diff --git a/SConstruct b/SConstruct
index e1814c37c3..cc3af90d48 100755
--- a/SConstruct
+++ b/SConstruct
@@ -387,13 +387,7 @@ elif main['CLANG']:
     # parantheses are allowed due to Ruby's printing of the AST,
     # finally self assignments are allowed as the generated CPU code
     # is relying on this
-    main.Append(CCFLAGS=['-Wno-parentheses',
-                         '-Wno-self-assign',
-                         # Some versions of libstdc++ (4.8?) seem to
-                         # use struct hash and class hash
-                         # interchangeably.
-                         '-Wno-mismatched-tags',
-                         ])
+    main.Append(CCFLAGS=['-Wno-parentheses', '-Wno-self-assign'])
     conf.CheckCxxFlag('-Wno-c99-designator')
     conf.CheckCxxFlag('-Wno-defaulted-function-deleted')
 
diff --git a/src/arch/arm/pmu.hh b/src/arch/arm/pmu.hh
index 3cdcf1c0de..e8c63bfbc2 100644
--- a/src/arch/arm/pmu.hh
+++ b/src/arch/arm/pmu.hh
@@ -52,7 +52,7 @@
 #include "sim/sim_object.hh"
 #include "sim/system.hh"
 
-class ArmPMUParams;
+struct ArmPMUParams;
 class Platform;
 class ThreadContext;
 class ArmInterruptPin;
diff --git a/src/dev/arm/css/mhu.hh b/src/dev/arm/css/mhu.hh
index 17704e83f2..4e136055ad 100644
--- a/src/dev/arm/css/mhu.hh
+++ b/src/dev/arm/css/mhu.hh
@@ -41,12 +41,12 @@
 #include "dev/arm/doorbell.hh"
 #include "dev/io_device.hh"
 
-class Ap2ScpDoorbellParams;
+struct Ap2ScpDoorbellParams;
 class ArmInterruptPin;
 class MHU;
-class MHUParams;
+struct MHUParams;
 class Scp;
-class Scp2ApDoorbellParams;
+struct Scp2ApDoorbellParams;
 
 class MhuDoorbell : public Doorbell
 {
diff --git a/src/dev/arm/display.hh b/src/dev/arm/display.hh
index 1359487aa8..91819ffad2 100644
--- a/src/dev/arm/display.hh
+++ b/src/dev/arm/display.hh
@@ -40,7 +40,7 @@
 
 #include "sim/sim_object.hh"
 
-class DisplayParams;
+struct DisplayParams;
 
 class Display : public SimObject
 {
diff --git a/src/dev/arm/fvp_base_pwr_ctrl.hh b/src/dev/arm/fvp_base_pwr_ctrl.hh
index 4b1bc4cec9..948ad30347 100644
--- a/src/dev/arm/fvp_base_pwr_ctrl.hh
+++ b/src/dev/arm/fvp_base_pwr_ctrl.hh
@@ -44,7 +44,7 @@
 #include "dev/io_device.hh"
 
 class ArmSystem;
-class FVPBasePwrCtrlParams;
+struct FVPBasePwrCtrlParams;
 class ThreadContext;
 
 /**
diff --git a/src/dev/arm/generic_timer.hh b/src/dev/arm/generic_timer.hh
index 9a6663cd14..66048ccf7c 100644
--- a/src/dev/arm/generic_timer.hh
+++ b/src/dev/arm/generic_timer.hh
@@ -64,10 +64,10 @@
 ///     I2 - System Level Implementation of the Generic Timer
 
 class Checkpoint;
-class SystemCounterParams;
-class GenericTimerParams;
-class GenericTimerFrameParams;
-class GenericTimerMemParams;
+struct SystemCounterParams;
+struct GenericTimerParams;
+struct GenericTimerFrameParams;
+struct GenericTimerMemParams;
 
 /// Abstract class for elements whose events depend on the counting speed
 /// of the System Counter
diff --git a/src/dev/arm/gpu_nomali.hh b/src/dev/arm/gpu_nomali.hh
index a096edbee4..e30f3ed1f6 100644
--- a/src/dev/arm/gpu_nomali.hh
+++ b/src/dev/arm/gpu_nomali.hh
@@ -43,8 +43,8 @@
 #include "dev/io_device.hh"
 #include "libnomali/nomali.h"
 
