[clang] [clang] Allow constexpr cast from `void*` in more cases (PR #89484)
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[clang] [clang] Allow constexpr cast from `void*` in more cases (PR #89484)
https://github.com/Endilll closed https://github.com/llvm/llvm-project/pull/89484 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Allow constexpr cast from `void*` in more cases (PR #89484)
https://github.com/Endilll updated
https://github.com/llvm/llvm-project/pull/89484
>From 5985dbe47e052505278d60628bbb5ca751cc3b6c Mon Sep 17 00:00:00 2001
From: offsetof <131769984+offse...@users.noreply.github.com>
Date: Sat, 20 Apr 2024 02:35:09 +
Subject: [PATCH 1/2] [clang] Allow constexpr cast from "void*" in more cases
When converting from "cv void*" to "T*" in a constant expression, check
that the actual pointee type is similar to "T" (as opposed to requiring
that the types are the same except top-level qualifiers).
Also implement the resolution of the tentatively ready CWG issue 2819,
adding support for the case when the operand is a null pointer.
---
clang/lib/AST/ExprConstant.cpp | 7 ---
clang/test/CXX/drs/dr28xx.cpp| 8
clang/test/CXX/expr/expr.const/p5-26.cpp | 7 +++
clang/www/cxx_dr_status.html | 2 +-
4 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 73ae8d8efb23a2..d7aee8c92b83d5 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -9237,9 +9237,10 @@ bool PointerExprEvaluator::VisitCastExpr(const CastExpr
*E) {
bool HasValidResult = !Result.InvalidBase && !Result.Designator.Invalid
&&
!Result.IsNullPtr;
bool VoidPtrCastMaybeOK =
- HasValidResult &&
- Info.Ctx.hasSameUnqualifiedType(Result.Designator.getType(Info.Ctx),
- E->getType()->getPointeeType());
+ Result.IsNullPtr ||
+ (HasValidResult &&
+ Info.Ctx.hasSimilarType(Result.Designator.getType(Info.Ctx),
+ E->getType()->getPointeeType()));
// 1. We'll allow it in std::allocator::allocate, and anything which that
//calls.
// 2. HACK 2022-03-28: Work around an issue with libstdc++'s
diff --git a/clang/test/CXX/drs/dr28xx.cpp b/clang/test/CXX/drs/dr28xx.cpp
index 4d9b0c76758d53..591bf7abfd872d 100644
--- a/clang/test/CXX/drs/dr28xx.cpp
+++ b/clang/test/CXX/drs/dr28xx.cpp
@@ -10,6 +10,14 @@
// expected-no-diagnostics
#endif
+namespace cwg2819 { // cwg2819: 19 review 2023-12-01
+#if __cpp_constexpr >= 202306L
+ constexpr void* p = nullptr;
+ constexpr int* q = static_cast(p);
+ static_assert(q == nullptr);
+#endif
+}
+
namespace cwg2847 { // cwg2847: 19
#if __cplusplus >= 202002L
diff --git a/clang/test/CXX/expr/expr.const/p5-26.cpp
b/clang/test/CXX/expr/expr.const/p5-26.cpp
index 3624b1e5a3e3df..7513b11c09aa01 100644
--- a/clang/test/CXX/expr/expr.const/p5-26.cpp
+++ b/clang/test/CXX/expr/expr.const/p5-26.cpp
@@ -37,3 +37,10 @@ void err() {
// cxx23-note {{cast from
'void *' is not allowed in a constant expression in C++ standards before
C++2c}} \
// cxx26-note {{cast from
'void *' is not allowed in a constant expression because the pointed object
type 'T' is not similar to the target type 'S'}}
}
+
+int* p;
+constexpr int** pp =
+constexpr void* vp = pp;
+constexpr auto cvp = static_cast(vp);
+// cxx23-error@-1 {{constant expression}}
+// cxx23-note@-2 {{cast from 'void *' is not allowed in a constant expression}}
diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index 83b71e7c122d1e..2677364065b2f2 100755
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -16722,7 +16722,7 @@ C++ defect report implementation
status
https://cplusplus.github.io/CWG/issues/2819.html;>2819
review
Cast from null pointer value in a constant expression
-Not resolved
+Not
Resolved*
https://cplusplus.github.io/CWG/issues/2820.html;>2820
>From d858d685647780659d249d64ad99e09e00c7ade0 Mon Sep 17 00:00:00 2001
From: Vlad Serebrennikov
Date: Mon, 29 Apr 2024 15:26:55 +0300
Subject: [PATCH 2/2] Fix some 'tentatively ready'-related mess introduced in
#90352
---
clang/test/CXX/drs/dr25xx.cpp | 2 +-
clang/test/CXX/drs/dr28xx.cpp | 4 +--
clang/www/cxx_dr_status.html | 52 +--
clang/www/make_cxx_dr_status | 2 +-
4 files changed, 30 insertions(+), 30 deletions(-)
diff --git a/clang/test/CXX/drs/dr25xx.cpp b/clang/test/CXX/drs/dr25xx.cpp
index 481ae09cdb77ea..8bca58f44944f7 100644
--- a/clang/test/CXX/drs/dr25xx.cpp
+++ b/clang/test/CXX/drs/dr25xx.cpp
@@ -130,7 +130,7 @@ struct D3 : B {
#endif
#if __cplusplus >= 202302L
-namespace cwg2561 { // cwg2561: no
+namespace cwg2561 { // cwg2561: no tentatively ready 2024-03-18
struct C {
constexpr C(auto) { }
};
diff --git a/clang/test/CXX/drs/dr28xx.cpp b/clang/test/CXX/drs/dr28xx.cpp
index a2248ccdce8427..be35d366bdd614 100644
--- a/clang/test/CXX/drs/dr28xx.cpp
