sim,systemc: Use slightly non-standard constructors for custom create()

Rather than rely on the default create() method being a weak symbol, we
can just not have a compliant constructor signature which means we need
to (and therefore can) define our own custom create().

Change-Id: I6009d72db0c103b5724d1ba7e20c0bd4a2b761e5
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/42588
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Earl Ou <shunhsingou@google.com>

src/sim/root.cc

@@ -166,7 +166,7 @@ Root::timeSyncSpinThreshold(Time newThreshold)
     timeSyncEnable(en);
 }
 
-Root::Root(const RootParams &p)
+Root::Root(const RootParams &p, int)
     : SimObject(p), _enabled(false), _periodTick(p.time_sync_period),
       syncEvent([this]{ timeSync(); }, name())
 {
@@ -216,5 +216,5 @@ RootParams::create() const
     FullSystem = full_system;
     FullSystemInt = full_system ? 1 : 0;
 
-    return new Root(*this);
+    return new Root(*this, 0);
 }

src/sim/root.hh

@@ -134,7 +134,9 @@ class Root : public SimObject
 
     PARAMS(Root);
 
-    Root(const Params &p);
+    // The int parameter is ignored, it's just so we can define a custom
+    // create() method.
+    Root(const Params &p, int);
 
     /** Schedule the timesync event at startup().
      */

src/systemc/core/kernel.cc

@@ -54,7 +54,7 @@ bool Kernel::endOfSimulationComplete() { return endComplete; }
 sc_core::sc_status Kernel::status() { return _status; }
 void Kernel::status(sc_core::sc_status s) { _status = s; }
 
-Kernel::Kernel(const Params &params) :
+Kernel::Kernel(const Params &params, int) :
     SimObject(params), t0Event(this, false, EventBase::Default_Pri - 1)
 {
     // Install ourselves as the scheduler's event manager.
@@ -187,6 +187,6 @@ SystemC_KernelParams::create() const
 {
     panic_if(sc_gem5::kernel,
             "Only one systemc kernel object may be defined.\n");
-    sc_gem5::kernel = new sc_gem5::Kernel(*this);
+    sc_gem5::kernel = new sc_gem5::Kernel(*this, 0);
     return sc_gem5::kernel;
 }

src/systemc/core/kernel.hh

@@ -46,7 +46,7 @@ class Kernel : public SimObject
 {
   public:
     typedef SystemC_KernelParams Params;
-    Kernel(const Params &params);
+    Kernel(const Params &params, int);
 
     void init() override;
     void regStats() override;