https://github.com/zyn0217 updated https://github.com/llvm/llvm-project/pull/87768
>From bcebf176cd078c59bca9a2301931f0ec072b66c7 Mon Sep 17 00:00:00 2001 From: Younan Zhang <zyn7...@gmail.com> Date: Fri, 5 Apr 2024 19:12:28 +0800 Subject: [PATCH] [Clang][Sema] Avoid guessing unexpanded packs' size in getFullyPackExpandedSize There has been an optimization for SizeOfPackExprs since c5452ed94, in which we overlooked a case where the template arguments were not yet formed into a PackExpansionType at the token annotation stage. This led to a problem in that a template involving such expressions may lose its nature of being dependent, causing some false-positive diagnostics. Fixes https://github.com/llvm/llvm-project/issues/84220 --- clang/docs/ReleaseNotes.rst | 1 + clang/lib/Sema/SemaTemplateVariadic.cpp | 11 ++++++++++ clang/test/SemaTemplate/alias-templates.cpp | 23 +++++++++++++++++++++ 3 files changed, 35 insertions(+) diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 28e8ddb3c41c3e..4501bf3e8fe99f 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -504,6 +504,7 @@ Bug Fixes to C++ Support - Fix crash when inheriting from a cv-qualified type. Fixes: (`#35603 <https://github.com/llvm/llvm-project/issues/35603>`_) - Fix a crash when the using enum declaration uses an anonymous enumeration. Fixes (#GH86790). +- Handled an edge case in ``getFullyPackExpandedSize`` so that we now avoid a false-positive diagnostic. (#GH84220) Bug Fixes to AST Handling ^^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/clang/lib/Sema/SemaTemplateVariadic.cpp b/clang/lib/Sema/SemaTemplateVariadic.cpp index 903fbfd18e779c..4909414c0c78d4 100644 --- a/clang/lib/Sema/SemaTemplateVariadic.cpp +++ b/clang/lib/Sema/SemaTemplateVariadic.cpp @@ -1243,6 +1243,17 @@ std::optional<unsigned> Sema::getFullyPackExpandedSize(TemplateArgument Arg) { // expanded this pack expansion into the enclosing pack if we could. if (Elem.isPackExpansion()) return std::nullopt; + // Don't guess the size of unexpanded packs. The pack within a template + // argument may have yet to be of a PackExpansion type before we see the + // ellipsis in the annotation stage. + // + // This doesn't mean we would invalidate the optimization: Arg can be an + // unexpanded pack regardless of Elem's dependence. For instance, + // A TemplateArgument that contains either a SubstTemplateTypeParmPackType + // or SubstNonTypeTemplateParmPackExpr is always considered Unexpanded, but + // the underlying TemplateArgument thereof may not. + if (Elem.containsUnexpandedParameterPack()) + return std::nullopt; } return Pack.pack_size(); } diff --git a/clang/test/SemaTemplate/alias-templates.cpp b/clang/test/SemaTemplate/alias-templates.cpp index 8d7cc6118610a0..ab5cad72faf1b7 100644 --- a/clang/test/SemaTemplate/alias-templates.cpp +++ b/clang/test/SemaTemplate/alias-templates.cpp @@ -236,6 +236,29 @@ namespace PR14858 { void test_q(int (&a)[5]) { Q<B, B, B>().f<B, B>(&a); } } +namespace PR84220 { + +template <class...> class list {}; + +template <int> struct foo_impl { + template <class> using f = int; +}; + +template <class... xs> +using foo = typename foo_impl<sizeof...(xs)>::template f<xs...>; + +// We call getFullyPackExpandedSize at the annotation stage +// before parsing the ellipsis next to the foo<xs>. This happens before +// a PackExpansionType is formed for foo<xs>. +// getFullyPackExpandedSize shouldn't determine the value here. Otherwise, +// foo_impl<sizeof...(xs)> would lose its dependency despite the template +// arguments being unsubstituted. +template <class... xs> using test = list<foo<xs>...>; + +test<int> a; + +} + namespace redecl { template<typename> using A = int; template<typename = void> using A = int; _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
