Python build fails on Mac

[dzenanz]

XCode says:

PhaseScriptExecution Generate\ Wrapping/Generators/Python/itk/ITKCommonBasePython.py /Users/dzenan.zukic/Documents/ITK-py2/build/ITKCommonPython.build/Debug/Script-56F9B3CA7CE80BA1073137B7.sh (in target 'ITKCommonPython' from project 'ITK')
    cd /Users/dzenan.zukic/Documents/ITK-git
    /bin/sh -c /Users/dzenan.zukic/Documents/ITK-py2/build/ITKCommonPython.build/Debug/Script-56F9B3CA7CE80BA1073137B7.sh

/Users/dzenan.zukic/Documents/ITK-py2/Wrapping/Typedefs/ITKCommonBase.i:946: Error: Syntax error in input(3).
Command PhaseScriptExecution failed with a nonzero exit code

The content of Script-56F9B3CA7CE80BA1073137B7.sh is:

#!/bin/sh
set -e
if test "$CONFIGURATION" = "Debug"; then :
  cd /Users/dzenan.zukic/Documents/ITK-py2/Wrapping/Typedefs/python
  /Users/dzenan.zukic/Documents/ITK-py2/Wrapping/Generators/SwigInterface/swigmacos-arm64-2024-03-26-master/bin/swig -c$
fi
if test "$CONFIGURATION" = "Release"; then :
  cd /Users/dzenan.zukic/Documents/ITK-py2/Wrapping/Typedefs/python
  /Users/dzenan.zukic/Documents/ITK-py2/Wrapping/Generators/SwigInterface/swigmacos-arm64-2024-03-26-master/bin/swig -c$
fi
if test "$CONFIGURATION" = "MinSizeRel"; then :
  cd /Users/dzenan.zukic/Documents/ITK-py2/Wrapping/Typedefs/python
  /Users/dzenan.zukic/Documents/ITK-py2/Wrapping/Generators/SwigInterface/swigmacos-arm64-2024-03-26-master/bin/swig -c$
fi
if test "$CONFIGURATION" = "RelWithDebInfo"; then :
  cd /Users/dzenan.zukic/Documents/ITK-py2/Wrapping/Typedefs/python
  /Users/dzenan.zukic/Documents/ITK-py2/Wrapping/Generators/SwigInterface/swigmacos-arm64-2024-03-26-master/bin/swig -c$
fi

This is also reported to the dashboard here. The build failures started on September 17th: https://open.cdash.org/builds/10685388

Looking at the git log around that time, nothing looks suspicious. There was an update of windows binaries for CastXML, as the closest thing to relevance.

[bradking]

Wrapping/Typedefs/ITKCommonBase.i:946: Error: Syntax error in input(3).

This error occurs because that line is:

?unknown? GetNumberOfInputs() const;

Looking at Wrapping/castxml_inputs/ITKCommonBase.xml, the ?unknown? return type goes through a bunch of typedefs and eventually arrives at

<Unimplemented id="_3084" type_class="Decltype"/>

The actual type is in the macOS SDK's <cstddef> header, and is:

using size_t = decltype(sizeof(int));

CastXML has no problem with decltype() when using --castxml-output=1. However, ITK's invocation is still using --castxml-gccxml, which doesn't support decltype.

ITK really needs to port to the modern CastXML output.

[bradking]

For reference, LLVM PR 114788 switched libc++'s <cstddef> to use decltype() to define size_t. Any build using libc++ 21 or later will have this problem, not just those that get it via the macOS SDK.

[dzenanz]

And I assume we pass --castxml-gccxml because SWIG needs GCC-style XML? @thewtex is that right?

[hjmjohnson]

And I assume we pass --castxml-gccxml because SWIG needs GCC-style XML? @thewtex is that right?

@dzenanz I am busy with other issues related to wheel generation and do not want to get further side tracked.

I think we pass the XML files through igenerator.py to generate the swig input files:

I am guessing we would need a replacement for
import pygccxml

and update the python file.

[thewtex]

pygccxml should support it per:

https://github.com/CastXML/pygccxml/blob/26f63dc1f473114f836a43c309eaf5f65e5c5554/src/pygccxml/parser/source_reader.py#L159-L170

but our (vendored) pygccxml may need updates, fixes made, etc. In ITK, --castxml-gccxml is passed in our CMakeLists.txt

CC @iMichka

[hjmjohnson]

@thewtex Thanks for the hints. I'll circle back to this in a week or so after other issues are resolved. If no one has attacked the issue by then, I'll take a swing at it.

I think the approach should be:

1: Update the ITK private pygccxml implementation with CastXML/pygccxml changes to get the correct behavior
2: continue using vendored pygccxml in igenerator.py
3: change --castxml-gccxml to --castxml-output=1