Nuitka Release 0.5.6

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

This release brings bug fixes, important new optimization, newly supported platforms, and important compatibility improvements. Progress on all fronts.

Bug Fixes

Closure taking of global variables in member functions of classes that had a class variable of the same name was binding to the class variable as opposed to the module variable.
Overwriting compiled function’s __doc__ attribute more than once could corrupt the old value, leading to crashes. Fixed in 0.5.5.2 already.

Compatibility Python2: The exec statement execfile were changing locals() was given as an argument.

def function():
    a = 1

    exec code in locals()  # Cannot change local "a".
    exec code in None  # Can change local "a"
    exec code

Previously Nuitka treated all 3 variants the same.

Compatibility: Empty branches with a condition were reduced to only the condition, but they need in fact to also check the truth value:
```
if condition:
    pass
# must be treated as
bool(condition)
# and not (bug)
condition
```
Detection of Windows virtualenv was not working properly. Fixed in 0.5.5.2 already.
Large enough constants structures are now unstreamed via marshal module, avoiding large codes being generated with no point. Fixed in 0.5.5.2 already.
Windows: Pressing CTRL-C gave two stack traces, one from the re-execution of Nuitka which was rather pointless. Fixed in 0.5.5.1 already.
Windows: Searching for virtualenv environments didn’t terminate in all cases. Fixed in 0.5.5.1 already.
During installation from PyPI with Python3 versions, there were errors given for the Python2 only scons files. Fixed in 0.5.5.3 already.
Fix, the arguments of yield from expressions could be leaked.

Fix, closure taking of a class variable could have in a sub class where the module variable was meant.

var = 1


class C:
    var = 2

    class D:
        def f():
            # was C.var, now correctly addressed top level var
            return var

Fix, setting CXX environment variable because the installed gcc has too low version, wasn’t affecting the version check at all.
Fix, on Debian/Ubuntu with hardening-wrapper installed the version check was always failing, because these report a shortened version number to Scons.

Optimization

Local variables that must be assigned also have no side effects, making use of SSA. This allows for a host of optimization to be applied to them as well, often yielding simpler access/assign code, and discovering in more cases that frames are not necessary.
Micro optimization to dict built-in for simpler code generation.

Organisational

Added support for ARM “hard float” architecture.
Added package for Ubuntu 14.10 for download.
Added package for openSUSE 13.2 for download.
Donations were used to buy a Cubox-i4 Pro. It got Debian Jessie installed on it, and will be used to run an even larger amount of tests.
Made it more clear in the user documentation that the .exe suffix is used for all platforms, and why.
Generally updated information in User Manual and Developer Manual about the optimization status.
Using Nikola 7.1 with external filters instead of our own, outdated branch for the web site.

Cleanups

PyLint clean for the first time ever. We now have a Buildbot driven test that this stays that way.
Massive indentation cleanup of keyword argument calls. We have a rule to align the keywords, but as this was done manually, it could easily get out of touch. Now with a “autoformat” tool based on RedBaron, it’s correct. Also, spacing around arguments is now automatically corrected. More to come.
For exec statements, the coping back to local variables is now an explicit node in the tree, leader to cleaner code generation, as it now uses normal variable assignment code generation.
The MaybeLocalVariables became explicit about which variable they might be, and contribute to its SSA trace as well, which was incomplete before.
Removed some cases of code duplication that were marked as TODO items. This often resulted in cleanups.
Do not use replaceWith on child nodes, that potentially were re-used during their computation.

Summary

The release is mainly the result of consolidation work. While the previous release contained many important enhancements, this is another important step towards full SSA, closing one loop whole (class variables and exec functions), as well as applying it to local variables, largely extending its use.

The amount of cleanups is tremendous, in huge part due to infrastructure problems that prevented release repeatedly. This reduces the technological debt very much.

More importantly, it would appear that now eliminating local and temporary variables that are not necessary is only a small step away. But as usual, while this may be easy to implement now, it will uncover more bugs in existing code, that we need to address before we continue.

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