We regard a function as 'unused' from the codegen perspective, so our warnings diverge from
gcc's unused warnings which don't get emitted if the function is referenced even in an unevaluated context
(e.g. in templates, sizeof, etc.). Also, saying that a function is 'unused' because it won't get codegen'ed
is somewhat misleading.
- Don't emit 'unused' warnings for functions that are referenced in any part of the user's code.
- A warning that an internal function/variable won't get emitted is useful though, so introduce
-Wunneeded-internal-declaration which will warn if a function/variable with internal linkage is not
"needed" ('used' from the codegen perspective), e.g:
static void foo() { }
template <int>
void bar() {
foo();
}
test.cpp:1:13: warning: function 'foo' is not needed and will not be emitted
static void foo() { }
^
Addresses rdar://8733476.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@129794 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/AST/DeclBase.h b/include/clang/AST/DeclBase.h
index 1656240..0473d1c 100644
--- a/include/clang/AST/DeclBase.h
+++ b/include/clang/AST/DeclBase.h
@@ -227,6 +227,12 @@
/// required.
unsigned Used : 1;
+ /// \brief Whether this declaration was "referenced".
+ /// The difference with 'Used' is whether the reference appears in a
+ /// evaluated context or not, e.g. functions used in uninstantiated templates
+ /// are regarded as "referenced" but not "used".
+ unsigned Referenced : 1;
+
protected:
/// Access - Used by C++ decls for the access specifier.
// NOTE: VC++ treats enums as signed, avoid using the AccessSpecifier enum
@@ -261,7 +267,7 @@
Decl(Kind DK, DeclContext *DC, SourceLocation L)
: NextDeclInContext(0), DeclCtx(DC),
Loc(L), DeclKind(DK), InvalidDecl(0),
- HasAttrs(false), Implicit(false), Used(false),
+ HasAttrs(false), Implicit(false), Used(false), Referenced(false),
Access(AS_none), PCHLevel(0), ChangedAfterLoad(false),
IdentifierNamespace(getIdentifierNamespaceForKind(DK)),
HasCachedLinkage(0)
@@ -271,7 +277,7 @@
Decl(Kind DK, EmptyShell Empty)
: NextDeclInContext(0), DeclKind(DK), InvalidDecl(0),
- HasAttrs(false), Implicit(false), Used(false),
+ HasAttrs(false), Implicit(false), Used(false), Referenced(false),
Access(AS_none), PCHLevel(0), ChangedAfterLoad(false),
IdentifierNamespace(getIdentifierNamespaceForKind(DK)),
HasCachedLinkage(0)
@@ -408,6 +414,11 @@
void setUsed(bool U = true) { Used = U; }
+ /// \brief Whether this declaration was referenced.
+ bool isReferenced() const;
+
+ void setReferenced(bool R = true) { Referenced = R; }
+
/// \brief Determine the availability of the given declaration.
///
/// This routine will determine the most restrictive availability of
diff --git a/include/clang/Basic/DiagnosticGroups.td b/include/clang/Basic/DiagnosticGroups.td
index c846550..15f3dbd 100644
--- a/include/clang/Basic/DiagnosticGroups.td
+++ b/include/clang/Basic/DiagnosticGroups.td
@@ -154,6 +154,8 @@
def UnusedParameter : DiagGroup<"unused-parameter">;
def UnusedValue : DiagGroup<"unused-value">;
def UnusedVariable : DiagGroup<"unused-variable">;
+def UnneededInternalDecl : DiagGroup<"unneeded-internal-declaration">;
+def UnneededMemberFunction : DiagGroup<"unneeded-member-function">;
def UsedButMarkedUnused : DiagGroup<"used-but-marked-unused">;
def ReadOnlySetterAttrs : DiagGroup<"readonly-setter-attrs">;
def Reorder : DiagGroup<"reorder">;
@@ -198,11 +200,16 @@
BoolConversions]>,
DiagCategory<"Value Conversion Issue">;
+def Unneeded : DiagGroup<"unneeded",
+ [UnneededInternalDecl
+ //,UnneededMemberFunction (clean-up llvm before enabling)
+ ]>;
+
def Unused : DiagGroup<"unused",
[UnusedArgument, UnusedFunction, UnusedLabel,
// UnusedParameter, (matches GCC's behavior)
// UnusedMemberFunction, (clean-up llvm before enabling)
- UnusedValue, UnusedVariable]>,
+ UnusedValue, UnusedVariable, Unneeded]>,
DiagCategory<"Unused Entity Issue">;
// Format settings.
diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 3ca45d4..ce592a3 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -116,6 +116,12 @@
InGroup<UnusedMemberFunction>, DefaultIgnore;
def warn_used_but_marked_unused: Warning<"%0 was marked unused but was used">,
InGroup<UsedButMarkedUnused>, DefaultIgnore;
+def warn_unneeded_internal_decl : Warning<
+ "%select{function|variable}0 %1 is not needed and will not be emitted">,
+ InGroup<UnneededInternalDecl>, DefaultIgnore;
+def warn_unneeded_member_function : Warning<
+ "member function %0 is not needed and will not be emitted">,
+ InGroup<UnneededMemberFunction>, DefaultIgnore;
def warn_parameter_size: Warning<
"%0 is a large (%1 bytes) pass-by-value argument; "
diff --git a/lib/AST/DeclBase.cpp b/lib/AST/DeclBase.cpp
index 673b718..41a0361 100644
--- a/lib/AST/DeclBase.cpp
+++ b/lib/AST/DeclBase.cpp
@@ -242,6 +242,18 @@
return false;
}
+bool Decl::isReferenced() const {
+ if (Referenced)
+ return true;
+
+ // Check redeclarations.
+ for (redecl_iterator I = redecls_begin(), E = redecls_end(); I != E; ++I)
+ if (I->Referenced)
+ return true;
+
+ return false;
+}
+
/// \brief Determine the availability of the given declaration based on
/// the target platform.
///
diff --git a/lib/Sema/Sema.cpp b/lib/Sema/Sema.cpp
index a83722d..403cf62 100644
--- a/lib/Sema/Sema.cpp
+++ b/lib/Sema/Sema.cpp
@@ -473,16 +473,30 @@
DiagD = FD;
if (DiagD->isDeleted())
continue; // Deleted functions are supposed to be unused.
- Diag(DiagD->getLocation(),
- isa<CXXMethodDecl>(DiagD) ? diag::warn_unused_member_function
- : diag::warn_unused_function)
- << DiagD->getDeclName();
+ if (DiagD->isReferenced()) {
+ if (isa<CXXMethodDecl>(DiagD))
+ Diag(DiagD->getLocation(), diag::warn_unneeded_member_function)
+ << DiagD->getDeclName();
+ else
+ Diag(DiagD->getLocation(), diag::warn_unneeded_internal_decl)
+ << /*function*/0 << DiagD->getDeclName();
+ } else {
+ Diag(DiagD->getLocation(),
+ isa<CXXMethodDecl>(DiagD) ? diag::warn_unused_member_function
+ : diag::warn_unused_function)
+ << DiagD->getDeclName();
+ }
} else {
const VarDecl *DiagD = cast<VarDecl>(*I)->getDefinition();
if (!DiagD)
DiagD = cast<VarDecl>(*I);
- Diag(DiagD->getLocation(), diag::warn_unused_variable)
- << DiagD->getDeclName();
+ if (DiagD->isReferenced()) {
+ Diag(DiagD->getLocation(), diag::warn_unneeded_internal_decl)
+ << /*variable*/1 << DiagD->getDeclName();
+ } else {
+ Diag(DiagD->getLocation(), diag::warn_unused_variable)
+ << DiagD->getDeclName();
+ }
}
}
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 9415673..8eb0177 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -9885,6 +9885,8 @@
void Sema::MarkDeclarationReferenced(SourceLocation Loc, Decl *D) {
assert(D && "No declaration?");
+ D->setReferenced();
+
if (D->isUsed(false))
return;
diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 3fe5fd5..0ff7ff4 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -298,8 +298,10 @@
Var->setAccess(D->getAccess());
- if (!D->isStaticDataMember())
+ if (!D->isStaticDataMember()) {
Var->setUsed(D->isUsed(false));
+ Var->setReferenced(D->isReferenced());
+ }
// FIXME: In theory, we could have a previous declaration for variables that
// are not static data members.
