Author: Eli Friedman Date: 2025-06-03T09:51:37-07:00 New Revision: 97885213bd4507b204b050c3cd570e365d21cc7d
URL: https://github.com/llvm/llvm-project/commit/97885213bd4507b204b050c3cd570e365d21cc7d DIFF: https://github.com/llvm/llvm-project/commit/97885213bd4507b204b050c3cd570e365d21cc7d.diff LOG: [clang] Don't evaluate the initializer of constexpr-unknown parameters. (#142498) If we see a parameter of reference type that isn't part of the frame, don't try to evaluate its default argument. Just treat it as a constexpr-unknown value. Fixes #141114. Fixes #141858. Added: Modified: clang/lib/AST/ExprConstant.cpp clang/test/SemaCXX/constant-expression-p2280r4.cpp Removed: ################################################################################ diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp index b20e2690d0eee..ab964e592de80 100644 --- a/clang/lib/AST/ExprConstant.cpp +++ b/clang/lib/AST/ExprConstant.cpp @@ -3550,7 +3550,12 @@ static bool evaluateVarDeclInit(EvalInfo &Info, const Expr *E, // should begin within the evaluation of E // Used to be C++20 [expr.const]p5.12.2: // ... its lifetime began within the evaluation of E; - if (isa<ParmVarDecl>(VD) && !AllowConstexprUnknown) { + if (isa<ParmVarDecl>(VD)) { + if (AllowConstexprUnknown) { + Result = &Info.CurrentCall->createConstexprUnknownAPValues(VD, Base); + return true; + } + // Assume parameters of a potential constant expression are usable in // constant expressions. if (!Info.checkingPotentialConstantExpression() || diff --git a/clang/test/SemaCXX/constant-expression-p2280r4.cpp b/clang/test/SemaCXX/constant-expression-p2280r4.cpp index c14250a268f6c..50637917ba210 100644 --- a/clang/test/SemaCXX/constant-expression-p2280r4.cpp +++ b/clang/test/SemaCXX/constant-expression-p2280r4.cpp @@ -250,3 +250,15 @@ namespace uninit_reference_used { // expected-note {{in call to 'g5()'}} } + +namespace param_reference { + constexpr int arbitrary = -12345; + constexpr void f(const int &x = arbitrary) { // expected-note {{declared here}} + constexpr const int &v1 = x; // expected-error {{must be initialized by a constant expression}} \ + // expected-note {{reference to 'x' is not a constant expression}} + constexpr const int &v2 = (x, arbitrary); // expected-warning {{left operand of comma operator has no effect}} + constexpr int v3 = x; // expected-error {{must be initialized by a constant expression}} + static_assert(x==arbitrary); // expected-error {{static assertion expression is not an integral constant expression}} + static_assert(&x - &x == 0); + } +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
