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Member initializers are ignored when checking for default constructors #816

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bsilver8192 opened this issue Feb 19, 2022 · 2 comments
Open

Member initializers are ignored when checking for default constructors #816

bsilver8192 opened this issue Feb 19, 2022 · 2 comments
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bug Something isn't working good first issue Good for newcomers

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@bsilver8192
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Expected Behavior

If members of types without default constructors have default initializers, they should not prevent treating a class as though it has a default constructor, when the default constructor is defaulted (implicitly or explicitly).

Actual Behavior

Only the types of member variables are examined.

I'm working on implementing more complete logic for detecting types with default constructors, but this needs more information from bindgen (see #124) so I'm going to leave it for now.
@bsilver8192
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Workaround with minimal change on the C++ side: define an explicit default constructor (either = default or with an empty body). There might be some subtle changes in the behavior of that in C++, but I think they're all pretty esoteric.

If #815 is fixed before this, then = default will prevent autocxx from using that default constructor.

@adetaylor adetaylor added the bug Something isn't working label Feb 24, 2022
bsilver8192 added a commit to bsilver8192/autocxx that referenced this issue Feb 27, 2022
@bsilver8192
Implement most of the C++ special member function rules
64297d8 
This now tracks most of the information about which C++ special member
functions are implicit/explicit/deleted/etc for most of the common
cases. This information was needed in several places, which were each
using different approximations that failed in different ways, so unify
those to get it all working. Also add a bunch of tests around the
various cases to keep this working.

This assumes that any non-analyzed types (except some built-in ones
which are handled specially) have no implicit special member functions,
instead of the previous behavior which assumed they all existed if the
analyzed type had explicit declarations. This should generate
functional code for more situations, but it will skip some optional
things (such as moveit traits and make_unique) for additional types. If
you run into issues with those things disappearing after this change,
make sure all dependencies of the type (superclasses and member types)
have a `generate!`/`generate_pod!`.

Added TODOs for the following unhandled parts:
* google#815 (this is a Clang warning anyways, TODOs show all
  the places to change to fix it)
* google#816 (this just means we ignore some implicit
  constructors which do exist)

Also added TODOs related to the followig issues, which limit what can be
tested but aren't made better or worse by this change:
* google#832 (this one affects lots of areas)
* google#829 (this one's pretty prone to unexpected behavior)

Also fixed some existing bugs which are surfaced by generating more
trait implementations for types in the existing tests:
* Use the correct C++ name for destructors of nested types
* Handle trait methods for types that end up ignored
@bsilver8192 bsilver8192 mentioned this issue Feb 27, 2022
Merged
2 tasks
bsilver8192 added a commit to bsilver8192/autocxx that referenced this issue Feb 28, 2022
@bsilver8192
Implement most of the C++ special member function rules
8943de2 
This now tracks most of the information about which C++ special member
functions are implicit/explicit/deleted/etc for most of the common
cases. This information was needed in several places, which were each
using different approximations that failed in different ways, so unify
those to get it all working. Also add a bunch of tests around the
various cases to keep this working.

This assumes that any non-analyzed types (except some built-in ones
which are handled specially) have no implicit special member functions,
instead of the previous behavior which assumed they all existed if the
analyzed type had explicit declarations. This should generate
functional code for more situations, but it will skip some optional
things (such as moveit traits and make_unique) for additional types. If
you run into issues with those things disappearing after this change,
make sure all dependencies of the type (superclasses and member types)
have a `generate!`/`generate_pod!`.

Added TODOs for the following unhandled parts:
* google#815 (this is a Clang warning anyways, TODOs show all
  the places to change to fix it)
* google#816 (this just means we ignore some implicit
  constructors which do exist)

Also added TODOs related to the followig issues, which limit what can be
tested but aren't made better or worse by this change:
* google#832 (this one affects lots of areas)
* google#829 (this one's pretty prone to unexpected behavior)

Also fixed some existing bugs which are surfaced by generating more
trait implementations for types in the existing tests:
* Use the correct C++ name for destructors of nested types
* Handle trait methods for types that end up ignored
@adetaylor
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Next step here is to add a failing test. Marking 'good first issue' for anyone who wants to do that.

@adetaylor adetaylor added the good first issue Good for newcomers label Apr 2, 2023
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@adetaylor @bsilver8192