This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG9bb28a18d962: [C2x] Update 'nullptr'
implementation based on CD comments (authored by aaron.ballman).
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D148800/new/
https://reviews.llvm.org/D148800
Files:
clang/docs/ReleaseNotes.rst
clang/lib/Sema/SemaExpr.cpp
clang/test/C/C2x/n3042.c
clang/test/CodeGen/nullptr.c
clang/test/Sema/nullptr.c
clang/www/c_status.html
Index: clang/www/c_status.html
===================================================================
--- clang/www/c_status.html
+++ clang/www/c_status.html
@@ -1215,13 +1215,7 @@
<tr>
<td>Introduce the nullptr constant</td>
<td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3042.htm";>N3042</a></td>
- <td class="partial" align="center">
- <details><summary>Partial</summary>
- Parts of the implementation may be incorrect until WG14 has completed NB comment
- resolution for incompatibilities with C++ that were discovered. The major use cases
- and usage patterns should work well, though.
- </details>
- </td>
+ <td class="unreleased" align="center">Clang 17</td>
</tr>
<tr>
<td>Memory layout of unions</td>
Index: clang/test/Sema/nullptr.c
===================================================================
--- clang/test/Sema/nullptr.c
+++ clang/test/Sema/nullptr.c
@@ -16,8 +16,8 @@
p = null;
int *pi = nullptr;
pi = null;
- null = 0; // expected-error {{assigning to 'nullptr_t' from incompatible type 'int'}}
- bool b = nullptr; // expected-error {{initializing 'bool' with an expression of incompatible type 'nullptr_t'}}
+ null = 0;
+ bool b = nullptr;
// Can't convert nullptr to integral implicitly.
uintptr_t i = nullptr; // expected-error-re {{initializing 'uintptr_t' (aka '{{.*}}') with an expression of incompatible type 'nullptr_t'}}
@@ -77,6 +77,9 @@
static_assert(sizeof(nullptr_t) == sizeof(void*), "");
+static_assert(!nullptr, "");
+static_assert(!(bool){nullptr}, "");
+
static_assert(!(nullptr < nullptr), ""); // expected-error {{invalid operands to binary expression}}
static_assert(!(nullptr > nullptr), ""); // expected-error {{invalid operands to binary expression}}
static_assert( nullptr <= nullptr, ""); // expected-error {{invalid operands to binary expression}}
Index: clang/test/CodeGen/nullptr.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/nullptr.c
@@ -0,0 +1,63 @@
+// RUN: %clang_cc1 -S %s -std=c2x -emit-llvm -o - | FileCheck %s
+
+// Test that null <-> nullptr_t conversions work as expected.
+typedef typeof(nullptr) nullptr_t;
+
+nullptr_t nullptr_t_val;
+
+void bool_func(bool);
+void nullptr_func(nullptr_t);
+
+void test() {
+ // Test initialization
+ bool bool_from_nullptr_t = nullptr_t_val;
+ nullptr_t nullptr_t_from_nullptr = nullptr;
+ void *vp_from_nullptr_t = nullptr_t_val;
+ nullptr_t nullptr_t_from_vp = (void *)0;
+ nullptr_t nullptr_t_from_int = 0;
+
+ // Test assignment
+ bool_from_nullptr_t = nullptr_t_val;
+ nullptr_t_from_nullptr = nullptr;
+ vp_from_nullptr_t = nullptr_t_val;
+ nullptr_t_from_vp = (void *)0;
+ nullptr_t_from_int = 0;
+
+ // Test calls
+ bool_func(nullptr_t_from_nullptr);
+ nullptr_func(nullptr_t_from_nullptr);
+ nullptr_func(0);
+ nullptr_func((void *)0);
+ nullptr_func(nullptr);
+ nullptr_func(false);
+
+ // Allocation of locals
+ // CHECK: %[[bool_from_nullptr_t:.*]] = alloca i8, align 1
+ // CHECK: %[[nullptr_t_from_nullptr:.*]] = alloca ptr, align 8
+ // CHECK: %[[vp_from_nullptr_t:.*]] = alloca ptr, align 8
+ // CHECK: %[[nullptr_t_from_vp:.*]] = alloca ptr, align 8
+ // CHECK: %[[nullptr_t_from_int:.*]] = alloca ptr, align 8
+
+ // Initialization of locals
+ // CHECK: store i8 0, ptr %[[bool_from_nullptr_t]], align 1
+ // CHECK: store ptr null, ptr %[[nullptr_t_from_nullptr]], align 8
+ // CHECK: store ptr null, ptr %[[vp_from_nullptr_t]], align 8
+ // CHECK: store ptr null, ptr %[[nullptr_t_from_vp]], align 8
+ // CHECK: store ptr null, ptr %[[nullptr_t_from_int]], align 8
+
+ // Assignment expressions
+ // CHECK: store i8 0, ptr %[[bool_from_nullptr_t]], align 1