diff --git a/lib/Serialization/ASTReaderDecl.cpp b/lib/Serialization/ASTReaderDecl.cpp
index 5b4a64e..889ef73 100644
--- a/lib/Serialization/ASTReaderDecl.cpp
+++ b/lib/Serialization/ASTReaderDecl.cpp
@@ -214,6 +214,7 @@
}
D->setImplicit(Record[Idx++]);
D->setUsed(Record[Idx++]);
+ D->setReferenced(Record[Idx++]);
D->setAccess((AccessSpecifier)Record[Idx++]);
D->setPCHLevel(Record[Idx++] + (F.Type <= ASTReader::PCH));
}
diff --git a/lib/Serialization/ASTWriterDecl.cpp b/lib/Serialization/ASTWriterDecl.cpp
index 1306ffd..b3b55f5 100644
--- a/lib/Serialization/ASTWriterDecl.cpp
+++ b/lib/Serialization/ASTWriterDecl.cpp
@@ -141,6 +141,7 @@
Writer.WriteAttributes(D->getAttrs(), Record);
Record.push_back(D->isImplicit());
Record.push_back(D->isUsed(false));
+ Record.push_back(D->isReferenced());
Record.push_back(D->getAccess());
Record.push_back(D->getPCHLevel());
}
@@ -1133,6 +1134,7 @@
Abv->Add(BitCodeAbbrevOp(0)); // HasAttrs
Abv->Add(BitCodeAbbrevOp(0)); // isImplicit
Abv->Add(BitCodeAbbrevOp(0)); // isUsed
+ Abv->Add(BitCodeAbbrevOp(0)); // isReferenced
Abv->Add(BitCodeAbbrevOp(AS_none)); // C++ AccessSpecifier
Abv->Add(BitCodeAbbrevOp(0)); // PCH level
diff --git a/test/Sema/warn-unused-function.c b/test/Sema/warn-unused-function.c
index 5bbcf18..8f4cdcb 100644
--- a/test/Sema/warn-unused-function.c
+++ b/test/Sema/warn-unused-function.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -Wunused-function -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wunused-function -Wunneeded-internal-declaration -verify %s
// RUN: %clang_cc1 -fsyntax-only -verify -Wunused %s
// RUN: %clang_cc1 -fsyntax-only -verify -Wall %s
@@ -6,7 +6,7 @@
static void f2() {}
static void f1() {f2();} // expected-warning{{unused}}
-static int f0() { return 17; } // expected-warning{{unused}}
+static int f0() { return 17; } // expected-warning{{not needed and will not be emitted}}
int x = sizeof(f0());
static void f3();
@@ -46,7 +46,7 @@
static void f12(void);
// PR7923
-static void unused(void) { unused(); } // expected-warning{{unused}}
+static void unused(void) { unused(); } // expected-warning{{not needed and will not be emitted}}
// rdar://8728293
static void cleanupMalloc(char * const * const allocation) { }
diff --git a/test/SemaCXX/warn-unused-filescoped.cpp b/test/SemaCXX/warn-unused-filescoped.cpp
index c32acb0..dbff4b0 100644
--- a/test/SemaCXX/warn-unused-filescoped.cpp
+++ b/test/SemaCXX/warn-unused-filescoped.cpp
@@ -78,3 +78,12 @@
void test(A a); // expected-warning {{unused function}}
extern "C" void test4(A a);
}
+
+namespace rdar8733476 {
+ static void foo() { } // expected-warning {{not needed and will not be emitted}}
+
+ template <int>
+ void bar() {
+ foo();
+ }
+}