[PATCH] D42776: [Sema] Fix an assertion failure in constant expression evaluation of calls to functions with default arguments

[Akira Hatanaka via Phabricator via cfe-commits]

ahatanak added inline comments.


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Comment at: lib/AST/ExprConstant.cpp:597
+    }
+    void clearDefaultArgNum() { CurDefaultArgNum = 0; }
+    unsigned CurDefaultArgNum = 0, NextDefaultArgNum = 0;
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rsmith wrote:
> This is wrong: these scopes can nest, so you can't just reset the number to 0 when you're done. You should restore the prior number when you're done here, to divide up evaluation into CXXDefaultArgExpr scopes. (Technically, I think it would also be correct to leave the number alone when you leave one of these scopes, but only because a scope for a particular parameter's default argument can't nest within another scope for the same default argument expression -- and even that might not be true in the presence of template instantiation.)
Do you mean VisitCXXDefaultArgExpr can be called the second time before the first call returns? Do you have an example code that would cause that to happen (which I can perhaps add as a test case)?

It seemed to me that that would happen only if you used a lambda expression for the default argument, but I thought the current standard doesn't allow using lambda expressions in constant expressions.


https://reviews.llvm.org/D42776