Back out 6a7bfd84596e (bug 736501) because it broke the build on some versions of GCC (bug 754198)

configure.in

@@ -1757,15 +1757,11 @@ if test "$GNU_CC"; then
     # -Werror=return-type - catches missing returns, zero false positives
     # -Wtype-limits - catches overflow bugs, few false positives
     # -Wempty-body - catches bugs, e.g. "if (c); foo();", few false positives
-    # -Werror=unused-result - enforces __attribute__((warn_unused_result));
-    #     Seldom used in system headers, but frequently in Mozilla code to
-    #     enforce checking of fallible methods.
-
+    #
     _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wall -Wpointer-arith -Wdeclaration-after-statement"
     MOZ_C_SUPPORTS_WARNING(-W, error=return-type, ac_c_has_werror_return_type)
     MOZ_C_SUPPORTS_WARNING(-W, type-limits, ac_c_has_wtype_limits)
     MOZ_C_SUPPORTS_WARNING(-W, empty-body, ac_c_has_wempty_body)
-    MOZ_C_SUPPORTS_WARNING(-W, error=unused-result, ac_c_has_werror_unused_result)
     
     # Turn off the following warnings that -Wall/-pedantic turn on:
     # -Wno-unused - lots of violations in third-party code
@@ -1828,13 +1824,11 @@ if test "$GNU_CXX"; then
     # -Werror=return-type - catches missing returns, zero false positives
     # -Wtype-limits - catches overflow bugs, few false positives
     # -Wempty-body - catches bugs, e.g. "if (c); foo();", few false positives
-    # -Werror=unused-result - see above
-
+    #
     _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wall -Wpointer-arith -Woverloaded-virtual"
     MOZ_CXX_SUPPORTS_WARNING(-W, error=return-type, ac_cxx_has_werror_return_type)
     MOZ_CXX_SUPPORTS_WARNING(-W, type-limits, ac_cxx_has_wtype_limits)
     MOZ_CXX_SUPPORTS_WARNING(-W, empty-body, ac_cxx_has_wempty_body)
-    MOZ_CXX_SUPPORTS_WARNING(-W, error=unused-result, ac_cxx_has_werror_unused_result)
 
     # Turn off the following warnings that -Wall/-pedantic turn on:
     # -Wno-ctor-dtor-privacy - ???

dom/ipc/ContentParent.cpp

@@ -444,7 +444,7 @@ ContentParent::ContentParent()
         nsCString buildID(gAppData->buildID);
 
         //Sending all information to content process
-        unused << SendAppInfo(version, buildID);
+        SendAppInfo(version, buildID);
     }
 }
 
@@ -730,10 +730,10 @@ ContentParent::Observe(nsISupports* aSubject,
         unused << SendPMemoryReportRequestConstructor();
     }
     else if (!strcmp(aTopic, "child-gc-request")){
-        unused << SendGarbageCollect();
+        SendGarbageCollect();
     }
     else if (!strcmp(aTopic, "child-cc-request")){
-        unused << SendCycleCollect();
+        SendCycleCollect();
     }
     else if (!strcmp(aTopic, "last-pb-context-exited")) {
         unused << SendLastPrivateDocShellDestroyed();

dom/plugins/ipc/PluginInstanceParent.h

@@ -47,7 +47,6 @@
 #include "nsCoreAnimationSupport.h"
 #endif
 
-#include "mozilla/unused.h"
 #include "npfunctions.h"
 #include "nsAutoPtr.h"
 #include "nsDataHashtable.h"
@@ -306,7 +305,7 @@ public:
     nsresult HandleGUIEvent(const nsGUIEvent& anEvent, bool* handled);
 #endif
 
-    void DidComposite() { unused << SendNPP_DidComposite(); }
+    void DidComposite() { SendNPP_DidComposite(); }
 
