initializers.
This has some interesting interactions with our existing extensions to
support C99 designated initializers as an extension in C++. Those are
resolved as follows:
* We continue to permit the full breadth of C99 designated initializers
in C++, with the exception that we disallow a partial overwrite of an
initializer with a non-trivially-destructible type. (Full overwrite
is OK, because we won't run the first initializer at all.)
* The C99 extensions are disallowed in SFINAE contexts and during
overload resolution, where they could change the meaning of valid
programs.
* C++20 disallows reordering of initializers. We only check for that for
the simple cases that the C++20 rules permit (designators of the form
'.field_name =' and continue to allow reordering in other cases).
It would be nice to improve this behavior in future.
* All C99 designated initializer extensions produce a warning by
default in C++20 mode. People are going to learn the C++ rules based
on what Clang diagnoses, so it's important we diagnose these properly
by default.
* In C++ <= 17, we apply the C++20 rules rather than the C99 rules, and
so still diagnose C99 extensions as described above. We continue to
accept designated C++20-compatible initializers in C++ <= 17 silently
by default (but naturally still reject under -pedantic-errors).
This is not a complete implementation of P0329R4. In particular, that
paper introduces new non-C99-compatible syntax { .field { init } }, and
we do not support that yet.
This is based on a previous patch by Don Hinton, though I've made
substantial changes when addressing the above interactions.
Differential Revision: https://reviews.llvm.org/D59754
llvm-svn: 370544
We failed to correctly handle the 'holes' left behind by designated
initializers in VerifyOnly mode. This would result in us thinking that a
designated initialization would be valid, only to find that it is not
actually valid when we come to build it. In a +Asserts build, that would
assert, and in a -Asserts build, that would silently lose some part of
the initialization or crash.
With this change, when an InitListExpr contains any designators, we now
always build a structured list so that we can track the locations of the
'holes' that we need to go back and fill in.
We could in principle do better: we only need the structured form if
there is a designator that jumps backwards (and can otherwise check for
the holes as we progress through the initializer list), but dealing with
that turns out to be rather complicated, so it's not done as part of
this patch.
llvm-svn: 370419
has no field declaration.
This commit fixes an invalid Winitializer-overrides warning that's shown
when analyzing a second (or any after the first) instantiation of a designated
initializer. This invalid warning is fixed by making sure that a
DesignatedInitExpr is rebuilt by the tree transformer when it has a field
designator whose FieldDecl* hasn't been yet initialized. This ensures that a
different DesignatedInitExpr is processed by Sema for every instantiation, and
thus the invalid warning is avoided.
rdar://28768441
Differential Revision: https://reviews.llvm.org/D25777
llvm-svn: 284959
Richard Smith