[clang] [SemaCXX] Make __builtin_addressof more like std::addressof (PR #78035)
Mital Ashok via cfe-commits
cfe-commits at lists.llvm.org
Sat Jan 13 06:02:50 PST 2024
https://github.com/MitalAshok created https://github.com/llvm/llvm-project/pull/78035
Fixes #77928
There are a few places which expect that, if for an expression `E->getType()->isBuiltinType(BuiltinType::Overload)`, then `E` must be an `OverloadExpr` or a `UnaryOperator` where `cast<UnaryOperator>(E)->getOpcode() == UO_AddrOf`.
Because `__builtin_addressof` is implemented similarly to `&`: https://github.com/llvm/llvm-project/blob/8d817f6479a5df874028a8b40fd30aecd3479005/clang/lib/Sema/SemaExpr.cpp#L15041 It can result in something with `OverloadTy` that isn't an `OverloadExpr` or a `UnaryOperator` (it's a `CallExpr`).
There are two things we can do to fix this: Either change those checks to accept both `&E` and `__builtin_addressof(E)`, or change it so `__builtin_addressof(E)` doesn't treat OverloadExprs differently.
This takes the latter approach, disabling `__builtin_addressof(name-of-overloaded-function)`.
It appears that GCC allows `__builtin_addressof(fn)` to be an overloaded function: <https://godbolt.org/z/G4xcbaffY>. The problem with allowing it in Clang is too much code generically deals with `CallExpr`s and you would have to special case `__builtin_addressof` to not try to resolve the arguments. And also it would be so rarely used in the first place (the fix being replacing `__builtin_addressof` with `&`)
>From 7384e99c5fc1bcba1a304735243e49e9738691aa Mon Sep 17 00:00:00 2001
From: Mital Ashok <mital at mitalashok.co.uk>
Date: Sat, 13 Jan 2024 10:48:21 +0000
Subject: [PATCH] [SemaCXX] Make __builtin_addressof more like std::addressof
Properly disable __builtin_addressof(f) where f is an overloaded function and __builtin_addressof(temporary).
__builtin_addressof(E) should now only work if E is bindable to an lvalue reference with the same type.
---
clang/include/clang/Sema/Sema.h | 3 ++-
clang/lib/Sema/SemaChecking.cpp | 2 +-
clang/lib/Sema/SemaExpr.cpp | 24 +++++++++++++++------
clang/test/SemaCXX/builtins.cpp | 38 ++++++++++++++++++++++++++++++++-
4 files changed, 57 insertions(+), 10 deletions(-)
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index cf2d4fbe6d3ba1..9941cbaadf780a 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -5805,7 +5805,8 @@ class Sema final {
const Expr *Op,
const CXXMethodDecl *MD);
- QualType CheckAddressOfOperand(ExprResult &Operand, SourceLocation OpLoc);
+ QualType CheckAddressOfOperand(ExprResult &Operand, SourceLocation OpLoc,
+ bool IsBuiltinAddressof = false);
bool CheckTypeTraitArity(unsigned Arity, SourceLocation Loc, size_t N);
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 74f8f626fb1637..e96436fd75bb68 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -242,7 +242,7 @@ static bool SemaBuiltinAddressof(Sema &S, CallExpr *TheCall) {
return true;
ExprResult Arg(TheCall->getArg(0));
- QualType ResultType = S.CheckAddressOfOperand(Arg, TheCall->getBeginLoc());
+ QualType ResultType = S.CheckAddressOfOperand(Arg, TheCall->getBeginLoc(), true);
if (ResultType.isNull())
return true;
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 2f48ea237cdfa4..518c51e77c7a99 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -15038,9 +15038,15 @@ bool Sema::CheckUseOfCXXMethodAsAddressOfOperand(SourceLocation OpLoc,
/// operator (C99 6.3.2.1p[2-4]), and its result is never an lvalue.
/// In C++, the operand might be an overloaded function name, in which case
/// we allow the '&' but retain the overloaded-function type.
-QualType Sema::CheckAddressOfOperand(ExprResult &OrigOp, SourceLocation OpLoc) {
+/// If IsBuiltinAddressof is true, this is spelt __builtin_addressof(E)
+/// instead of &E.
+QualType Sema::CheckAddressOfOperand(ExprResult &OrigOp, SourceLocation OpLoc,
+ bool IsBuiltinAddressof) {
if (const BuiltinType *PTy = OrigOp.get()->getType()->getAsPlaceholderType()){
if (PTy->getKind() == BuiltinType::Overload) {
+ if (IsBuiltinAddressof)
+ return QualType();
+
Expr *E = OrigOp.get()->IgnoreParens();
if (!isa<OverloadExpr>(E)) {
assert(cast<UnaryOperator>(E)->getOpcode() == UO_AddrOf);
@@ -15094,7 +15100,7 @@ QualType Sema::CheckAddressOfOperand(ExprResult &OrigOp, SourceLocation OpLoc) {
}
}
- if (getLangOpts().C99) {
+ if (!IsBuiltinAddressof && getLangOpts().C99) {
// Implement C99-only parts of addressof rules.