+ // CHECK: store ptr null, ptr %[[nullptr_t_from_nullptr]], align 8
+ // CHECK: store ptr null, ptr %[[vp_from_nullptr_t]], align 8
+ // CHECK: store ptr null, ptr %[[nullptr_t_from_vp]], align 8
+ // CHECK: store ptr null, ptr %[[nullptr_t_from_int]], align 8
+
+ // Calls
+ // CHECK: call void @bool_func(i1 noundef zeroext false)
+ // CHECK: call void @nullptr_func(ptr null)
+ // CHECK: call void @nullptr_func(ptr null)
+ // CHECK: call void @nullptr_func(ptr null)
+ // CHECK: call void @nullptr_func(ptr null)
+ // CHECK: call void @nullptr_func(ptr null)
+}
+
Index: clang/test/C/C2x/n3042.c
===================================================================
--- clang/test/C/C2x/n3042.c
+++ clang/test/C/C2x/n3042.c
@@ -1,10 +1,7 @@
// RUN: %clang_cc1 -verify -ffreestanding -Wno-unused -std=c2x %s
-/* WG14 N3042: partial
+/* WG14 N3042: full
* Introduce the nullptr constant
- *
- * Claiming partial support for this feature until the WG14 NB comments can be
- * resolved to know what the correct behavior really should be.
*/
#include <stddef.h>
@@ -21,25 +18,17 @@
void questionable_behaviors() {
nullptr_t val;
- // FIXME: This code is intended to be rejected by C and is accepted by C++.
- // We've filed an NB comment with WG14 about the incompatibility.
+ // This code is intended to be rejected by C and is accepted by C++. We filed
+ // an NB comment asking for this to be changed, but WG14 declined.
(void)(1 ? val : 0); // expected-error {{non-pointer operand type 'int' incompatible with nullptr}}
(void)(1 ? nullptr : 0); // expected-error {{non-pointer operand type 'int' incompatible with nullptr}}
- // FIXME: This code is intended to be accepted by C and is rejected by C++.
- // We're following the C++ semantics until WG14 has resolved the NB comments
- // we've filed about the incompatibility.
- _Bool another = val; // expected-error {{initializing 'bool' with an expression of incompatible type 'nullptr_t'}}
- another = val; // expected-error {{assigning to 'bool' from incompatible type 'nullptr_t'}}
- _Bool again = nullptr; // expected-error {{initializing 'bool' with an expression of incompatible type 'nullptr_t'}}
- again = nullptr; // expected-error {{assigning to 'bool' from incompatible type 'nullptr_t'}}
-
- // FIXME: This code is intended to be rejected by C and is accepted by C++.
- // We've filed an NB comment with WG14 about the incompatibility.
- val = 0; // expected-error {{assigning to 'nullptr_t' from incompatible type 'int'}}
-
- // Not accepted in C++ but might want to accept in C as a null pointer constant?
- val = (void *)0; // expected-error {{assigning to 'nullptr_t' from incompatible type 'void *'}}
+ // This code is intended to be accepted by C and is rejected by C++. We filed
+ // an NB comment asking for this to be changed, but WG14 declined.
+ _Bool another = val; // expected-warning {{implicit conversion of nullptr constant to 'bool'}}
+ another = val; // expected-warning {{implicit conversion of nullptr constant to 'bool'}}
+ _Bool again = nullptr; // expected-warning {{implicit conversion of nullptr constant to 'bool'}}
+ again = nullptr; // expected-warning {{implicit conversion of nullptr constant to 'bool'}}
}
void test() {
@@ -67,6 +56,14 @@
// How about the null pointer named constant?
&nullptr; // expected-error {{cannot take the address of an rvalue of type 'nullptr_t'}}
+ // Assignment from a null pointer constant to a nullptr_t is valid.
+ null_val = 0;
+ null_val = (void *)0;
+
+ // Assignment from a nullptr_t to a pointer is also valid.
+ typed_ptr = null_val;
+ void *other_ptr = null_val;
+
// Can it be used in all the places a scalar can be used?
if (null_val) {}
if (!null_val) {}
@@ -162,18 +159,15 @@
}
// Can we use it as a function parameter?
-void null_param(nullptr_t); // expected-note 2 {{passing argument to parameter here}}
+void null_param(nullptr_t);
void other_test() {
// Can we call the function properly?
null_param(nullptr);
- // Do we get reasonable diagnostics when we can't call the function?
