Bug 1409598 - Change nsIXPCScriptable::className and nsIClassInfo::{contractID,classDescription} from string to AUTF8String. r=froydnj.

This lets us replace moz_xstrdup() of string literals with AssignLiteral(),
among other improvements.

--HG--
extra : rebase_source : 9994d8ccb4f196cf63564b0dac2ae6c4370defb4

caps/nsScriptSecurityManager.cpp

@@ -165,19 +165,17 @@ class ClassInfoData
 {
 public:
     ClassInfoData(nsIClassInfo *aClassInfo, const char *aName)
-        : mClassInfo(aClassInfo),
-          mFlags(0),
-          mName(const_cast<char *>(aName)),
-          mDidGetFlags(false),
-          mMustFreeName(false)
+      : mClassInfo(aClassInfo),
+        mFlags(0),
+        mName(aName),
+        mDidGetFlags(false)
     {
+      if (!aName) {
+        mName.SetIsVoid(true);
+      }
     }
 
-    ~ClassInfoData()
-    {
-        if (mMustFreeName)
-            free(mName);
-    }
+    ~ClassInfoData() = default;
 
     uint32_t GetFlags()
     {
@@ -202,29 +200,26 @@ public:
         return !!(GetFlags() & nsIClassInfo::DOM_OBJECT);
     }
 
-    const char* GetName()
+    void GetName(nsACString& aName)
     {
-        if (!mName) {
+        if (mName.IsVoid()) {
             if (mClassInfo) {
-                mClassInfo->GetClassDescription(&mName);
+                mClassInfo->GetClassDescription(mName);
             }
 
-            if (mName) {
-                mMustFreeName = true;
-            } else {
-                mName = const_cast<char *>("UnnamedClass");
+            if (mName.IsVoid()) {
+                mName.AssignLiteral("UnnamedClass");
             }
         }
 
-        return mName;
+        aName = mName;
     }
 
 private:
     nsIClassInfo *mClassInfo; // WEAK
     uint32_t mFlags;
-    char *mName;
+    nsCString mName;
     bool mDidGetFlags;
-    bool mMustFreeName;
 };
 
 /* static */
@@ -1315,22 +1310,24 @@ nsScriptSecurityManager::CanCreateWrapper(JSContext *cx,
     }
 
     //-- Access denied, report an error
-    nsAutoCString origin;
+    nsAutoCString originUTF8;
     nsIPrincipal* subjectPrincipal = nsContentUtils::SubjectPrincipal();
-    GetPrincipalDomainOrigin(subjectPrincipal, origin);
-    NS_ConvertUTF8toUTF16 originUnicode(origin);
-    NS_ConvertUTF8toUTF16 classInfoName(objClassInfo.GetName());
+    GetPrincipalDomainOrigin(subjectPrincipal, originUTF8);
+    NS_ConvertUTF8toUTF16 originUTF16(originUTF8);
+    nsAutoCString classInfoNameUTF8;
+    objClassInfo.GetName(classInfoNameUTF8);
+    NS_ConvertUTF8toUTF16 classInfoUTF16(classInfoNameUTF8);
     nsresult rv;
     nsAutoString errorMsg;
-    if (originUnicode.IsEmpty()) {
-        const char16_t* formatStrings[] = { classInfoName.get() };
+    if (originUTF16.IsEmpty()) {
+        const char16_t* formatStrings[] = { classInfoUTF16.get() };
         rv = sStrBundle->FormatStringFromName("CreateWrapperDenied",
                                               formatStrings,
                                               1,
                                               errorMsg);
     } else {
-        const char16_t* formatStrings[] = { classInfoName.get(),
-                                            originUnicode.get() };
+        const char16_t* formatStrings[] = { classInfoUTF16.get(),
+                                            originUTF16.get() };
         rv = sStrBundle->FormatStringFromName("CreateWrapperDeniedForOrigin",
                                               formatStrings,
                                               2,

dom/base/nsDOMClassInfo.cpp

@@ -562,15 +562,14 @@ nsDOMClassInfo::GetScriptableHelper(nsIXPCScriptable **_retval)
 }
 
