https://github.com/babadany2999 created https://github.com/llvm/llvm-project/pull/213449
### Summary P2242R3 relaxed `constexpr` function requirements in C++23 to allow jump statements such as `goto` and labels inside `constexpr` functions. In `CheckConstexprFunctionStmt`, `GotoStmtClass` and `LabelStmtClass` were added, but `IndirectGotoStmtClass` (GNU computed goto) was missed. This patch adds `case Stmt::IndirectGotoStmtClass:` alongside `GotoStmtClass` in `CheckConstexprFunctionStmt`. ### Details - Before this patch, writing `goto *p;` inside a `constexpr` function resulted in `error: statement not allowed in constexpr function` because `IndirectGotoStmtClass` fell through to the `default` case in `CheckConstexprFunctionStmt`. - With this patch, indirect gotos behave identically to standard gotos in `constexpr` function bodies: - Allowed in C++23 mode. - Issued as a C++23 extension warning in earlier modes (C++11 through C++20). - Executing an indirect goto during constant evaluation continues to produce an error during evaluation, while valid runtime paths (e.g. guarded by `if consteval`) succeed. ### Test Plan - Added test case covering indirect gotos (`goto *(&&x);`) to `clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p3.cpp`. - Verified test fails without the patch and passes with the patch across all standard modes (`-std=c++11` through C++23). >From db3e8ab18e94e552c4e48dc128373c66b9551491 Mon Sep 17 00:00:00 2001 From: Baba Dan Constantin <[email protected]> Date: Sat, 1 Aug 2026 17:09:50 +0300 Subject: [PATCH] [clang][constexpr] Allow IndirectGotoStmt in constexpr functions for C++23 P2242R3 ("More Relaxed Constexpr Functions") permitted jump statements such as `goto` and labels inside `constexpr` functions starting in C++23. When handling `GotoStmtClass` and `LabelStmtClass` in `CheckConstexprFunctionStmt`, `IndirectGotoStmtClass` (GNU computed goto) was inadvertently omitted. As a result, any indirect goto inside a `constexpr` function body hit the default case in `CheckConstexprFunctionStmt` and triggered an unrecoverable hard error (`err_constexpr_body_invalid_stmt`), even when placed in unexecuted branches (e.g. behind `if consteval`). This commit adds `case Stmt::IndirectGotoStmtClass:` alongside `GotoStmtClass` so that indirect gotos are treated consistently: - Permitted in C++23 `constexpr` functions. - Allowed in earlier standard dialects (C++11/14/17/20) as a C++23 extension warning. - Evaluated properly by constant evaluation (which rejects actual compile-time execution of computed gotos if reached). Regression test added to `clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p3.cpp`. --- clang/lib/Sema/SemaDeclCXX.cpp | 1 + clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p3.cpp | 8 ++++++++ 2 files changed, 9 insertions(+) diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp index 47b01b913b428..76b3d8cca9701 100644 --- a/clang/lib/Sema/SemaDeclCXX.cpp +++ b/clang/lib/Sema/SemaDeclCXX.cpp @@ -2343,6 +2343,7 @@ CheckConstexprFunctionStmt(Sema &SemaRef, const FunctionDecl *Dcl, Stmt *S, case Stmt::LabelStmtClass: case Stmt::GotoStmtClass: + case Stmt::IndirectGotoStmtClass: if (Cxx2bLoc.isInvalid()) Cxx2bLoc = S->getBeginLoc(); for (Stmt *SubStmt : S->children()) { diff --git a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p3.cpp b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p3.cpp index 51990ee4341d2..508941ae0429d 100644 --- a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p3.cpp +++ b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p3.cpp @@ -167,6 +167,14 @@ constexpr int DisallowedStmtsCXX14_7() { int n; // beforecxx20-warning {{uninitialized variable in a constexpr function}} } +constexpr int DisallowedStmtsCXX14_8() { + return 0; // beforecxx14-note {{previous}} + // - an indirect goto statement + goto *(&&x); // beforecxx23-warning {{use of this statement in a constexpr function is a C++23 extension}} + x:; + return 0; // beforecxx14-warning {{multiple return}} +} + constexpr int ForStmt() { for (int n = 0; n < 10; ++n) {} // beforecxx14-error {{statement not allowed in constexpr function}} return 0; _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