- null_param((void *)0); // expected-error {{passing 'void *' to parameter of incompatible type 'nullptr_t'}}
-
- // FIXME: The paper requires this to be rejected, but it is accepted in C++.
- // This should be addressed after WG14 has processed national body comments.
- null_param(0); // expected-error {{passing 'int' to parameter of incompatible type 'nullptr_t'}}
+ // We can pass any kind of null pointer constant.
+ null_param((void *)0);
+ null_param(0);
}
@@ -182,3 +176,7 @@
// Don't warn when using nullptr with %p.
printf("%p", nullptr);
}
+
+// Ensure that conversion from a null pointer constant to nullptr_t is
+// valid in a constant expression.
+static_assert((nullptr_t){} == 0);
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -10118,6 +10118,15 @@
return Incompatible;
}
+ // Conversion to nullptr_t (C2x only)
+ if (getLangOpts().C2x && LHSType->isNullPtrType() &&
+ RHS.get()->isNullPointerConstant(Context,
+ Expr::NPC_ValueDependentIsNull)) {
+ // null -> nullptr_t
+ Kind = CK_NullToPointer;
+ return Compatible;
+ }
+
// Conversions from pointers that are not covered by the above.
if (isa<PointerType>(RHSType)) {
// T* -> _Bool
@@ -10335,12 +10344,13 @@
QualType LHSTypeAfterConversion = LHSType.getAtomicUnqualifiedType();
// C99 6.5.16.1p1: the left operand is a pointer and the right is
- // a null pointer constant.
+ // a null pointer constant <C2x>or its type is nullptr_t;</C2x>.
if ((LHSTypeAfterConversion->isPointerType() ||
LHSTypeAfterConversion->isObjCObjectPointerType() ||
LHSTypeAfterConversion->isBlockPointerType()) &&
- RHS.get()->isNullPointerConstant(Context,
- Expr::NPC_ValueDependentIsNull)) {
+ ((getLangOpts().C2x && RHS.get()->getType()->isNullPtrType()) ||
+ RHS.get()->isNullPointerConstant(Context,
+ Expr::NPC_ValueDependentIsNull))) {
if (Diagnose || ConvertRHS) {
CastKind Kind;
CXXCastPath Path;
@@ -10351,6 +10361,26 @@
}
return Compatible;
}
+ // C2x 6.5.16.1p1: the left operand has type atomic, qualified, or
+ // unqualified bool, and the right operand is a pointer or its type is
+ // nullptr_t.
+ if (getLangOpts().C2x && LHSType->isBooleanType() &&
+ RHS.get()->getType()->isNullPtrType()) {
+ // NB: T* -> _Bool is handled in CheckAssignmentConstraints, this only
+ // only handles nullptr -> _Bool due to needing an extra conversion
+ // step.
+ // We model this by converting from nullptr -> void * and then let the
+ // conversion from void * -> _Bool happen naturally.
+ if (Diagnose || ConvertRHS) {
+ CastKind Kind;
+ CXXCastPath Path;
+ CheckPointerConversion(RHS.get(), Context.VoidPtrTy, Kind, Path,
+ /*IgnoreBaseAccess=*/false, Diagnose);
+ if (ConvertRHS)
+ RHS = ImpCastExprToType(RHS.get(), Context.VoidPtrTy, Kind, VK_PRValue,
+ &Path);
+ }
+ }
// OpenCL queue_t type assignment.
if (LHSType->isQueueT() && RHS.get()->isNullPointerConstant(
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -139,6 +139,25 @@
removed, as this is no longer a GNU extension but a C2x extension. You can
use ``-Wno-c2x-extensions`` to silence the extension warning instead.
+- Updated the implementation of
+ `WG14 N3042 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3042.htm>`_
+ based on decisions reached during the WG14 CD Ballot Resolution meetings held
+ in Jan and Feb 2023. This should complete the implementation of ``nullptr``
+ and ``nullptr_t`` in C. The specific changes are:
+
+ .. code-block:: c
+
+ void func(nullptr_t);
+ func(0); // Previously required to be rejected, is now accepted.
+ func((void *)0); // Previously required to be rejected, is now accepted.
+
+ nullptr_t val;
+ val = 0; // Previously required to be rejected, is now accepted.
+ val = (void *)0; // Previously required to be rejected, is now accepted.
+
+ bool b = nullptr; // Was incorrectly rejected by Clang, is now accepted.
+
+
Non-comprehensive list of changes in this release
-------------------------------------------------
- Clang now saves the address of ABI-indirect function parameters on the stack,
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