 NS_IMETHODIMP
-nsDOMClassInfo::GetContractID(char **aContractID)
+nsDOMClassInfo::GetContractID(nsACString& aContractID)
 {
-  *aContractID = nullptr;
-
+  aContractID.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsDOMClassInfo::GetClassDescription(char **aClassDescription)
+nsDOMClassInfo::GetClassDescription(nsACString& aClassDescription)
 {
   return GetClassName(aClassDescription);
 }
@@ -599,10 +598,9 @@ nsDOMClassInfo::GetFlags(uint32_t *aFlags)
 // nsIXPCScriptable
 
 NS_IMETHODIMP
-nsDOMClassInfo::GetClassName(char **aClassName)
+nsDOMClassInfo::GetClassName(nsACString& aClassName)
 {
-  *aClassName = NS_strdup(mData->mClass.name);
-
+  aClassName.Assign(mData->mClass.name);
   return NS_OK;
 }
 

dom/file/nsHostObjectURI.cpp

@@ -244,18 +244,18 @@ nsHostObjectURI::GetScriptableHelper(nsIXPCScriptable **_retval)
 }
 
 NS_IMETHODIMP
-nsHostObjectURI::GetContractID(char * *aContractID)
+nsHostObjectURI::GetContractID(nsACString& aContractID)
 {
   // Make sure to modify any subclasses as needed if this ever
   // changes.
-  *aContractID = nullptr;
+  aContractID.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsHostObjectURI::GetClassDescription(char * *aClassDescription)
+nsHostObjectURI::GetClassDescription(nsACString& aClassDescription)
 {
-  *aClassDescription = nullptr;
+  aClassDescription.SetIsVoid(true);
   return NS_OK;
 }
 

js/xpconnect/idl/nsIXPCScriptable.idl

@@ -66,7 +66,7 @@ interface nsIXPConnectWrappedNative;
 [uuid(19b70b26-7c3f-437f-a04a-2a8f9e28b617)]
 interface nsIXPCScriptable : nsISupports
 {
-    readonly attribute string className;
+    readonly attribute AUTF8String className;
     [notxpcom,nostdcall] uint32_t getScriptableFlags();
     [notxpcom,nostdcall] jsClassPtr getClass();
     [notxpcom,nostdcall] JSClassPtr getJSClass();

js/xpconnect/public/xpc_map_end.h

@@ -23,9 +23,9 @@
 
 /**************************************************************/
 
-NS_IMETHODIMP XPC_MAP_CLASSNAME::GetClassName(char * *aClassName)
+NS_IMETHODIMP XPC_MAP_CLASSNAME::GetClassName(nsACString& aClassName)
 {
-    *aClassName = moz_xstrdup(XPC_MAP_QUOTED_CLASSNAME);
+    aClassName.AssignLiteral(XPC_MAP_QUOTED_CLASSNAME);
     return NS_OK;
 }
 

js/xpconnect/src/XPCComponents.cpp

@@ -140,16 +140,16 @@ nsXPCComponents_Interfaces::GetScriptableHelper(nsIXPCScriptable** retval)
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Interfaces::GetContractID(char * *aContractID)
+nsXPCComponents_Interfaces::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Interfaces::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_Interfaces::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_Interfaces");
+    aClassDescription.AssignLiteral("XPCComponents_Interfaces");
     return NS_OK;
 }
 
@@ -344,16 +344,17 @@ nsXPCComponents_InterfacesByID::GetScriptableHelper(nsIXPCScriptable** retval)
 }
 
 NS_IMETHODIMP
-nsXPCComponents_InterfacesByID::GetContractID(char * *aContractID)
+nsXPCComponents_InterfacesByID::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_InterfacesByID::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_InterfacesByID::GetClassDescription(
+    nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_InterfacesByID");
+    aClassDescription.AssignLiteral("XPCComponents_InterfacesByID");
     return NS_OK;
 }
 
@@ -550,16 +551,16 @@ nsXPCComponents_Classes::GetScriptableHelper(nsIXPCScriptable** retval)
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Classes::GetContractID(char * *aContractID)
+nsXPCComponents_Classes::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Classes::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_Classes::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_Classes");
+    aClassDescription.AssignLiteral("XPCComponents_Classes");
     return NS_OK;
 }
 
