[clang] [Sema] Mark alias/ifunc targets used and consider mangled names (PR #87130)
Fangrui Song via cfe-commits
cfe-commits at lists.llvm.org
Thu Apr 4 15:52:47 PDT 2024
https://github.com/MaskRay updated https://github.com/llvm/llvm-project/pull/87130
>From 23422a0b3af3e070fed5ae86ed0f67acec066c0a Mon Sep 17 00:00:00 2001
From: Fangrui Song <i at maskray.me>
Date: Fri, 29 Mar 2024 17:48:14 -0700
Subject: [PATCH 1/2] =?UTF-8?q?[=F0=9D=98=80=F0=9D=97=BD=F0=9D=97=BF]=20in?=
=?UTF-8?q?itial=20version?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Created using spr 1.3.5-bogner
---
clang/lib/Sema/CMakeLists.txt | 1 +
clang/lib/Sema/SemaDeclAttr.cpp | 31 +++++++++++++++++----------
clang/test/AST/ast-dump-attr-json.cpp | 1 +
clang/test/Sema/alias-unused.c | 30 +++++++++++++++++++++++++-
4 files changed, 51 insertions(+), 12 deletions(-)
diff --git a/clang/lib/Sema/CMakeLists.txt b/clang/lib/Sema/CMakeLists.txt
index e8bff07ced0cfa..7657536fabd1eb 100644
--- a/clang/lib/Sema/CMakeLists.txt
+++ b/clang/lib/Sema/CMakeLists.txt
@@ -1,5 +1,6 @@
set(LLVM_LINK_COMPONENTS
Core
+ Demangle
FrontendHLSL
FrontendOpenMP
MC
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index f25f3afd0f4af2..8ed5242f325e5e 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -42,6 +42,7 @@
#include "clang/Sema/SemaInternal.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringExtras.h"
+#include "llvm/Demangle/Demangle.h"
#include "llvm/IR/Assumptions.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/Support/Error.h"
@@ -1980,6 +1981,23 @@ static void handleWeakRefAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
D->addAttr(::new (S.Context) WeakRefAttr(S.Context, AL));
}
+// Mark alias/ifunc target as used. For C++, we look up the demangled name
+// ignoring parameters. This should handle the majority of use cases while
+// leaveing false positives for namespace scope names and false negatives in
+// the presence of overloads.
+static void markUsedForAliasOrIfunc(Sema &S, Decl *D, const ParsedAttr &AL,
+ StringRef Str) {
+ char *Demangled = llvm::itaniumDemangle(Str, /*ParseParams=*/false);
+ if (Demangled)
+ Str = Demangled;
+ const DeclarationNameInfo target(&S.Context.Idents.get(Str), AL.getLoc());
+ LookupResult LR(S, target, Sema::LookupOrdinaryName);
+ if (S.LookupQualifiedName(LR, S.getCurLexicalContext()))
+ for (NamedDecl *ND : LR)
+ ND->markUsed(S.Context);
+ free(Demangled);
+}
+
static void handleIFuncAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
StringRef Str;
if (!S.checkStringLiteralArgumentAttr(AL, 0, Str))
@@ -1992,6 +2010,7 @@ static void handleIFuncAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
return;
}
+ markUsedForAliasOrIfunc(S, D, AL, Str);
D->addAttr(::new (S.Context) IFuncAttr(S.Context, AL, Str));
}
@@ -2026,17 +2045,7 @@ static void handleAliasAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
}
}
- // Mark target used to prevent unneeded-internal-declaration warnings.
- if (!S.LangOpts.CPlusPlus) {
- // FIXME: demangle Str for C++, as the attribute refers to the mangled
- // linkage name, not the pre-mangled identifier.
