[Clang] Support a user-defined __dso_handle

This fixes PR49198: Wrong usage of __dso_handle in user code leads to
a compiler crash.

When Init is an address of the global itself, we need to track it
across RAUW. Otherwise the initializer can be destroyed if the global
is replaced.

Differential Revision: https://reviews.llvm.org/D101156

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 9b31ecd..1f23ce7 100644 (file)
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -4284,7 +4284,7 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D,
       OpenMPRuntime->emitTargetGlobalVariable(D))
     return;
 
-  llvm::Constant *Init = nullptr;
+  llvm::TrackingVH<llvm::Constant> Init;
   bool NeedsGlobalCtor = false;
   bool NeedsGlobalDtor =
       D->needsDestruction(getContext()) == QualType::DK_cxx_destructor;
@@ -4330,9 +4330,8 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D,
   } else {
     initializedGlobalDecl = GlobalDecl(D);
     emitter.emplace(*this);
-    Init = emitter->tryEmitForInitializer(*InitDecl);
-
-    if (!Init) {
+    llvm::Constant *Initializer = emitter->tryEmitForInitializer(*InitDecl);
+    if (!Initializer) {
       QualType T = InitExpr->getType();
       if (D->getType()->isReferenceType())
         T = D->getType();
@@ -4345,6 +4344,7 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D,
         Init = llvm::UndefValue::get(getTypes().ConvertType(T));
       }
     } else {
+      Init = Initializer;
       // We don't need an initializer, so remove the entry for the delayed
       // initializer position (just in case this entry was delayed) if we
       // also don't need to register a destructor.

diff --git a/clang/test/CodeGenCXX/dso-handle-custom.cpp b/clang/test/CodeGenCXX/dso-handle-custom.cpp
new file mode 100644 (file)
index 0000000..a6bc34f
--- /dev/null
+++ b/clang/test/CodeGenCXX/dso-handle-custom.cpp
@@ -0,0 +1,23 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-llvm -fexceptions %s -o - | FileCheck %s --check-prefixes CHECK,CHECK-DEFAULT
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-llvm -fexceptions %s -o - -DHIDDEN | FileCheck %s --check-prefixes CHECK,CHECK-HIDDEN
+
+class A {
+public:
+  ~A();
+} a;
+
+// CHECK-DEFAULT: @__dso_handle = global i8* bitcast (i8** @__dso_handle to i8*), align 8
+// CHECK-HIDDEN: @__dso_handle = hidden global i8* bitcast (i8** @__dso_handle to i8*), align 8
+// CHECK: define internal void @__cxx_global_var_init()
+// CHECK:   call i32 @__cxa_atexit({{.*}}, {{.*}}, i8* bitcast (i8** @__dso_handle to i8*))
+
+#ifdef HIDDEN
+void *__dso_handle __attribute__((__visibility__("hidden"))) = &__dso_handle;
+#else
+void *__dso_handle = &__dso_handle;
+#endif
+
+void use(void *);
+void use_dso_handle() {
+  use(__dso_handle);
+}