Add a command line option 'fregister_global_dtors_with_atexit' to
register destructor functions annotated with __attribute__((destructor))
using __cxa_atexit or atexit.
Register destructor functions annotated with __attribute__((destructor))
calling __cxa_atexit in a synthesized constructor function instead of
emitting references to the functions in a special section.
The primary reason for adding this option is that we are planning to
deprecate the __mod_term_funcs section on Darwin in the future. This
feature is enabled by default only on Darwin. Users who do not want this
can use command line option 'fno_register_global_dtors_with_atexit' to
disable it.
rdar://problem/33887655
Differential Revision: https://reviews.llvm.org/D45578
llvm-svn: 330199
diff --git a/clang/lib/CodeGen/CGDeclCXX.cpp b/clang/lib/CodeGen/CGDeclCXX.cpp
index e47a65e..5e237d7 100644
--- a/clang/lib/CodeGen/CGDeclCXX.cpp
+++ b/clang/lib/CodeGen/CGDeclCXX.cpp
@@ -236,7 +236,10 @@
llvm::Constant *addr) {
// Create a function which calls the destructor.
llvm::Constant *dtorStub = createAtExitStub(VD, dtor, addr);
+ registerGlobalDtorWithAtExit(dtorStub);
+}
+void CodeGenFunction::registerGlobalDtorWithAtExit(llvm::Constant *dtorStub) {
// extern "C" int atexit(void (*f)(void));
llvm::FunctionType *atexitTy =
llvm::FunctionType::get(IntTy, dtorStub->getType(), false);
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 27b0677..84118a5 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -3696,6 +3696,9 @@
void registerGlobalDtorWithAtExit(const VarDecl &D, llvm::Constant *fn,
llvm::Constant *addr);
+ /// Call atexit() with function dtorStub.
+ void registerGlobalDtorWithAtExit(llvm::Constant *dtorStub);
+
/// Emit code in this function to perform a guarded variable
/// initialization. Guarded initializations are used when it's not
/// possible to prove that an initialization will be done exactly
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 42a8cd8..a21527a 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -397,6 +397,7 @@
emitMultiVersionFunctions();
EmitCXXGlobalInitFunc();
EmitCXXGlobalDtorFunc();
+ registerGlobalDtorsWithAtExit();
EmitCXXThreadLocalInitFunc();
if (ObjCRuntime)
if (llvm::Function *ObjCInitFunction = ObjCRuntime->ModuleInitFunction())
@@ -1026,6 +1027,11 @@
/// AddGlobalDtor - Add a function to the list that will be called
/// when the module is unloaded.
void CodeGenModule::AddGlobalDtor(llvm::Function *Dtor, int Priority) {
+ if (CodeGenOpts.RegisterGlobalDtorsWithAtExit) {
+ DtorsUsingAtExit[Priority].push_back(Dtor);
+ return;
+ }
+
// FIXME: Type coercion of void()* types.
GlobalDtors.push_back(Structor(Priority, Dtor, nullptr));
}
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index 5daa4e9..76af56b 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -1336,6 +1336,12 @@
void checkAliases();
+ std::map<int, llvm::TinyPtrVector<llvm::Function *>> DtorsUsingAtExit;
+
+ /// Register functions annotated with __attribute__((destructor)) using
+ /// __cxa_atexit, if it is available, or atexit otherwise.
+ void registerGlobalDtorsWithAtExit();
+
void emitMultiVersionFunctions();
/// Emit any vtables which we deferred and still have a use for.
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index 68274ea..f92d7ec 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -34,6 +34,7 @@
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Value.h"
+#include "llvm/Support/ScopedPrinter.h"
using namespace clang;
using namespace CodeGen;
@@ -2195,6 +2196,13 @@
auto *GV = cast<llvm::GlobalValue>(handle->stripPointerCasts());
GV->setVisibility(llvm::GlobalValue::HiddenVisibility);
+ if (!addr)
+ // addr is null when we are trying to register a dtor annotated with
+ // __attribute__((destructor)) in a constructor function. Using null here is
+ // okay because this argument is just passed back to the destructor
+ // function.
+ addr = llvm::Constant::getNullValue(CGF.Int8PtrTy);
+
llvm::Value *args[] = {
llvm::ConstantExpr::getBitCast(dtor, dtorTy),
llvm::ConstantExpr::getBitCast(addr, CGF.Int8PtrTy),
@@ -2203,6 +2211,48 @@
CGF.EmitNounwindRuntimeCall(atexit, args);
}
+void CodeGenModule::registerGlobalDtorsWithAtExit() {
+ for (const auto I : DtorsUsingAtExit) {
+ int Priority = I.first;
+ const llvm::TinyPtrVector<llvm::Function *> &Dtors = I.second;
+
+ // Create a function that registers destructors that have the same priority.
+ //
+ // Since constructor functions are run in non-descending order of their
+ // priorities, destructors are registered in non-descending order of their
+ // priorities, and since destructor functions are run in the reverse order
+ // of their registration, destructor functions are run in non-ascending
+ // order of their priorities.
+ CodeGenFunction CGF(*this);
+ std::string GlobalInitFnName =
+ std::string("__GLOBAL_init_") + llvm::to_string(Priority);
+ llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
+ llvm::Function *GlobalInitFn = CreateGlobalInitOrDestructFunction(
+ FTy, GlobalInitFnName, getTypes().arrangeNullaryFunction(),
+ SourceLocation());
+ ASTContext &Ctx = getContext();
+ FunctionDecl *FD = FunctionDecl::Create(
+ Ctx, Ctx.getTranslationUnitDecl(), SourceLocation(), SourceLocation(),
+ &Ctx.Idents.get(GlobalInitFnName), Ctx.VoidTy, nullptr, SC_Static,
+ false, false);
+ CGF.StartFunction(GlobalDecl(FD), getContext().VoidTy, GlobalInitFn,
+ getTypes().arrangeNullaryFunction(), FunctionArgList(),
+ SourceLocation(), SourceLocation());
+
+ for (auto *Dtor : Dtors) {
+ // Register the destructor function calling __cxa_atexit if it is
+ // available. Otherwise fall back on calling atexit.
+ if (getCodeGenOpts().CXAAtExit)
+ emitGlobalDtorWithCXAAtExit(CGF, Dtor, nullptr, false);
+ else
+ CGF.registerGlobalDtorWithAtExit(Dtor);
+ }
+
+ CGF.FinishFunction();
+ AddGlobalCtor(GlobalInitFn, Priority, nullptr);
+ }
+}
+
/// Register a global destructor as best as we know how.
void ItaniumCXXABI::registerGlobalDtor(CodeGenFunction &CGF,
const VarDecl &D,