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define_aggregate: provide empty user-defined constructor or destructor for unions with non-trivial members #119

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define_aggregate: provide empty user-defined constructor or destructor for unions with non-trivial members #119

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BaLiKfromUA
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@BaLiKfromUA BaLiKfromUA commented Nov 23, 2024 •
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Issue number of the reported bug or feature request: #115

Describe your changes

Tried to implement next behaviour from paper:

[7.10] If C is a union type for which any of its members are not trivially default constructible, then D has a user-provided default constructor which has no effect.

[7.11] If C is a union type for which any of its members are not trivially destructible, then D has a user-provided destructor which has no effect.

Testing performed

  • Automated testing with type_traits
  • Manual testing via code like this
union UU;
static_assert(is_type(define_aggregate(
    ^^UU,
    {
        data_member_spec(^^int),
        data_member_spec(^^std::string),
    })));

int main() {
  UU u;
  u.~UU();
  
  return 0;
}
  • assertations in code

Additional context

N/A

@BaLiKfromUA
add failing test
a26410c 
Signed-off-by: Valentyn Yukhymenko <valentin.yukhymenko@gmail.com>
@BaLiKfromUA
fix test since I misunderstood problem
77f0d49 
Signed-off-by: Valentyn Yukhymenko <valentin.yukhymenko@gmail.com>
@BaLiKfromUA
better test
07eec9e 
Signed-off-by: Valentyn Yukhymenko <valentin.yukhymenko@gmail.com>
@BaLiKfromUA
first version of fix
c71cdd5 
Signed-off-by: Valentyn Yukhymenko <valentin.yukhymenko@gmail.com>
@BaLiKfromUA
empty body instead of explicit default
fddb4ca 
Signed-off-by: Valentyn Yukhymenko <valentin.yukhymenko@gmail.com>
@BaLiKfromUA
small refactoring
5a2a884 
Signed-off-by: Valentyn Yukhymenko <valentin.yukhymenko@gmail.com>
@BaLiKfromUA
fix bug with userProvided flag + add asserts for safety
a5e5efe 
Signed-off-by: Valentyn Yukhymenko <valentin.yukhymenko@gmail.com>
@BaLiKfromUA
small refactoring
6d4b202 
Signed-off-by: Valentyn Yukhymenko <valentin.yukhymenko@gmail.com>
@BaLiKfromUA
small refactoring
bc70064 
Signed-off-by: Valentyn Yukhymenko <valentin.yukhymenko@gmail.com>
@BaLiKfromUA
wording
a8ab620 
Signed-off-by: Valentyn Yukhymenko <valentin.yukhymenko@gmail.com>
BaLiKfromUA
BaLiKfromUA commented Nov 23, 2024
View reviewed changes
clang/lib/Sema/SemaReflect.cpp
NewDecl->needsImplicitDefaultConstructor();

if (NeedToGenerateDefaultConstr) {
S.DeclareImplicitDefaultConstructor(NewDecl);
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@BaLiKfromUA BaLiKfromUA Nov 23, 2024 •
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potentially hacky approach but I tried to reuse existing code as much as possible to not copy generation of constructors

BaLiKfromUA
BaLiKfromUA commented Nov 23, 2024
View reviewed changes
clang/lib/AST/ExprConstantMeta.cpp
@@ -4532,6 +4532,47 @@ bool define_aggregate(APValue &Result, ASTContext &C, MetaActions &Meta,
if (!Definition)
return true;

if (Definition->isUnion()) {
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decided to put this logic here instead of SemaReflect because this code is specific to function and doesn't require access to Sema

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