From: David Majnemer <david.majnemer@gmail.com>
Date: Tue, 24 Jun 2014 06:40:51 +0000 (+0000)
Subject: AST: Address of dllimport functions isn't constant
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=3e93571576d89e49dd1dc830d40243eb3a350790;p=clang

AST: Address of dllimport functions isn't constant

The address of dllimport functions can be accessed one of two ways:
- Through the IAT which is symbolically referred to with a symbol
  starting with __imp_.
- Via the wrapper-function which ends up calling through the __imp_
  symbol.

The problem with using the wrapper-function is that it's address will
not compare as equal in all translation units.  Specifically, it will
compare unequally with the translation unit which defines the function.

This fixes PR19955.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@211570 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index d25ecd043d..c57a802512 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -4373,8 +4373,11 @@ static bool EvaluateLValue(const Expr *E, LValue &Result, EvalInfo &Info) {
 }
 
 bool LValueExprEvaluator::VisitDeclRefExpr(const DeclRefExpr *E) {
-  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(E->getDecl()))
+  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(E->getDecl())) {
+    if (FD->hasAttr<DLLImportAttr>())
+      return ZeroInitialization(E);
     return Success(FD);
+  }
   if (const VarDecl *VD = dyn_cast<VarDecl>(E->getDecl()))
     return VisitVarDecl(E, VD);
   return Error(E);
diff --git a/test/CodeGenCXX/PR19955.cpp b/test/CodeGenCXX/PR19955.cpp
index 7d54ac3899..9e101550b4 100644
--- a/test/CodeGenCXX/PR19955.cpp
+++ b/test/CodeGenCXX/PR19955.cpp
@@ -1,10 +1,27 @@
 // RUN: %clang_cc1 -triple i686-windows-msvc -fno-rtti -emit-llvm -std=c++1y -O0 -o - %s | FileCheck %s
-// RUN: %clang_cc1 -triple x86_64-windows-msvc -fno-rtti -emit-llvm -std=c++1y -O0 -o - %s | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-windows-msvc -fno-rtti -emit-llvm -std=c++1y -O0 -o - %s | FileCheck %s --check-prefix X64
 
-extern int __declspec(dllimport) x;
-extern long long y;
-// CHECK-DAG: @"\01?y@@3_JA" = global i64 0
-long long y = (long long)&x;
+extern int __declspec(dllimport) var;
+extern void __declspec(dllimport) fun();
 
-// CHECK-LABEL: @"\01??__Ey@@YAXXZ"
-// CHECK-DAG: @"\01?y@@3_JA"
+extern int *varp;
+int *varp = &var;
+// CHECK-DAG: @"\01?varp@@3PAHA" = global i32* null
+// X64-DAG: @"\01?varp@@3PEAHEA" = global i32* null
+
+extern void (*funp)();
+void (*funp)() = &fun;
+// CHECK-DAG: @"\01?funp@@3P6AXXZA" = global void ()* null
+// X64-DAG: @"\01?funp@@3P6AXXZEA" = global void ()* null
+
+// CHECK-LABEL: @"\01??__Evarp@@YAXXZ"
+// CHECK-DAG: store i32* @"\01?var@@3HA", i32** @"\01?varp@@3PAHA"
+
+// X64-LABEL: @"\01??__Evarp@@YAXXZ"
+// X64-DAG: store i32* @"\01?var@@3HA", i32** @"\01?varp@@3PEAHEA"
+
+// CHECK-LABEL: @"\01??__Efunp@@YAXXZ"()
+// CHECK-DAG: store void ()* @"\01?fun@@YAXXZ", void ()** @"\01?funp@@3P6AXXZA"
+
+// X64-LABEL: @"\01??__Efunp@@YAXXZ"()
+// X64-DAG: store void ()* @"\01?fun@@YAXXZ", void ()** @"\01?funp@@3P6AXXZEA"
diff --git a/test/SemaCXX/PR19955.cpp b/test/SemaCXX/PR19955.cpp
index 81fa70d7f5..e0d4618f2c 100644
--- a/test/SemaCXX/PR19955.cpp
+++ b/test/SemaCXX/PR19955.cpp
@@ -1,4 +1,7 @@
 // RUN: %clang_cc1 -triple i686-win32 -verify -std=c++11 %s
 
-extern int __attribute__((dllimport)) y;
-constexpr int *x = &y; // expected-error {{must be initialized by a constant expression}}
+extern int __attribute__((dllimport)) var;
+constexpr int *varp = &var; // expected-error {{must be initialized by a constant expression}}
+
+extern __attribute__((dllimport)) void fun();
+constexpr void (*funp)(void) = &fun; // expected-error {{must be initialized by a constant expression}}