@@ -744,16 +745,16 @@ nsXPCComponents_ClassesByID::GetScriptableHelper(nsIXPCScriptable** retval)
 }
 
 NS_IMETHODIMP
-nsXPCComponents_ClassesByID::GetContractID(char * *aContractID)
+nsXPCComponents_ClassesByID::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_ClassesByID::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_ClassesByID::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_ClassesByID");
+    aClassDescription.AssignLiteral("XPCComponents_ClassesByID");
     return NS_OK;
 }
 
@@ -953,16 +954,16 @@ nsXPCComponents_Results::GetScriptableHelper(nsIXPCScriptable** retval)
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Results::GetContractID(char * *aContractID)
+nsXPCComponents_Results::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Results::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_Results::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_Results");
+    aClassDescription.AssignLiteral("XPCComponents_Results");
     return NS_OK;
 }
 
@@ -1122,16 +1123,16 @@ nsXPCComponents_ID::GetScriptableHelper(nsIXPCScriptable** retval)
 }
 
 NS_IMETHODIMP
-nsXPCComponents_ID::GetContractID(char * *aContractID)
+nsXPCComponents_ID::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_ID::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_ID::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_ID");
+    aClassDescription.AssignLiteral("XPCComponents_ID");
     return NS_OK;
 }
 
@@ -1298,16 +1299,16 @@ nsXPCComponents_Exception::GetScriptableHelper(nsIXPCScriptable** retval)
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Exception::GetContractID(char * *aContractID)
+nsXPCComponents_Exception::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Exception::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_Exception::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_Exception");
+    aClassDescription.AssignLiteral("XPCComponents_Exception");
     return NS_OK;
 }
 
@@ -1641,16 +1642,16 @@ nsXPCConstructor::GetScriptableHelper(nsIXPCScriptable** retval)
 }
 
 NS_IMETHODIMP
-nsXPCConstructor::GetContractID(char * *aContractID)
+nsXPCConstructor::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCConstructor::GetClassDescription(char * *aClassDescription)
+nsXPCConstructor::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCConstructor");
+    aClassDescription.AssignLiteral("XPCConstructor");
     return NS_OK;
 }
 
@@ -1842,16 +1843,16 @@ nsXPCComponents_Constructor::GetScriptableHelper(nsIXPCScriptable** retval)
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Constructor::GetContractID(char * *aContractID)
+nsXPCComponents_Constructor::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsXPCComponents_Constructor::GetClassDescription(char * *aClassDescription)
+nsXPCComponents_Constructor::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("XPCComponents_Constructor");
+    aClassDescription.AssignLiteral("XPCComponents_Constructor");
     return NS_OK;
 }
 

js/xpconnect/src/XPCRuntimeService.cpp

@@ -98,16 +98,16 @@ BackstagePass::GetScriptableHelper(nsIXPCScriptable** retval)
 }
 
 NS_IMETHODIMP
-BackstagePass::GetContractID(char * *aContractID)
+BackstagePass::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-BackstagePass::GetClassDescription(char * *aClassDescription)
+BackstagePass::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = moz_xstrdup("BackstagePass");
+    aClassDescription.AssignLiteral("BackstagePass");
     return NS_OK;
 }
 

modules/libjar/nsJARURI.cpp

@@ -172,16 +172,16 @@ nsJARURI::GetScriptableHelper(nsIXPCScriptable **_retval)
 }
 
 NS_IMETHODIMP
-nsJARURI::GetContractID(char * *aContractID)
+nsJARURI::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsJARURI::GetClassDescription(char * *aClassDescription)
+nsJARURI::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = nullptr;
+    aClassDescription.SetIsVoid(true);
     return NS_OK;
 }
 

netwerk/base/RustURL.cpp

@@ -681,16 +681,16 @@ RustURL::GetScriptableHelper(nsIXPCScriptable * *_retval)
 }
 
