r211766 - Sema: Allow dllimport entities in template args for mingw

[David Majnemer]

Author: majnemer
Date: Thu Jun 26 02:48:46 2014
New Revision: 211766

URL: http://llvm.org/viewvc/llvm-project?rev=211766&view=rev
Log:
Sema: Allow dllimport entities in template args for mingw

Previously dllimport variables inside of template arguments relied on
not using the C++11 codepath when -fms-compatibility was set.

While this allowed us to achieve compatibility with MSVC, it did so at
the expense of MingW.

Instead, try to use the DeclRefExpr we dig out of the template argument.
If it has the dllimport attribute, accept it and skip the C++11
null-pointer check.

Modified:
    cfe/trunk/lib/Sema/SemaTemplate.cpp
    cfe/trunk/test/SemaCXX/PR19955.cpp

Modified: cfe/trunk/lib/Sema/SemaTemplate.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaTemplate.cpp?rev=211766&r1=211765&r2=211766&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaTemplate.cpp (original)
+++ cfe/trunk/lib/Sema/SemaTemplate.cpp Thu Jun 26 02:48:46 2014
@@ -4337,22 +4337,6 @@ CheckTemplateArgumentAddressOfObjectOrFu
   Expr *Arg = ArgIn;
   QualType ArgType = Arg->getType();
 
-  // If our parameter has pointer type, check for a null template value.
-  if (ParamType->isPointerType() || ParamType->isNullPtrType()) {
-    switch (isNullPointerValueTemplateArgument(S, Param, ParamType, Arg)) {
-    case NPV_NullPointer:
-      S.Diag(Arg->getExprLoc(), diag::warn_cxx98_compat_template_arg_null);
-      Converted = TemplateArgument(ParamType, /*isNullPtr*/true);
-      return false;
-
-    case NPV_Error:
-      return true;
-        
-    case NPV_NotNullPointer:
-      break;
-    }
-  }
-
   bool AddressTaken = false;
   SourceLocation AddrOpLoc;
   if (S.getLangOpts().MicrosoftExt) {
@@ -4440,6 +4424,32 @@ CheckTemplateArgumentAddressOfObjectOrFu
       Arg = subst->getReplacement()->IgnoreImpCasts();
   }
 
+  DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Arg);
+  ValueDecl *Entity = DRE ? DRE->getDecl() : nullptr;
+
+  // If our parameter has pointer type, check for a null template value.
+  if (ParamType->isPointerType() || ParamType->isNullPtrType()) {
+    NullPointerValueKind NPV;
+    // dllimport'd entities aren't constant but are available inside of template
+    // arguments.
+    if (Entity && Entity->hasAttr<DLLImportAttr>())
+      NPV = NPV_NotNullPointer;
+    else
+      NPV = isNullPointerValueTemplateArgument(S, Param, ParamType, ArgIn);
+    switch (NPV) {
+    case NPV_NullPointer:
+      S.Diag(Arg->getExprLoc(), diag::warn_cxx98_compat_template_arg_null);
+      Converted = TemplateArgument(ParamType, /*isNullPtr=*/true);
+      return false;
+
+    case NPV_Error:
+      return true;
+
+    case NPV_NotNullPointer:
+      break;
+    }
+  }
+
   // Stop checking the precise nature of the argument if it is value dependent,
   // it should be checked when instantiated.
   if (Arg->isValueDependent()) {
@@ -4456,7 +4466,6 @@ CheckTemplateArgumentAddressOfObjectOrFu
     return false;
   }
 
-  DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Arg);
   if (!DRE) {
     S.Diag(Arg->getLocStart(), diag::err_template_arg_not_decl_ref)
     << Arg->getSourceRange();
@@ -4464,8 +4473,6 @@ CheckTemplateArgumentAddressOfObjectOrFu
     return true;
   }
 
-  ValueDecl *Entity = DRE->getDecl();
-
   // Cannot refer to non-static data members
   if (isa<FieldDecl>(Entity) || isa<IndirectFieldDecl>(Entity)) {
     S.Diag(Arg->getLocStart(), diag::err_template_arg_field)

Modified: cfe/trunk/test/SemaCXX/PR19955.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/PR19955.cpp?rev=211766&r1=211765&r2=211766&view=diff
==============================================================================
--- cfe/trunk/test/SemaCXX/PR19955.cpp (original)
+++ cfe/trunk/test/SemaCXX/PR19955.cpp Thu Jun 26 02:48:46 2014
@@ -1,4 +1,5 @@
-// RUN: %clang_cc1 -triple i686-win32 -fms-compatibility -verify -std=c++11 %s
+// RUN: %clang_cc1 -triple i686-win32 -verify -std=c++11 %s
+// RUN: %clang_cc1 -triple i686-mingw32 -verify -std=c++11 %s
 
 extern int __attribute__((dllimport)) var;
 constexpr int *varp = &var; // expected-error {{must be initialized by a constant expression}}