Author: Jason Rice Date: 2025-07-13T06:17:41+03:00 New Revision: 6f923134ddf4afc4266c4c32854d7cc2793c23a1
URL: https://github.com/llvm/llvm-project/commit/6f923134ddf4afc4266c4c32854d7cc2793c23a1 DIFF: https://github.com/llvm/llvm-project/commit/6f923134ddf4afc4266c4c32854d7cc2793c23a1.diff LOG: [Clang][P1061] Fix template arguments in local classes (#121225) In the development of P1061 (Structured Bindings Introduce a Patch), I found this bug in the template instantiation of a local class. The issue is caused by the instantiation of the original template and not the partially instantiated template. In the example (sans the fix) the instantiation uses the first template parameter from the previous instantiation and not the current one so the error hits an assertion when it is expecting an NTTP. If they were both types then it might gladly accept the type from the wrong template which is kind of scary. In the test, the reference to `i` is substituted with a placeholder AST object that represents the resolved value when instantiating `g`. However, since the old template is used, the instantiation sees an AST object that only contains the template argument index in the context of instantiating the lambda which has a type template parameter (ie auto). I question if we should use `getTemplateInstantiationPattern` at all here. Other errors involving local classes in nested templates could also be caused by the misuse of this function (because it gets the uninstantiated template). Added: clang/test/SemaCXX/local-class-template-param-crash.cpp Modified: clang/docs/ReleaseNotes.rst clang/lib/Sema/SemaTemplateInstantiate.cpp Removed: ################################################################################ diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 8f72553acfa4c..8ba493b2ca89b 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -955,6 +955,7 @@ Bug Fixes to C++ Support consistently treat the initializer as manifestly constant-evaluated. (#GH135281) - Fix a crash in the presence of invalid base classes. (#GH147186) +- Fix a crash with NTTP when instantiating local class. Bug Fixes to AST Handling ^^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp index f04b01f64b960..20bac0e56b195 100644 --- a/clang/lib/Sema/SemaTemplateInstantiate.cpp +++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp @@ -4412,8 +4412,12 @@ Sema::InstantiateClassMembers(SourceLocation PointOfInstantiation, // No need to instantiate in-class initializers during explicit // instantiation. if (Field->hasInClassInitializer() && TSK == TSK_ImplicitInstantiation) { + // Handle local classes which could have substituted template params. CXXRecordDecl *ClassPattern = - Instantiation->getTemplateInstantiationPattern(); + Instantiation->isLocalClass() + ? Instantiation->getInstantiatedFromMemberClass() + : Instantiation->getTemplateInstantiationPattern(); + DeclContext::lookup_result Lookup = ClassPattern->lookup(Field->getDeclName()); FieldDecl *Pattern = Lookup.find_first<FieldDecl>(); diff --git a/clang/test/SemaCXX/local-class-template-param-crash.cpp b/clang/test/SemaCXX/local-class-template-param-crash.cpp new file mode 100644 index 0000000000000..ffa8590eaf77d --- /dev/null +++ b/clang/test/SemaCXX/local-class-template-param-crash.cpp @@ -0,0 +1,14 @@ +// RUN: %clang_cc1 -fsyntax-only %s -verify +// expected-no-diagnostics + +template <int i> +int g() { + return [] (auto) -> int { + struct L { + int m = i; + }; + return 0; + } (42); +} + +int v = g<1>(); _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
