[PATCH] D82940: [ASTReader][ASTWriter][PCH][Modules] Fix (de)serialization of SwitchCases

[Gabor Marton via Phabricator via cfe-commits]

martong added a comment.

In D82940#2125183 <https://reviews.llvm.org/D82940#2125183>, @riccibruno wrote:

> > I'm not certain I understand, but I'm removing my LG while we figure it out. Can you expound a bit further?
>
> Take a look at the AST dump of a small modification of the reduced test case which doesn't trigger the assertion:
>
>   void should_not_crash_with_switch_in_lambda() {
>     switch (1)
>     default:;
>     auto f = [] {
>       switch (1)
>       default:;
>     };
>   }
>
>
> Before the serialization of `LambdaExpr` for the `LambdaExpr *E`, we have `E->getBody() == E->getCallOperator()->getBody()`.
>  After serialization this is not true anymore because we are writing and reading the body directly when visiting the `LambdaExpr`
>  (the captures have the same problem).


The same is true in case of the simplest lambda example:

  void foo() {   // line 11
      []{};
  }

The AST that we got from the Parser has only one CompoundStmt node, but referenced in the CXXMethodDecl and added as a direct child to LambdaExpr:

  `-LambdaExpr 0x5643235372c8 <line:12:5, col:8>
    |-CXXRecordDecl 0x564323536c98 <col:5> col:5 implicit class definition
    | |-CXXMethodDecl 0x564323536dd8 <col:6, col:8> col:5 constexpr operator() 'auto () const -> void' inline
    | | `-CompoundStmt 0x564323536e88 <col:7, col:8>
    `-CompoundStmt 0x564323536e88 <col:7, col:8>

After serialization and deserialization, the CompoundStmt is just copied, notice the different pointer values:

  `-LambdaExpr 0x55a49f35f830 <line:12:5, col:8>
    |-CXXRecordDecl 0x55a49f35f860 <col:5> col:5 imported implicit <undeserialized declarations> class definition
    | |-CXXMethodDecl 0x55a49f35fac8 <col:6, col:8> col:5 imported constexpr operator() 'auto () const -> void' inline
    | | `-CompoundStmt 0x55a49f360110 <col:7, col:8>
    `-CompoundStmt 0x55a49f35f820 <col:7, col:8>

This suggests that we should prepare the ASTReader/ASTWriter to be able to handle references to Stmts similarly as it can already handle references to Decls (see `ASTWriter::DeclIDs`).
Does this sound as a good direction, should I move forward this way?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D82940/new/

https://reviews.llvm.org/D82940