+++ b/clang/test/CXX/drs/dr28xx.cpp
@@ -10,7 +10,7 @@
// expected-no-diagnostics
#endif
-namespace cwg2819 { // cwg2819: 19 review 2023-12-01
+namespace
[clang] [clang] Allow constexpr cast from `void*` in more cases (PR #89484)
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[clang] [clang] Allow constexpr cast from `void*` in more cases (PR #89484)
offsetof wrote: Yes, that would be great, thank you. https://github.com/llvm/llvm-project/pull/89484 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Allow constexpr cast from `void*` in more cases (PR #89484)
https://github.com/cor3ntin approved this pull request. LGTM, thanks! https://github.com/llvm/llvm-project/pull/89484 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Allow constexpr cast from `void*` in more cases (PR #89484)
llvmbot wrote:
@llvm/pr-subscribers-clang
Author: None (offsetof)
Changes
[[expr.const]/5.14](https://eel.is/c++draft/expr.const#5.14) says that
constexpr cast from code*cv* void\*/code to `T*` is OK if the
pointee type is similar to `T`, but Clang currently only permits the conversion
if the types are the same except top-level cv-qualifiers.
This patch also allows casting `(void*)nullptr`, implementing the resolution of
[CWG2819](https://cplusplus.github.io/CWG/issues/2819).
---
Full diff: https://github.com/llvm/llvm-project/pull/89484.diff
4 Files Affected:
- (modified) clang/lib/AST/ExprConstant.cpp (+4-3)
- (modified) clang/test/CXX/drs/dr28xx.cpp (+8)
- (modified) clang/test/CXX/expr/expr.const/p5-26.cpp (+7)
- (modified) clang/www/cxx_dr_status.html (+1-1)
``diff
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 73ae8d8efb23a2..d7aee8c92b83d5 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -9237,9 +9237,10 @@ bool PointerExprEvaluator::VisitCastExpr(const CastExpr
*E) {
bool HasValidResult = !Result.InvalidBase && !Result.Designator.Invalid
&&
!Result.IsNullPtr;
bool VoidPtrCastMaybeOK =
- HasValidResult &&
- Info.Ctx.hasSameUnqualifiedType(Result.Designator.getType(Info.Ctx),
- E->getType()->getPointeeType());
+ Result.IsNullPtr ||
+ (HasValidResult &&
+ Info.Ctx.hasSimilarType(Result.Designator.getType(Info.Ctx),
+ E->getType()->getPointeeType()));
// 1. We'll allow it in std::allocator::allocate, and anything which that
//calls.
// 2. HACK 2022-03-28: Work around an issue with libstdc++'s
diff --git a/clang/test/CXX/drs/dr28xx.cpp b/clang/test/CXX/drs/dr28xx.cpp
index 4d9b0c76758d53..591bf7abfd872d 100644
--- a/clang/test/CXX/drs/dr28xx.cpp
+++ b/clang/test/CXX/drs/dr28xx.cpp
@@ -10,6 +10,14 @@
// expected-no-diagnostics
#endif
+namespace cwg2819 { // cwg2819: 19 review 2023-12-01
+#if __cpp_constexpr >= 202306L
+ constexpr void* p = nullptr;
+ constexpr int* q = static_cast(p);
+ static_assert(q == nullptr);
+#endif
+}
+
namespace cwg2847 { // cwg2847: 19
#if __cplusplus >= 202002L
diff --git a/clang/test/CXX/expr/expr.const/p5-26.cpp
b/clang/test/CXX/expr/expr.const/p5-26.cpp
index 3624b1e5a3e3df..7513b11c09aa01 100644
--- a/clang/test/CXX/expr/expr.const/p5-26.cpp
+++ b/clang/test/CXX/expr/expr.const/p5-26.cpp
@@ -37,3 +37,10 @@ void err() {
// cxx23-note {{cast from
'void *' is not allowed in a constant expression in C++ standards before
C++2c}} \
// cxx26-note {{cast from
'void *' is not allowed in a constant expression because the pointed object
type 'T' is not similar to the target type 'S'}}
}
+
+int* p;
+constexpr int** pp =
+constexpr void* vp = pp;
+constexpr auto cvp = static_cast(vp);
+// cxx23-error@-1 {{constant expression}}
+// cxx23-note@-2 {{cast from 'void *' is not allowed in a constant expression}}
diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index 83b71e7c122d1e..2677364065b2f2 100755
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -16722,7 +16722,7 @@ C++ defect report implementation
status
https://cplusplus.github.io/CWG/issues/2819.html;>2819
review
Cast from null pointer value in a constant expression
-Not resolved
+Not
Resolved*
https://cplusplus.github.io/CWG/issues/2820.html;>2820
``
https://github.com/llvm/llvm-project/pull/89484
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[clang] [clang] Allow constexpr cast from `void*` in more cases (PR #89484)
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[clang] [clang] Allow constexpr cast from `void*` in more cases (PR #89484)
https://github.com/offsetof created
https://github.com/llvm/llvm-project/pull/89484
[[expr.const]/5.14](https://eel.is/c++draft/expr.const#5.14) says that
constexpr cast from *cv* void\* to `T*` is OK if the pointee type
is similar to `T`, but Clang currently only permits the conversion if the types
are the same except top-level cv-qualifiers.