 NS_IMETHODIMP
-RustURL::GetContractID(char * *aContractID)
+RustURL::GetContractID(nsACString& aContractID)
 {
-  *aContractID = nullptr;
+  aContractID.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-RustURL::GetClassDescription(char * *aClassDescription)
+RustURL::GetClassDescription(nsACString& aClassDescription)
 {
-  *aClassDescription = nullptr;
+  aClassDescription.SetIsVoid(true);
   return NS_OK;
 }
 

netwerk/base/nsSimpleURI.cpp

@@ -744,18 +744,18 @@ nsSimpleURI::GetScriptableHelper(nsIXPCScriptable **_retval)
 }
 
 NS_IMETHODIMP
-nsSimpleURI::GetContractID(char * *aContractID)
+nsSimpleURI::GetContractID(nsACString& aContractID)
 {
     // Make sure to modify any subclasses as needed if this ever
     // changes.
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsSimpleURI::GetClassDescription(char * *aClassDescription)
+nsSimpleURI::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = nullptr;
+    aClassDescription.SetIsVoid(true);
     return NS_OK;
 }
 

netwerk/base/nsSocketTransport2.cpp

@@ -2971,16 +2971,16 @@ nsSocketTransport::GetScriptableHelper(nsIXPCScriptable **_retval)
 }
 
 NS_IMETHODIMP
-nsSocketTransport::GetContractID(char * *aContractID)
+nsSocketTransport::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsSocketTransport::GetClassDescription(char * *aClassDescription)
+nsSocketTransport::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = nullptr;
+    aClassDescription.SetIsVoid(true);
     return NS_OK;
 }
 

netwerk/base/nsStandardURL.cpp

@@ -3838,16 +3838,16 @@ nsStandardURL::GetScriptableHelper(nsIXPCScriptable **_retval)
 }
 
 NS_IMETHODIMP
-nsStandardURL::GetContractID(char * *aContractID)
+nsStandardURL::GetContractID(nsACString& aContractID)
 {
-    *aContractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsStandardURL::GetClassDescription(char * *aClassDescription)
+nsStandardURL::GetClassDescription(nsACString& aClassDescription)
 {
-    *aClassDescription = nullptr;
+    aClassDescription.SetIsVoid(true);
     return NS_OK;
 }
 

security/manager/ssl/TransportSecurityInfo.cpp

@@ -432,16 +432,16 @@ TransportSecurityInfo::GetScriptableHelper(nsIXPCScriptable **_retval)
 }
 
 NS_IMETHODIMP
-TransportSecurityInfo::GetContractID(char * *aContractID)
+TransportSecurityInfo::GetContractID(nsACString& aContractID)
 {
-  *aContractID = nullptr;
+  aContractID.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-TransportSecurityInfo::GetClassDescription(char * *aClassDescription)
+TransportSecurityInfo::GetClassDescription(nsACString& aClassDescription)
 {
-  *aClassDescription = nullptr;
+  aClassDescription.SetIsVoid(true);
   return NS_OK;
 }
 

security/manager/ssl/nsNSSCertificate.cpp

@@ -1538,16 +1538,16 @@ nsNSSCertificate::GetScriptableHelper(nsIXPCScriptable** _retval)
 }
 
 NS_IMETHODIMP
-nsNSSCertificate::GetContractID(char** aContractID)
+nsNSSCertificate::GetContractID(nsACString& aContractID)
 {
-  *aContractID = nullptr;
+  aContractID.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsNSSCertificate::GetClassDescription(char** aClassDescription)
+nsNSSCertificate::GetClassDescription(nsACString& aClassDescription)
 {
-  *aClassDescription = nullptr;
+  aClassDescription.SetIsVoid(true);
   return NS_OK;
 }
 

security/manager/ssl/nsSSLStatus.cpp

@@ -294,16 +294,16 @@ nsSSLStatus::GetScriptableHelper(nsIXPCScriptable** aHelper)
 }
 
 NS_IMETHODIMP
-nsSSLStatus::GetContractID(char** aContractID)
+nsSSLStatus::GetContractID(nsACString& aContractID)
 {
-  *aContractID = nullptr;
+  aContractID.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsSSLStatus::GetClassDescription(char** aClassDescription)
+nsSSLStatus::GetClassDescription(nsACString& aClassDescription)
 {
-  *aClassDescription = nullptr;
+  aClassDescription.SetIsVoid(true);
   return NS_OK;
 }
 

storage/mozStorageAsyncStatement.cpp

@@ -63,16 +63,16 @@ public:
   }
 
   NS_IMETHOD
-  GetContractID(char **_contractID) override
+  GetContractID(nsACString& aContractID) override
   {
-    *_contractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_OK;
   }
 