- const DeclarationNameInfo target(&S.Context.Idents.get(Str), AL.getLoc());
- LookupResult LR(S, target, Sema::LookupOrdinaryName);
- if (S.LookupQualifiedName(LR, S.getCurLexicalContext()))
- for (NamedDecl *ND : LR)
- ND->markUsed(S.Context);
- }
-
+ markUsedForAliasOrIfunc(S, D, AL, Str);
D->addAttr(::new (S.Context) AliasAttr(S.Context, AL, Str));
}
diff --git a/clang/test/AST/ast-dump-attr-json.cpp b/clang/test/AST/ast-dump-attr-json.cpp
index 051c2956abfdf7..883e584bfedf07 100644
--- a/clang/test/AST/ast-dump-attr-json.cpp
+++ b/clang/test/AST/ast-dump-attr-json.cpp
@@ -46,6 +46,7 @@ __thread __attribute__ ((tls_model ("local-exec"))) int tls_model_var;
// CHECK-NEXT: "tokLen": 11
// CHECK-NEXT: }
// CHECK-NEXT: },
+// CHECK-NEXT: "isUsed": true,
// CHECK-NEXT: "name": "global_decl",
// CHECK-NEXT: "mangledName": "global_decl",
// CHECK-NEXT: "type": {
diff --git a/clang/test/Sema/alias-unused.c b/clang/test/Sema/alias-unused.c
index de9fc8cc737662..030b5737a93a21 100644
--- a/clang/test/Sema/alias-unused.c
+++ b/clang/test/Sema/alias-unused.c
@@ -1,7 +1,35 @@
-// RUN: %clang_cc1 -triple x86_64-linux-gnu -Wunneeded-internal-declaration -x c -verify %s
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -Wunused -x c -verify %s
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -Wunused -x c++ -verify %s
+
+#ifdef __cplusplus
+extern "C" {
+#else
// expected-no-diagnostics
+#endif
static int f(void) { return 42; }
int g(void) __attribute__((alias("f")));
static int foo [] = { 42, 0xDEAD };
extern typeof(foo) bar __attribute__((unused, alias("foo")));
+
+static int (*resolver(void))(void) { return f; }
+int ifunc(void) __attribute__((ifunc("resolver")));
+
+#ifdef __cplusplus
+}
+
+/// We demangle alias/ifunc target and mark all found functions as used.
+static int f1(int) { return 42; }
+static int f1(void) { return 42; }
+int g1(void) __attribute__((alias("_ZL2f1v")));
+
+static int (*resolver1(void))(void) { return f; }
+static int (*resolver1(int))(void) { return f; }
+int ifunc1(void) __attribute__((ifunc("_ZL9resolver1v")));
+
+namespace ns {
+static int f2(int) { return 42; } // expected-warning{{unused function 'f2'}}
+static int f2(void) { return 42; } // expected-warning{{unused function 'f2'}}
+int g2(void) __attribute__((alias("_ZN2nsL2f2Ev")));
+}
+#endif
>From 6f2a3daed983eac8acd5988799f678124b06fb35 Mon Sep 17 00:00:00 2001
From: Fangrui Song <i at maskray.me>
Date: Thu, 4 Apr 2024 15:52:37 -0700
Subject: [PATCH 2/2] code style
Created using spr 1.3.5-bogner
---
clang/lib/Sema/SemaDeclAttr.cpp | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 6a29634cdb089e..eb34445dc147f6 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -1989,13 +1989,12 @@ static void markUsedForAliasOrIfunc(Sema &S, Decl *D, const ParsedAttr &AL,
char *Demangled = nullptr;
if (S.getASTContext().getCXXABIKind() != TargetCXXABI::Microsoft)
Demangled = llvm::itaniumDemangle(Str, /*ParseParams=*/false);
- std::unique_ptr<MangleContext> MC;
- MC.reset(S.getASTContext().createMangleContext());
+ std::unique_ptr<MangleContext> MC(S.Context.createMangleContext());
SmallString<256> Name;
- const DeclarationNameInfo target(
+ const DeclarationNameInfo Target(
&S.Context.Idents.get(Demangled ? Demangled : Str), AL.getLoc());
- LookupResult LR(S, target, Sema::LookupOrdinaryName);
+ LookupResult LR(S, Target, Sema::LookupOrdinaryName);
if (S.LookupName(LR, S.TUScope)) {
for (NamedDecl *ND : LR) {
if (MC->shouldMangleDeclName(ND)) {
More information about the cfe-commits
mailing list