misc: Appease GCC 8

GCC 8 adds a number of new warnings to -Wall which generate errors.

- Fix memset to 0 for structs by adding casts.
- Fix cast with const when the const was ignored.
- Fix catch a polymorphic type by value

We now compile with GCC 8!

Change-Id: Iab70ce11190eee67608fc25c0bedff170152b153
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/11949
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>

src/arch/x86/decoder.hh

@@ -239,7 +239,7 @@ class Decoder
         outOfBytes(true), instDone(false),
         state(ResetState)
     {
-        memset(&emi, 0, sizeof(emi));
+        emi.reset();
         mode = LongMode;
         submode = SixtyFourBitMode;
         emi.mode.mode = mode;

src/arch/x86/types.hh

@@ -199,6 +199,10 @@ namespace X86ISA
     //The intermediate structure used by the x86 decoder.
     struct ExtMachInst
     {
+        void reset() {
+            memset(static_cast<void *>(this), 0, sizeof(*this));
+        }
+
         //Prefixes
         LegacyPrefixVector legacy;
         Rex rex;

src/base/bitunion.hh

@@ -435,7 +435,7 @@ namespace BitfieldBackend
     inline std::ostream &
     bitfieldBackendPrinter(std::ostream &os, const char &t)
     {
-        os << (const int)t;
+        os << (int)t;
         return os;
     }
 
@@ -443,7 +443,7 @@ namespace BitfieldBackend
     inline std::ostream &
     bitfieldBackendPrinter(std::ostream &os, const unsigned char &t)
     {
-        os << (const unsigned int)t;
+        os << (unsigned int)t;
         return os;
     }
 }

src/cpu/testers/traffic_gen/pygen.cc

@@ -74,7 +74,7 @@ PyTrafficGen::nextGenerator()
             metaGenerator->cast<std::shared_ptr<BaseGen>>();
         metaGenerator++;
         return gen;
-    } catch (py::cast_error) {
+    } catch (py::cast_error&) {
         fatal("Meta generator didn't return a valid trace generator\n");
     }
 }

src/dev/storage/ide_ctrl.cc

@@ -83,7 +83,7 @@ IdeController::Channel::Channel(
     cmdAddr(0), cmdSize(_cmdSize), ctrlAddr(0), ctrlSize(_ctrlSize),
     master(NULL), slave(NULL), selected(NULL)
 {
-    memset(&bmiRegs, 0, sizeof(bmiRegs));
+    bmiRegs.reset();
     bmiRegs.status.dmaCap0 = 1;
     bmiRegs.status.dmaCap1 = 1;
 }

src/dev/storage/ide_ctrl.hh

@@ -81,6 +81,10 @@ class IdeController : public PciDevice
         /** Registers used for bus master interface */
         struct BMIRegs
         {
+            void reset() {
+                memset(static_cast<void *>(this), 0, sizeof(*this));
+            }
+
             BMICommandReg command;
             uint8_t reserved0;
             BMIStatusReg status;