 private:
     // Create an appropriate platform surface for a background of size

js/src/configure.in

@@ -1643,16 +1643,12 @@ if test "$GNU_CC"; then
     # -Werror=return-type - catches missing returns, zero false positives
     # -Wtype-limits - catches overflow bugs, few false positives
     # -Wempty-body - catches bugs, e.g. "if (c); foo();", few false positives
-    # -Werror=unused-result - enforces __attribute__((warn_unused_result));
-    #     Seldom used in system headers, but frequently in Mozilla code to
-    #     enforce checking of fallible methods.
-
+    #
     _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wall -Wpointer-arith -Wdeclaration-after-statement"
     MOZ_C_SUPPORTS_WARNING(-W, error=return-type, ac_c_has_werror_return_type)
     MOZ_C_SUPPORTS_WARNING(-W, type-limits, ac_c_has_wtype_limits)
     MOZ_C_SUPPORTS_WARNING(-W, empty-body, ac_c_has_wempty_body)
-    MOZ_C_SUPPORTS_WARNING(-W, error=unused-result, ac_c_has_werror_unused_result)
-
+    
     # Turn off the following warnings that -Wall/-pedantic turn on:
     # -Wno-unused - lots of violations in third-party code
     # -Wno-overlength-strings - we exceed the minimum maximum length frequently
@@ -1711,13 +1707,11 @@ if test "$GNU_CXX"; then
     # -Werror=return-type - catches missing returns, zero false positives
     # -Wtype-limits - catches overflow bugs, few false positives
     # -Wempty-body - catches bugs, e.g. "if (c); foo();", few false positives
-    # -Werror=unused-result - see above
-
+    #
     _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wall -Wpointer-arith -Woverloaded-virtual"
     MOZ_CXX_SUPPORTS_WARNING(-W, error=return-type, ac_cxx_has_werror_return_type)
     MOZ_CXX_SUPPORTS_WARNING(-W, type-limits, ac_cxx_has_wtype_limits)
     MOZ_CXX_SUPPORTS_WARNING(-W, empty-body, ac_cxx_has_wempty_body)
-    MOZ_CXX_SUPPORTS_WARNING(-W, error=unused-result, ac_cxx_has_werror_unused_result)
 
     # Turn off the following warnings that -Wall/-pedantic turn on:
     # -Wno-ctor-dtor-privacy - ???

toolkit/crashreporter/test/nsTestCrasher.cpp

@@ -3,9 +3,6 @@
 #include "nscore.h"
 #include "nsXULAppAPI.h"
 #include "nsExceptionHandler.h"
-#include "mozilla/unused.h"
-
-using mozilla::unused;
 
 /*
  * This pure virtual call example is from MSDN
@@ -66,9 +63,9 @@ void Crash(PRInt16 how)
     break;
   }
   case CRASH_OOM: {
-    unused << moz_xmalloc((size_t) -1);
-    unused << moz_xmalloc((size_t) -1);
-    unused << moz_xmalloc((size_t) -1);
+    (void) moz_xmalloc((size_t) -1);
+    (void) moz_xmalloc((size_t) -1);
+    (void) moz_xmalloc((size_t) -1);
     break;
   }
   default:

uriloader/prefetch/OfflineCacheUpdateParent.cpp

@@ -39,7 +39,6 @@
 #include "OfflineCacheUpdateParent.h"
 #include "nsOfflineCacheUpdate.h"
 #include "nsIApplicationCache.h"
-#include "mozilla/unused.h"
 
 #if defined(PR_LOGGING)
 //
@@ -143,7 +142,7 @@ OfflineCacheUpdateParent::UpdateStateChanged(nsIOfflineCacheUpdate *aUpdate, PRU
 
     LOG(("OfflineCacheUpdateParent::StateEvent [%p]", this));
 
-    unused << SendNotifyStateEvent(state);
+    SendNotifyStateEvent(state);
 
     if (state == nsIOfflineCacheUpdateObserver::STATE_FINISHED) {
         // Tell the child the particulars after the update has finished.
@@ -154,7 +153,7 @@ OfflineCacheUpdateParent::UpdateStateChanged(nsIOfflineCacheUpdate *aUpdate, PRU
         bool succeeded;
         aUpdate->GetSucceeded(&succeeded);
 
-        unused << SendFinish(succeeded, isUpgrade);
+        SendFinish(succeeded, isUpgrade);
     }
 
     return NS_OK;
@@ -173,7 +172,7 @@ OfflineCacheUpdateParent::ApplicationCacheAvailable(nsIApplicationCache *aApplic
     nsCString cacheGroupId;
     aApplicationCache->GetGroupID(cacheGroupId);
 
-    unused << SendAssociateDocuments(cacheGroupId, cacheClientId);
+    SendAssociateDocuments(cacheGroupId, cacheClientId);
     return NS_OK;
 }