Nuitka Release 0.5.32

This is to inform you about the new stable release of Nuitka. It is the extremely compatible Python compiler. Please see the page "What is Nuitka?" for an overview.

This release contains substantial new optimization, bug fixes, and already the full support for Python 3.7. Among the fixes, the enhanced coroutine work for compatiblity with uncompiled ones is most important.

Bug Fixes

  • Fix, was optimizing write backs of attribute in-place assignments falsely.
  • Fix, generator stop future was not properly supported. It is now the default for Python 3.7 which showed some of the flaws.
  • Python3.5: The __qualname__ of coroutines and asyncgen was wrong.
  • Python3.5: Fix, for dictionary unpackings to calls, check the keys if they are string values, and raise an exception if not.
  • Python3.6: Fix, need to check assignment unpacking for too short sequences, we were giving IndexError instead of ValueError for these. Also the error messages need to consider if they should refer to "at least" in their wording.
  • Fix, outline nodes were cloned more than necessary, which would corrupt the code generation if they later got removed, leading to a crash.
  • Python3.5: Compiled coroutines awaiting uncompiled coroutines was not working properly for finishing the uncompiled ones. Also the other way around was raising a RuntimeError when trying to pass an exception to them when they were already finished. This should resolve issues with asyncio module.
  • Fix, side effects of a detected exception raise, when they had an exception detected inside of them, lead to an infinite loop in optimization. They are now optimized in-place, avoiding an extra step later on.

New Features

  • Support for Python 3.7 with only some corner cases not supported yet.

Optimization

  • Delay creation of StopIteration exception in generator code for as long as possible. This gives more compact code for generations, which now pass the return values via compiled generator attribute for Python 3.3 or higher.
  • Python3: More immediate re-formulation of classes with no bases. Avoids noise during optimization.
  • Python2: For class dictionaries that are only assigned from values without side effects, they are not converted to temporary variable usages, allowing the normal SSA based optimization to work on them. This leads to constant values for class dictionaries of simple classes.
  • Explicit cleanup of nodes, variables, and local scopes that become unused, has been added, allowing for breaking of cyclic dependencies that prevented memory release.

Tests

  • Adapted 3.5 tests to work with 3.7 coroutine changes.
  • Added CPython 3.7 test suite.

Cleanups

  • Removed remaining code that was there for 3.2 support. All uses of version comparisons with 3.2 have been adapted. For us, Python3 now means 3.3, and we will not work with 3.2 at all. This removed a fair bit of complexity for some things, but not all that much.
  • Have dedicated file for import released helpers, so they are easier to find if necessary. Also do not have code for importing a name in the header file anymore, not performance relevant.
  • Disable Python warnings when running scons. These are particularily given when using a Python debug binary, which is happening when Nuitka is run with --python-debug option and the inline copy of Scons is used.
  • Have a factory function for all conditional statement nodes created. This solved a TODO and handles the creation of statement sequences for the branches as necessary.
  • Split class reformulation into two files, one for Python2 and one for Python3 variant. They share no code really, and are too confusing in a single file, for the huge code bodies.
  • Locals scopes now have a registry, where functions and classes register their locals type, and then it is created from that.
  • Have a dedicated helper function for single argument calls in static code that does not require an array of objects as an argument.

Organizational

  • There are now requirements-devel.txt and requirements.txt files aimed at usage with scons and by users, but they are not used in installation.

Summary

This releases has this important step to add conversion of locals dictionary usages to temporary variables. It is not yet done everywhere it is possible, and the resulting temporary variables are not yet propagated in the all the cases, where it clearly is possible. Upcoming releases ought to achieve that most Python2 classes will become to use a direct dictionary creation.

Adding support for Python 3.7 is of course also a huge step. And also this happened fairly quickly and soon after its release. The generic classes it adds were the only real major new feature. It breaking the internals for exception handling was what was holding back initially, but past that, it was really easy.

Expect more optimization to come in the next releases, aiming at both the ability to predict Python3 metaclasses __prepare__ results, and at more optimization applied to variables after they became temporary variables.

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