   NS_IMETHOD
-  GetClassDescription(char **_desc) override
+  GetClassDescription(nsACString& aDesc) override
   {
-    *_desc = nullptr;
+    aDesc.SetIsVoid(true);
     return NS_OK;
   }
 

storage/mozStorageStatement.cpp

@@ -66,16 +66,16 @@ public:
   }
 
   NS_IMETHOD
-  GetContractID(char **_contractID) override
+  GetContractID(nsACString& aContractID) override
   {
-    *_contractID = nullptr;
+    aContractID.SetIsVoid(true);
     return NS_OK;
   }
 
   NS_IMETHOD
-  GetClassDescription(char **_desc) override
+  GetClassDescription(nsACString& aDesc) override
   {
-    *_desc = nullptr;
+    aDesc.SetIsVoid(true);
     return NS_OK;
   }
 

xpcom/base/nsClassInfoImpl.cpp

@@ -36,17 +36,17 @@ GenericClassInfo::GetScriptableHelper(nsIXPCScriptable** aHelper)
 }
 
 NS_IMETHODIMP
-GenericClassInfo::GetContractID(char** aContractID)
+GenericClassInfo::GetContractID(nsACString& aContractID)
 {
   NS_ERROR("GetContractID not implemented");
-  *aContractID = nullptr;
+  aContractID.SetIsVoid(true);
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP
-GenericClassInfo::GetClassDescription(char** aDescription)
+GenericClassInfo::GetClassDescription(nsACString& aDescription)
 {
-  *aDescription = nullptr;
+  aDescription.SetIsVoid(true);
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 

xpcom/base/nsISupportsImpl.h

@@ -1206,16 +1206,16 @@ _class::GetScriptableHelper(nsIXPCScriptable** _retval)                       \
 }                                                                             \
                                                                               \
 NS_IMETHODIMP                                                                 \
-_class::GetContractID(char** _contractID)                                     \
+_class::GetContractID(nsACString& _contractID)                                \
 {                                                                             \
-  *_contractID = nullptr;                                                     \
+  _contractID.SetIsVoid(true);                                                \
   return NS_OK;                                                               \
 }                                                                             \
                                                                               \
 NS_IMETHODIMP                                                                 \
-_class::GetClassDescription(char** _classDescription)                         \
+_class::GetClassDescription(nsACString& _classDescription)                    \
 {                                                                             \
-  *_classDescription = nullptr;                                               \
+  _classDescription.SetIsVoid(true);                                          \
   return NS_OK;                                                               \
 }                                                                             \
                                                                               \

xpcom/components/nsIClassInfo.idl

@@ -36,14 +36,14 @@ interface nsIClassInfo : nsISupports
 
     /**
      * A contract ID through which an instance of this class can be created
-     * (or accessed as a service, if |flags & SINGLETON|), or null.
+     * (or accessed as a service, if |flags & SINGLETON|), or null/void.
      */
-    readonly attribute string   contractID;
+    readonly attribute AUTF8String contractID;
 
     /**
-     * A human readable string naming the class, or null.
+     * A human readable string naming the class, or null/void.
      */
-    readonly attribute string   classDescription;
+    readonly attribute AUTF8String classDescription;
 
     /**
      * A class ID through which an instance of this class can be created

xpcom/threads/nsThread.cpp

@@ -143,16 +143,16 @@ nsThreadClassInfo::GetScriptableHelper(nsIXPCScriptable** aResult)
 }
 
 NS_IMETHODIMP
-nsThreadClassInfo::GetContractID(char** aResult)
+nsThreadClassInfo::GetContractID(nsACString& aResult)
 {
-  *aResult = nullptr;
+  aResult.SetIsVoid(true);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsThreadClassInfo::GetClassDescription(char** aResult)
+nsThreadClassInfo::GetClassDescription(nsACString& aResult)
 {
-  *aResult = nullptr;
+  aResult.SetIsVoid(true);
   return NS_OK;
 }