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Create a placement operator new directly. (#6941)

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Instead of injecting code to declare an `operator new`, generate AST for
it directly. In order to use this, directly generate a `CXXNewExpr`
rather than asking Clang to build one.

This is less of a hack, and doesn't visibly leak an `operator new`
declaration that inline C++ code or template instantiations might see.
It also avoids generating a warning in C++26 and later that the
`constexpr` declaration of `operator new` is used but not defined.

Assisted-by: Gemini 3.1 Pro via Antigravity
This commit is contained in:
Richard Smith
2026-03-20 16:50:37 +00:00
committed by GitHub
parent 8e824d02be
commit e06eb8f532
5 changed files with 120 additions and 84 deletions
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toolchain/check/testdata/interop/cpp/function/thunk_ast.carbon
Vendored
+26 -49
View File
@@ -18,55 +18,7 @@
auto foo(short a) -> void;
// CHECK:STDOUT: |-FunctionDecl {{0x[a-f0-9]+}} <./thunk_required.h:[[@LINE-1]]:1, col:22> col:6 used foo 'auto (short) -> void'
// CHECK:STDOUT: | `-ParmVarDecl {{0x[a-f0-9]+}} <col:10, col:16> col:16 a 'short'
// CHECK:STDOUT: |-NamespaceDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit std
// CHECK:STDOUT: |-FunctionDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit operator new 'void *(__size_t)'
// CHECK:STDOUT: | |-VisibilityAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit Default
// CHECK:STDOUT: | |-ReturnsNonNullAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit
// CHECK:STDOUT: | `-AllocSizeAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit 1
// CHECK:STDOUT: |-FunctionDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit operator new 'void *(__size_t, std::align_val_t)'
// CHECK:STDOUT: | |-ParmVarDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit 'std::align_val_t'
// CHECK:STDOUT: | |-VisibilityAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit Default
// CHECK:STDOUT: | |-ReturnsNonNullAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit
// CHECK:STDOUT: | |-AllocSizeAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit 1
// CHECK:STDOUT: | `-AllocAlignAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit 2
// CHECK:STDOUT: |-FunctionDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit operator new[] 'void *(__size_t)'
// CHECK:STDOUT: | |-VisibilityAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit Default
// CHECK:STDOUT: | |-ReturnsNonNullAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit
// CHECK:STDOUT: | `-AllocSizeAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit 1
// CHECK:STDOUT: |-FunctionDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit operator new[] 'void *(__size_t, std::align_val_t)'
// CHECK:STDOUT: | |-ParmVarDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit 'std::align_val_t'
// CHECK:STDOUT: | |-VisibilityAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit Default
// CHECK:STDOUT: | |-ReturnsNonNullAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit
// CHECK:STDOUT: | |-AllocSizeAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit 1
// CHECK:STDOUT: | `-AllocAlignAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit 2
// CHECK:STDOUT: |-FunctionDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit operator delete 'void (void *) noexcept'
// CHECK:STDOUT: | |-ParmVarDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit 'void *'
// CHECK:STDOUT: | `-VisibilityAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit Default
// CHECK:STDOUT: |-FunctionDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit operator delete 'void (void *, std::align_val_t) noexcept'
// CHECK:STDOUT: | |-ParmVarDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit 'void *'
// CHECK:STDOUT: | |-ParmVarDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit 'std::align_val_t'
// CHECK:STDOUT: | `-VisibilityAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit Default
// CHECK:STDOUT: | |-ParmVarDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit 'void *'
// CHECK:STDOUT: | `-VisibilityAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit Default
// CHECK:STDOUT: | |-ParmVarDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit 'void *'
// CHECK:STDOUT: | |-ParmVarDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit 'std::align_val_t'
// CHECK:STDOUT: | `-VisibilityAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit Default
// CHECK:STDOUT: |-FunctionDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit operator delete[] 'void (void *) noexcept'
