Translate unions in unsafe#32
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nunoplopes merged 19 commits intoCpp2Rust:masterfrom Apr 28, 2026
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Rename EmitRustStruct as EmitRustStructOrUnion since the logic for emitting a struct or a union is very similar, the only thing that is really different is whether are are emitting the struct or union keyword. All structs and unions have now repr(C). The Rust compiler is allowed to reorder fields. This is undesirable for unions where order of fields is strict. Since a struct that is defined outside an union can be used inside an union, we have to be pessimstic and consider all structs as having repr(C). Unions cannot derive the Default trait, so implement Default as the 0 bit pattern, which should be enough for the current usages of union fields.
nunoplopes
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Apr 28, 2026
| if (auto *default_ctor = GetUserDefinedDefaultConstructor(cxx)) { | ||
| StrCat(keyword_unsafe_); | ||
| PushBrace unsafe_brace(*this); | ||
| Convert(clang::CXXConstructExpr::Create( |
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won't this leak memory?
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It's created inside the allocator of ASTContext, the node is automatically freed when ASTContext is destroyed
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C/C++ unions are translated as Rust unions in unsafe. They manually implement default with
std::mem::zeroedsince unions cannot derive DefaultEach struct and union is decorated with the
repr(C)attribute to make sure that the C layout is preserved. We need this because Rust is free to reorder fields for optimal struct layout