[PATCH] D146358: [clang][AST] Print name instead of type when diagnosing uninitialized subobject in constexpr variables

Fri May 19 10:52:25 PDT 2023

hazohelet added a comment.

In D146358#4352792 <https://reviews.llvm.org/D146358#4352792>, @erichkeane wrote:

> In D146358#4351787 <https://reviews.llvm.org/D146358#4351787>, @hazohelet wrote:
>
>> In D146358#4350810 <https://reviews.llvm.org/D146358#4350810>, @erichkeane wrote:
>>
>>> Our downstream discovered that this causes a regression when compiling `utility` with `ast-dump`.  I've put up a minimal reproducer: https://godbolt.org/z/oaezas7Ws
>>>
>>> @hazohelet : Will you be able to look into this soon?
>>
>> Thanks for the report and the reproducer.
>> I cannot take sufficient time for about 36 hours, but I'll be able to investigate it after that.
>
> That is long enough away that I unfortunately have to revert (see 34e49d3e85a6dd03856af0fb4b7f8d8ae1f4f06a <https://reviews.llvm.org/rG34e49d3e85a6dd03856af0fb4b7f8d8ae1f4f06a>). Please note that in the LLVM project reverts are common/frequent (we have a policy of 'revert often'), and should not be taken negatively!  Please feel free to re-submit this patch with a fix/the test provided, and we'll re-review promptly!

Thanks for the revert!

It seems that the problem is around the list initializer in template variable definition.
Minimum reproducible example:
`template <typename T> constexpr T foo{};`

When the `TextNodeDumper` enabled through `-ast-dump` visits a constexpr `VarDecl` with initializer, it evaluates the `VarDecl` and prints the value if evaluation comes successful.
(https://github.com/llvm/llvm-project/blob/55903151a2a505284ce3fcd955b1d394df0b55ea/clang/lib/AST/TextNodeDumper.cpp#L1825)
The `VarDecl::evaluateValue()` does not show the notes generated during its failed evaluation. The uninitialized-subobject note is actually generated BEFORE this patch when compiling the reproducers with `-ast-dump` flag on, but is not shown to the user.
The message should not be generated here and I assume this is an internal bug that we have to fix before resubmitting this patch.

Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D146358