https://github.com/tbaederr created https://github.com/llvm/llvm-project/pull/159599
Allow side effects and mutation of local variables in the argument of a `__builtin_constant_p` call. This aligns clang's behavior with GCC's current behavior: https://godbolt.org/z/8xhMxY6rx >From 893e7137688f1cecac59da3eaec789ecd8a1056c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbae...@redhat.com> Date: Thu, 18 Sep 2025 17:50:18 +0200 Subject: [PATCH] asdf --- clang/lib/AST/ExprConstant.cpp | 7 +----- .../test/AST/ByteCode/builtin-constant-p.cpp | 6 ++--- clang/test/SemaCXX/builtin-constant-p.cpp | 22 +++++-------------- 3 files changed, 9 insertions(+), 26 deletions(-) diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp index bea592d04c2df..ae53e921ffe8c 100644 --- a/clang/lib/AST/ExprConstant.cpp +++ b/clang/lib/AST/ExprConstant.cpp @@ -4566,13 +4566,8 @@ static CompleteObject findCompleteObject(EvalInfo &Info, const Expr *E, // // FIXME: Not all local state is mutable. Allow local constant subobjects // to be read here (but take care with 'mutable' fields). - unsigned VisibleDepth = Depth; - if (llvm::isa_and_nonnull<ParmVarDecl>( - LVal.Base.dyn_cast<const ValueDecl *>())) - ++VisibleDepth; if ((Frame && Info.getLangOpts().CPlusPlus14 && - Info.EvalStatus.HasSideEffects) || - (isModification(AK) && VisibleDepth < Info.SpeculativeEvaluationDepth)) + Info.EvalStatus.HasSideEffects)) return CompleteObject(); return CompleteObject(LVal.getLValueBase(), BaseVal, BaseType); diff --git a/clang/test/AST/ByteCode/builtin-constant-p.cpp b/clang/test/AST/ByteCode/builtin-constant-p.cpp index 315a907949c34..3f0f203735640 100644 --- a/clang/test/AST/ByteCode/builtin-constant-p.cpp +++ b/clang/test/AST/ByteCode/builtin-constant-p.cpp @@ -103,8 +103,7 @@ constexpr int mutate1() { int m = __builtin_constant_p(++n); return n * 10 + m; } -static_assert(mutate1() == 21); // ref-error {{static assertion failed}} \ - // ref-note {{evaluates to '10 == 21'}} +static_assert(mutate1() == 21); /// Similar for this. GCC agrees with the bytecode interpreter. constexpr int mutate_param(bool mutate, int ¶m) { @@ -119,8 +118,7 @@ constexpr int mutate6(bool mutate) { return n * 10 + m; } static_assert(mutate6(false) == 11); -static_assert(mutate6(true) == 21); // ref-error {{static assertion failed}} \ - // ref-note {{evaluates to '10 == 21'}} +static_assert(mutate6(true) == 21); #define fold(x) (__builtin_constant_p(x) ? (x) : (x)) void g() { diff --git a/clang/test/SemaCXX/builtin-constant-p.cpp b/clang/test/SemaCXX/builtin-constant-p.cpp index 71c38c5c63c71..af56a805bd0d4 100644 --- a/clang/test/SemaCXX/builtin-constant-p.cpp +++ b/clang/test/SemaCXX/builtin-constant-p.cpp @@ -61,25 +61,14 @@ static_assert(bcp(int_to_ptr(123))); // GCC rejects these due to not recogn static_assert(bcp_fold(int_to_ptr(123))); // the bcp conditional in 'int_to_ptr' ... static_assert(__builtin_constant_p((int*)123)); // ... but GCC accepts this -// State mutations in the operand are not permitted. -// -// The rule GCC uses for this is not entirely understood, but seems to depend -// in some way on what local state is mentioned in the operand of -// __builtin_constant_p and where. -// -// We approximate GCC's rule by evaluating the operand in a speculative -// evaluation context; only state created within the evaluation can be -// modified. +// State mutations in the operand are permitted. constexpr int mutate1() { int n = 1; int m = __builtin_constant_p(++n); return n * 10 + m; } -static_assert(mutate1() == 10); +static_assert(mutate1() == 21); -// FIXME: GCC treats this as being non-constant because of the "n = 2", even -// though evaluation in the context of the enclosing constant expression -// succeeds without mutating any state. constexpr int mutate2() { int n = 1; int m = __builtin_constant_p(n ? n + 1 : n = 2); @@ -107,8 +96,6 @@ constexpr int mutate4() { } static_assert(mutate4() == 11); -// FIXME: GCC treats this as being non-constant because of something to do with -// the 'n' in the argument to internal_mutation. constexpr int mutate5() { int n = 1; int m = __builtin_constant_p(n ? internal_mutation(n) : 0); @@ -130,7 +117,7 @@ constexpr int mutate6(bool mutate) { // No mutation of state outside __builtin_constant_p: evaluates to true. static_assert(mutate6(false) == 11); // Mutation of state outside __builtin_constant_p: evaluates to false. -static_assert(mutate6(true) == 10); +static_assert(mutate6(true) == 21); // GCC strangely returns true for the address of a type_info object, despite it // not being a pointer to the start of a string literal. @@ -151,6 +138,9 @@ namespace dtor_side_effect { } #if __cplusplus >= 202002L + +static_assert(__builtin_constant_p((delete new int, 0))); // expected-error {{failed}} + namespace constexpr_dtor { struct A { int *p; _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