if (UnaryOperator* uOp = dyn_cast<UnaryOperator>(op)) {
if (uOp->getOpcode() == UO_Deref)
@@ -15116,11 +15122,11 @@ QualType Sema::CheckAddressOfOperand(ExprResult &OrigOp, SourceLocation OpLoc) {
unsigned AddressOfError = AO_No_Error;
if (lval == Expr::LV_ClassTemporary || lval == Expr::LV_ArrayTemporary) {
- bool sfinae = (bool)isSFINAEContext();
- Diag(OpLoc, isSFINAEContext() ? diag::err_typecheck_addrof_temporary
- : diag::ext_typecheck_addrof_temporary)
+ bool AllowTemporaryAddress = !isSFINAEContext() && !IsBuiltinAddressof;
+ Diag(OpLoc, AllowTemporaryAddress ? diag::ext_typecheck_addrof_temporary
+ : diag::err_typecheck_addrof_temporary)
<< op->getType() << op->getSourceRange();
- if (sfinae)
+ if (!AllowTemporaryAddress)
return QualType();
// Materialize the temporary as an lvalue so that we can take its address.
OrigOp = op =
@@ -15130,6 +15136,8 @@ QualType Sema::CheckAddressOfOperand(ExprResult &OrigOp, SourceLocation OpLoc) {
} else if (lval == Expr::LV_MemberFunction) {
// If it's an instance method, make a member pointer.
// The expression must have exactly the form &A::foo.
+ if (IsBuiltinAddressof)
+ return QualType();
// If the underlying expression isn't a decl ref, give up.
if (!isa<DeclRefExpr>(op)) {
@@ -15187,12 +15195,14 @@ QualType Sema::CheckAddressOfOperand(ExprResult &OrigOp, SourceLocation OpLoc) {
} else if (isa<MSPropertyDecl>(dcl)) {
AddressOfError = AO_Property_Expansion;
} else if (isa<FunctionTemplateDecl>(dcl)) {
- return Context.OverloadTy;
+ return IsBuiltinAddressof ? QualType() : Context.OverloadTy;
} else if (isa<FieldDecl>(dcl) || isa<IndirectFieldDecl>(dcl)) {
// Okay: we can take the address of a field.
// Could be a pointer to member, though, if there is an explicit
// scope qualifier for the class.
if (isa<DeclRefExpr>(op) && cast<DeclRefExpr>(op)->getQualifier()) {
+ if (IsBuiltinAddressof)
+ return QualType();
DeclContext *Ctx = dcl->getDeclContext();
if (Ctx && Ctx->isRecord()) {
if (dcl->getType()->isReferenceType()) {
diff --git a/clang/test/SemaCXX/builtins.cpp b/clang/test/SemaCXX/builtins.cpp
index 567094c94c171b..a59eb36eef4451 100644
--- a/clang/test/SemaCXX/builtins.cpp
+++ b/clang/test/SemaCXX/builtins.cpp
@@ -39,7 +39,43 @@ namespace addressof {
struct U { int n : 5; } u;
int *pbf = __builtin_addressof(u.n); // expected-error {{address of bit-field requested}}
- S *ptmp = __builtin_addressof(S{}); // expected-error {{taking the address of a temporary}} expected-warning {{temporary whose address is used as value of local variable 'ptmp' will be destroyed at the end of the full-expression}}
+ S *ptmp = __builtin_addressof(S{}); // expected-error {{taking the address of a temporary}}
+ int *memtmp = __builtin_addressof(T{}.n); // expected-error {{cannot take the address of an rvalue of type 'int'}}
+ S *pxval = __builtin_addressof(static_cast<S&&>(s)); // expected-error {{cannot take the address of an rvalue of type 'S'}}
+
+ void a(int) {} // expected-note 3 {{possible target for call}}
+ void a(float) {} // expected-note 3 {{possible target for call}}
+
+ int A = __builtin_addressof(a); // expected-error {{reference to overloaded function could not be resolved; did you mean to call it?}}
+ int B = &__builtin_addressof(a); // expected-error {{reference to overloaded function could not be resolved; did you mean to call it?}}
+ int C = __builtin_addressof(&a); // expected-error {{reference to overloaded function could not be resolved; did you mean to call it?}}
+
+ template<typename T>
+ constexpr decltype(void(__builtin_addressof(T::f)), true) can_take_address_of_f(int) { return true; }
+ template<typename T>
+ constexpr bool can_take_address_of_f(...) { return false; }
+
+ struct V1 { static void f(int); static void f(char); };
+ struct V2 { static void f(int); };
+ struct V3 { static int f; };
+ struct V4 {
+ int f;
+ int* g() {
+ return __builtin_addressof(f);
+ }
+ int* h() {
+ return __builtin_addressof(V4::f);
+ }
+ };
+ struct V5 { void f(int); };
+ struct V6 { using f = int; };
+
+ static_assert(!can_take_address_of_f<V1>(0), "");
+ static_assert( can_take_address_of_f<V2>(0), "");
+ static_assert( can_take_address_of_f<V3>(0), "");
+ static_assert(!can_take_address_of_f<V4>(0), "");
+ static_assert(!can_take_address_of_f<V5>(0), "");
+ static_assert(!can_take_address_of_f<V6>(0), "");
}
namespace function_start {
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