MEM: Make port proxies use references rather than pointers

This patch is adding a clearer design intent to all objects that would
not be complete without a port proxy by making the proxies members
rathen than dynamically allocated. In essence, if NULL would not be a
valid value for the proxy, then we avoid using a pointer to make this
clear.

The same approach is used for the methods using these proxies, such as
loadSections, that now use references rather than pointers to better
reflect the fact that NULL would not be an acceptable value (in fact
the code would break and that is how this patch started out).

Overall the concept of "using a reference to express unconditional
composition where a NULL pointer is never valid" could be done on a
much broader scale throughout the code base, but for now it is only
done in the locations affected by the proxies.

1 files changed, 9 insertions, 10 deletions

diff --git a/src/cpu/thread_state.cc b/src/cpu/thread_state.cc
index 33c0d719c..3d58b4da4 100644
--- a/src/cpu/thread_state.cc
+++ b/src/cpu/thread_state.cc
@@ -106,6 +106,9 @@ ThreadState::initMemProxies(ThreadContext *tc)
     // (i.e. due to restoring from a checkpoint and later switching
     // in.
     if (physProxy == NULL)
+        // this cannot be done in the constructor as the thread state
+        // itself is created in the base cpu constructor and the
+        // getPort is a virtual function at the moment
         physProxy = new PortProxy(baseCpu->getDataPort());
     if (virtProxy == NULL)
         virtProxy = new FSTranslatingPortProxy(tc);
@@ -125,16 +128,12 @@ ThreadState::profileSample()
         profile->sample(profileNode, profilePC);
 }
 
-SETranslatingPortProxy *
+SETranslatingPortProxy &
 ThreadState::getMemProxy()
 {
-    if (proxy != NULL)
-        return proxy;
-
-    /* Use this port proxy to for syscall emulation writes to memory. */
-    proxy = new SETranslatingPortProxy(*process->system->getSystemPort(),
-                                       process,
-                                       SETranslatingPortProxy::NextPage);
-
-    return proxy;
+    if (proxy == NULL)
+        proxy = new SETranslatingPortProxy(baseCpu->getDataPort(),
+                                           process,
+                                           SETranslatingPortProxy::NextPage);
+    return *proxy;
 }