https://github.com/sdkrystian created https://github.com/llvm/llvm-project/pull/186200
When a non-type template parameter has a type containing an undeduced placeholder type that is invalid (e.g., a function returning a function), `SubstAutoTypeSourceInfoDependent` can return null if the type is invalid. `CheckNonTypeTemplateParameterType` was not handling this case and would dereference the null pointer. Fixes #177545 >From 046639848cbe188700b4fa9090f245de7dc62288 Mon Sep 17 00:00:00 2001 From: Krystian Stasiowski <[email protected]> Date: Mon, 26 Jan 2026 15:28:29 -0500 Subject: [PATCH 1/2] [Clang] Fix crash in CheckNonTypeTemplateParameterType with invalid type SubstAutoTypeSourceInfoDependent can return null when transforming an invalid type containing decltype(auto). Handle this case by returning QualType() to signal failure. Fixes #177545 --- clang/lib/Sema/SemaTemplate.cpp | 5 ++++- clang/test/SemaTemplate/deduction-crash.cpp | 5 +++++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp index 9b0bec20618a0..9194ee5e2bee9 100644 --- a/clang/lib/Sema/SemaTemplate.cpp +++ b/clang/lib/Sema/SemaTemplate.cpp @@ -1342,7 +1342,10 @@ QualType Sema::CheckNonTypeTemplateParameterType(TypeSourceInfo *&TSI, // - an identifier associated by name lookup with a non-type // template-parameter declared with a type that contains a // placeholder type (7.1.7.4), - TSI = SubstAutoTypeSourceInfoDependent(TSI); + TypeSourceInfo *NewTSI = SubstAutoTypeSourceInfoDependent(TSI); + if (!NewTSI) + return QualType(); + TSI = NewTSI; } return CheckNonTypeTemplateParameterType(TSI->getType(), Loc); diff --git a/clang/test/SemaTemplate/deduction-crash.cpp b/clang/test/SemaTemplate/deduction-crash.cpp index 99ca0b365ff6f..7c3e92af068e9 100644 --- a/clang/test/SemaTemplate/deduction-crash.cpp +++ b/clang/test/SemaTemplate/deduction-crash.cpp @@ -172,3 +172,8 @@ namespace PR51872_part1 { // expected-error@-1 {{no viable constructor or deduction guide for deduction of template arguments of 'T1'}} // expected-note@-7 {{candidate template ignored: could not match 'PR51872_part1::T1<value-parameter-0-0>' against 'int'}} } + +namespace GH177545 { + template<decltype(auto)()() volatile throw() -> char> // expected-error {{'decltype(auto)' can only be used as a return type in a function declaration}} + struct T2; // expected-error@-1 {{function cannot return function type 'auto () volatile throw() -> decltype(auto)'}} +} >From 4ebf3d74cc9e18aad8642a50a3c9cdd7a50ad4b8 Mon Sep 17 00:00:00 2001 From: Krystian Stasiowski <[email protected]> Date: Thu, 12 Mar 2026 13:52:27 -0400 Subject: [PATCH 2/2] [FOLD] add release note --- clang/docs/ReleaseNotes.rst | 1 + 1 file changed, 1 insertion(+) diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 3617786f09595..35e637e7290cc 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -322,6 +322,7 @@ Bug Fixes in This Version - Fixed a crash when parsing ``#pragma clang attribute`` arguments for attributes that forbid arguments. (#GH182122) - Fixed a bug with multiple-include optimization (MIOpt) state not being preserved in some cases during lexing, which could suppress header-guard mismatch diagnostics and interfere with include-guard optimization. (#GH180155) - Fixed a crash when normalizing constraints involving concept template parameters whose index coincided with non-concept template parameters in the same parameter mapping. +- Fixed a crash when substituting into a non-type template parameter that has a type containing an undeduced placeholder type. Bug Fixes to Compiler Builtins ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
