loaded from the outside.

Optimization

When iterating over list, set, this is now automatically lowered to tuples avoiding the mutable container types.
So the following code is now equivalent:
```
for x in [a, b, c]:
    ...

# same as
for x in (a, b, c):
    ...
```
For constants, this is even more effective, because for mutable constants, no more is it necessary to make a copy.
Python2: The iteration of large range is now automatically lowered to xrange which is faster to loop over, and more memory efficient.
Added support for the xrange built-in.
The statement only expression optimization got generalized and now is capable of removing useless parts of operations, not only the whole thing when it has not side effects.
```
[a, b]

# same as
a
b
```
This works for all container types.
Another example is type built-in operation with single argument. When the result is not used, it need not be called.
```
type(a)

# same as
a
```
And another example is and is not have no effect of their own as well, therefore:
```
a is b

# same as
a
b
```
Added proper handling of conditional expression branches in SSA based optimization. So far these branches were ignored, which only acceptable for temporary variables as created by tree building, but not other variable types. This is preparatory for introducing SSA for local variables.

Organizational

The option --exe is now ignored and creating an executable is the default behavior of nuitka, a new option --module allows to produce extension modules.
The binary nuitka-python was removed, and is replaced by nuitka-run with now only implies --execute on top of what nuitka is.
Using dedicated Buildbot for continuous integration testing and release creation as well.
The Downloads now offers MSI files for Win64 as well.
Discontinued the support for cross compilation to Win32. That was too limited and the design choice is to have a running CPython instance of matching architecture at Nuitka compile time.

New Tests

Expanded test coverage for “standalone mode” demonstrating usage of “hex” encoding, and PySide package.

Summary

The “executable by default” interface change improves on the already high ease of use. The new optimization do not give all that much in terms of numbers, but are all signs of structural improvements, and it is steadily approaching the point, where the really interesting stuff will happen.

The progress for standalone mode is of course significant. It is still not quite there yet, but it is making quick progress now. This will attract a lot of attention hopefully.

As for optimization, the focus for it has shifted to making exception handlers work optimal by default (publish the exception to sys.exc_info() and create traceback only when necessary) and be based on standard branches. Removing special handling of exception handlers, will be the next big step. This release includes some correctness fixes stemming from that work already.

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