https://github.com/Endilll created
https://github.com/llvm/llvm-project/pull/100572
`__is_layout_compatible` was added in Clang 19 (#81506), and at that time it
wasn't entirely clear whether it should be a revertible type trait or not. We
decided to follow the example of other type traits. Since then #95969 happened,
and now we know that we don't want new revertible type traits.
This patch removes `__is_layout_compatible` from revertible type traits list,
and leaves a comment what revertible type traits are, and that new type traits
should not be added there.
The intention is to also cherry-pick this to 19 branch.
>From 21e50b62f14461dcb6c19593b3d21c3e97209b58 Mon Sep 17 00:00:00 2001
From: Vlad Serebrennikov <serebrennikov.vladis...@gmail.com>
Date: Thu, 25 Jul 2024 16:32:46 +0300
Subject: [PATCH] [clang] Remove `__is_layout_compatible` from revertible type
traits list
---
clang/lib/Parse/ParseExpr.cpp | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index 0a017ae79de75..e82b565272831 100644
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -763,6 +763,9 @@ class CastExpressionIdValidator final : public
CorrectionCandidateCallback {
bool Parser::isRevertibleTypeTrait(const IdentifierInfo *II,
tok::TokenKind *Kind) {
if (RevertibleTypeTraits.empty()) {
+// Revertible type trait is a feature for backwards compatibility with older
+// standard libraries that declare their own structs with the same name as
+// the builtins listed below. New builtins should NOT be added to this list.
#define RTT_JOIN(X, Y) X##Y
#define REVERTIBLE_TYPE_TRAIT(Name)
\
RevertibleTypeTraits[PP.getIdentifierInfo(#Name)] = RTT_JOIN(tok::kw_, Name)
@@ -790,7 +793,6 @@ bool Parser::isRevertibleTypeTrait(const IdentifierInfo *II,
REVERTIBLE_TYPE_TRAIT(__is_fundamental);
REVERTIBLE_TYPE_TRAIT(__is_integral);
REVERTIBLE_TYPE_TRAIT(__is_interface_class);
- REVERTIBLE_TYPE_TRAIT(__is_layout_compatible);
REVERTIBLE_TYPE_TRAIT(__is_literal);
REVERTIBLE_TYPE_TRAIT(__is_lvalue_expr);
REVERTIBLE_TYPE_TRAIT(__is_lvalue_reference);
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