-class NoMaliGpuParams;
-class CustomNoMaliGpuParams;
+struct NoMaliGpuParams;
+struct CustomNoMaliGpuParams;
 class RealView;
 
 class NoMaliGpu : public PioDevice
diff --git a/src/dev/arm/watchdog_generic.hh b/src/dev/arm/watchdog_generic.hh
index 24d3999280..177df936da 100644
--- a/src/dev/arm/watchdog_generic.hh
+++ b/src/dev/arm/watchdog_generic.hh
@@ -42,7 +42,7 @@
 #include "dev/io_device.hh"
 
 class ArmInterruptPin;
-class GenericWatchdogParams;
+struct GenericWatchdogParams;
 
 /**
  * @file
diff --git a/src/dev/arm/watchdog_sp805.hh b/src/dev/arm/watchdog_sp805.hh
index a64e4c9f61..5a6e962807 100644
--- a/src/dev/arm/watchdog_sp805.hh
+++ b/src/dev/arm/watchdog_sp805.hh
@@ -40,7 +40,7 @@
 
 #include "dev/arm/amba_device.hh"
 
-class Sp805Params;
+struct Sp805Params;
 
 /**
  * @file
diff --git a/src/gpu-compute/scheduler.hh b/src/gpu-compute/scheduler.hh
index 1acf643741..fbf72062b4 100644
--- a/src/gpu-compute/scheduler.hh
+++ b/src/gpu-compute/scheduler.hh
@@ -38,7 +38,7 @@
 
 #include "gpu-compute/scheduling_policy.hh"
 
-class ComputeUnitParams;
+struct ComputeUnitParams;
 
 class Scheduler
 {
diff --git a/src/mem/qos/mem_sink.hh b/src/mem/qos/mem_sink.hh
index 8a9708d898..27eded542d 100644
--- a/src/mem/qos/mem_sink.hh
+++ b/src/mem/qos/mem_sink.hh
@@ -46,7 +46,7 @@
 #include "mem/qport.hh"
 #include "params/QoSMemSinkCtrl.hh"
 
-class QoSMemSinkInterfaceParams;
+struct QoSMemSinkInterfaceParams;
 class QoSMemSinkInterface;
 
 namespace QoS {
diff --git a/src/mem/ruby/system/GPUCoalescer.hh b/src/mem/ruby/system/GPUCoalescer.hh
index 05d5269e9f..01ad1d2f1b 100644
--- a/src/mem/ruby/system/GPUCoalescer.hh
+++ b/src/mem/ruby/system/GPUCoalescer.hh
@@ -52,10 +52,10 @@
 
 class DataBlock;
 class CacheMsg;
-class MachineID;
+struct MachineID;
 class CacheMemory;
 
-class RubyGPUCoalescerParams;
+struct RubyGPUCoalescerParams;
 
 // List of packets that belongs to a specific instruction.
 typedef std::list<PacketPtr> PerInstPackets;
diff --git a/src/mem/ruby/system/VIPERCoalescer.hh b/src/mem/ruby/system/VIPERCoalescer.hh
index 213a67557d..40b32cc31c 100644
--- a/src/mem/ruby/system/VIPERCoalescer.hh
+++ b/src/mem/ruby/system/VIPERCoalescer.hh
@@ -46,10 +46,10 @@
 
 class DataBlock;
 class CacheMsg;
-class MachineID;
+struct MachineID;
 class CacheMemory;
 
-class VIPERCoalescerParams;
+struct VIPERCoalescerParams;
 
 class VIPERCoalescer : public GPUCoalescer
 {
diff --git a/src/sim/mem_state.hh b/src/sim/mem_state.hh
index c052389c3b..d0fa9bd2a6 100644
--- a/src/sim/mem_state.hh
+++ b/src/sim/mem_state.hh
@@ -42,7 +42,7 @@
 #include "sim/vma.hh"
 
 class Process;
-class ProcessParams;
+struct ProcessParams;
 class System;
 
 /**
diff --git a/src/sim/probe/probe.hh b/src/sim/probe/probe.hh
index 5becc26f27..eb0e445e93 100644
--- a/src/sim/probe/probe.hh
+++ b/src/sim/probe/probe.hh
@@ -69,7 +69,7 @@
 /** Forward declare the ProbeManager. */
 class ProbeManager;
 class ProbeListener;
-class ProbeListenerObjectParams;
+struct ProbeListenerObjectParams;
 
 /**
  * Name space containing shared probe point declarations.
diff --git a/src/sim/ticked_object.hh b/src/sim/ticked_object.hh
index 3991618081..abfa801dab 100644
--- a/src/sim/ticked_object.hh
+++ b/src/sim/ticked_object.hh
@@ -48,7 +48,7 @@
 
 #include "sim/clocked_object.hh"
 
-class TickedObjectParams;
+struct TickedObjectParams;
 
 /** Ticked attaches gem5's event queue/scheduler to evaluate
  *  calls and provides a start/stop interface to ticking.