// CHECK:STDOUT: | |-ParmVarDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit 'void *'
// CHECK:STDOUT: | `-VisibilityAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit Default
// CHECK:STDOUT: |-FunctionDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit operator delete[] 'void (void *, std::align_val_t) noexcept'
// CHECK:STDOUT: | |-ParmVarDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit 'void *'
// CHECK:STDOUT: | |-ParmVarDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit 'std::align_val_t'
// CHECK:STDOUT: | `-VisibilityAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit Default
// CHECK:STDOUT: | |-ParmVarDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit 'void *'
// CHECK:STDOUT: | `-VisibilityAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit Default
// CHECK:STDOUT: | |-ParmVarDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit 'void *'
// CHECK:STDOUT: | |-ParmVarDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc> implicit 'std::align_val_t'
// CHECK:STDOUT: | `-VisibilityAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit Default
// CHECK:STDOUT: |-FunctionDecl {{0x[a-f0-9]+}} <<carbon-internal>:8:1, line:14:1> line:8:7 operator new 'void *(unsigned long, void *) noexcept'
// CHECK:STDOUT: | |-ParmVarDecl {{0x[a-f0-9]+}} <<built-in>:176:23, col:37> <carbon-internal>:8:33 'unsigned long'
// CHECK:STDOUT: | `-ParmVarDecl {{0x[a-f0-9]+}} <col:35, col:39> col:40 'void *'
// CHECK:STDOUT: `-FunctionDecl {{0x[a-f0-9]+}} <./thunk_required.h:[[@LINE-51]]:6> col:6 foo__carbon_thunk 'void (short * _Nonnull)' extern
// CHECK:STDOUT: `-FunctionDecl {{0x[a-f0-9]+}} <col:6> col:6 foo__carbon_thunk 'void (short * _Nonnull)' extern
// CHECK:STDOUT: |-ParmVarDecl {{0x[a-f0-9]+}} <col:6> col:6 used a 'short * _Nonnull':'short *'
// CHECK:STDOUT: |-ReturnStmt {{0x[a-f0-9]+}} <col:6>
// CHECK:STDOUT: | `-CallExpr {{0x[a-f0-9]+}} <col:6> 'void'
@@ -78,6 +30,7 @@ auto foo(short a) -> void;
// CHECK:STDOUT: | `-DeclRefExpr {{0x[a-f0-9]+}} <col:6> 'short * _Nonnull':'short *' lvalue ParmVar {{0x[a-f0-9]+}} 'a' 'short * _Nonnull':'short *'
// CHECK:STDOUT: |-AlwaysInlineAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit always_inline
// CHECK:STDOUT: `-AsmLabelAttr {{0x[a-f0-9]+}} <col:6> Implicit "_Z3foos.carbon_thunk"
// CHECK:STDOUT: TranslationUnitDecl {{0x[a-f0-9]+}} <<invalid sloc>> <invalid sloc>
// --- import_thunk_required.carbon
@@ -88,3 +41,27 @@ import Cpp library "thunk_required.h";
fn F() {
Cpp.foo(1 as i16);
}
// --- return_thunk_required.h
auto foo() -> short;
// CHECK:STDOUT: |-FunctionDecl {{0x[a-f0-9]+}} <./return_thunk_required.h:[[@LINE-1]]:1, col:15> col:6 used foo 'auto () -> short'
// CHECK:STDOUT: `-FunctionDecl {{0x[a-f0-9]+}} <col:6> col:6 foo__carbon_thunk 'void (short * _Nonnull)' extern
// CHECK:STDOUT: |-ParmVarDecl {{0x[a-f0-9]+}} <col:6> col:6 used return 'short * _Nonnull':'short *'
// CHECK:STDOUT: |-CXXNewExpr {{0x[a-f0-9]+}} <col:6> 'short *' global Function {{0x[a-f0-9]+}} 'operator new' 'void *(__size_t, void *) noexcept'
// CHECK:STDOUT: | |-CallExpr {{0x[a-f0-9]+}} <col:6> 'short'
// CHECK:STDOUT: | | `-ImplicitCastExpr {{0x[a-f0-9]+}} <col:6> 'auto (*)() -> short' <FunctionToPointerDecay>
// CHECK:STDOUT: | | `-DeclRefExpr {{0x[a-f0-9]+}} <col:6> 'auto () -> short' Function {{0x[a-f0-9]+}} 'foo' 'auto () -> short'
// CHECK:STDOUT: | `-DeclRefExpr {{0x[a-f0-9]+}} <col:6> 'short * _Nonnull':'short *' lvalue ParmVar {{0x[a-f0-9]+}} 'return' 'short * _Nonnull':'short *'
// CHECK:STDOUT: |-AlwaysInlineAttr {{0x[a-f0-9]+}} <<invalid sloc>> Implicit always_inline
// CHECK:STDOUT: `-AsmLabelAttr {{0x[a-f0-9]+}} <col:6> Implicit "_Z3foov.carbon_thunk"
// --- import_return_thunk_required.carbon
library "[[@TEST_NAME]]";
import Cpp library "return_thunk_required.h";
fn F() -> i16 {
return Cpp.foo();
}
toolchain/check/testdata/interop/cpp/function/thunk_cpp26.carbon
Vendored
+28
View File
@@ -0,0 +1,28 @@
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
// INCLUDE-FILE: toolchain/testing/testdata/min_prelude/int.carbon
// EXTRA-ARGS: --clang-arg=--std=c++26
//
// AUTOUPDATE
// TIP: To test this file alone, run:
// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/check/testdata/interop/cpp/function/thunk_cpp26.carbon
// TIP: To dump output, run:
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/interop/cpp/function/thunk_cpp26.carbon
// --- thunk_required.h
auto foo(short a) -> short;
// --- import_thunk_required.carbon
library "[[@TEST_NAME]]";
import Cpp library "thunk_required.h";
fn F() {
// Placement operator new is `constexpr` in C++26. But that shouldn't cause
// problems for us because we declare our own operator new.
Cpp.foo(1 as i16);
}