This patch also allows casting `(void*)nullptr`, implementing the resolution of
[CWG2819](https://cplusplus.github.io/CWG/issues/2819).
>From 5985dbe47e052505278d60628bbb5ca751cc3b6c Mon Sep 17 00:00:00 2001
From: offsetof <131769984+offse...@users.noreply.github.com>
Date: Sat, 20 Apr 2024 02:35:09 +
Subject: [PATCH] [clang] Allow constexpr cast from "void*" in more cases
When converting from "cv void*" to "T*" in a constant expression, check
that the actual pointee type is similar to "T" (as opposed to requiring
that the types are the same except top-level qualifiers).
Also implement the resolution of the tentatively ready CWG issue 2819,
adding support for the case when the operand is a null pointer.
---
clang/lib/AST/ExprConstant.cpp | 7 ---
clang/test/CXX/drs/dr28xx.cpp| 8
clang/test/CXX/expr/expr.const/p5-26.cpp | 7 +++
clang/www/cxx_dr_status.html | 2 +-
4 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 73ae8d8efb23a2..d7aee8c92b83d5 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -9237,9 +9237,10 @@ bool PointerExprEvaluator::VisitCastExpr(const CastExpr
*E) {
bool HasValidResult = !Result.InvalidBase && !Result.Designator.Invalid
&&
!Result.IsNullPtr;
bool VoidPtrCastMaybeOK =
- HasValidResult &&
- Info.Ctx.hasSameUnqualifiedType(Result.Designator.getType(Info.Ctx),
- E->getType()->getPointeeType());
+ Result.IsNullPtr ||
+ (HasValidResult &&
+ Info.Ctx.hasSimilarType(Result.Designator.getType(Info.Ctx),
+ E->getType()->getPointeeType()));
// 1. We'll allow it in std::allocator::allocate, and anything which that
//calls.
// 2. HACK 2022-03-28: Work around an issue with libstdc++'s
diff --git a/clang/test/CXX/drs/dr28xx.cpp b/clang/test/CXX/drs/dr28xx.cpp
index 4d9b0c76758d53..591bf7abfd872d 100644
--- a/clang/test/CXX/drs/dr28xx.cpp
+++ b/clang/test/CXX/drs/dr28xx.cpp
@@ -10,6 +10,14 @@
// expected-no-diagnostics
#endif
+namespace cwg2819 { // cwg2819: 19 review 2023-12-01
+#if __cpp_constexpr >= 202306L
+ constexpr void* p = nullptr;
+ constexpr int* q = static_cast(p);
+ static_assert(q == nullptr);
+#endif
+}
+
namespace cwg2847 { // cwg2847: 19
#if __cplusplus >= 202002L
diff --git a/clang/test/CXX/expr/expr.const/p5-26.cpp
b/clang/test/CXX/expr/expr.const/p5-26.cpp
index 3624b1e5a3e3df..7513b11c09aa01 100644
--- a/clang/test/CXX/expr/expr.const/p5-26.cpp
+++ b/clang/test/CXX/expr/expr.const/p5-26.cpp
@@ -37,3 +37,10 @@ void err() {
// cxx23-note {{cast from
'void *' is not allowed in a constant expression in C++ standards before
C++2c}} \
// cxx26-note {{cast from
'void *' is not allowed in a constant expression because the pointed object
type 'T' is not similar to the target type 'S'}}
}
+
+int* p;
+constexpr int** pp =
+constexpr void* vp = pp;
+constexpr auto cvp = static_cast(vp);
+// cxx23-error@-1 {{constant expression}}
+// cxx23-note@-2 {{cast from 'void *' is not allowed in a constant expression}}
diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index 83b71e7c122d1e..2677364065b2f2 100755
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -16722,7 +16722,7 @@ C++ defect report implementation
status
https://cplusplus.github.io/CWG/issues/2819.html;>2819
review
Cast from null pointer value in a constant expression
-Not resolved
+Not
Resolved*
https://cplusplus.github.io/CWG/issues/2820.html;>2820
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