Implement explicit hook priority in vmethod interpose.

This resolves a getName order conflict between power-meter and rename.

library/VTableInterpose.cpp

@@ -247,8 +247,9 @@ void VMethodInterposeLinkBase::set_chain(void *chain)
     addr_to_method_pointer_(chain_mptr, chain);
 }
 
-VMethodInterposeLinkBase::VMethodInterposeLinkBase(virtual_identity *host, int vmethod_idx, void *interpose_method, void *chain_mptr)
-    : host(host), vmethod_idx(vmethod_idx), interpose_method(interpose_method), chain_mptr(chain_mptr),
+VMethodInterposeLinkBase::VMethodInterposeLinkBase(virtual_identity *host, int vmethod_idx, void *interpose_method, void *chain_mptr, int priority)
+    : host(host), vmethod_idx(vmethod_idx), interpose_method(interpose_method),
+      chain_mptr(chain_mptr), priority(priority),
       applied(false), saved_chain(NULL), next(NULL), prev(NULL)
 {
     if (vmethod_idx < 0 || interpose_method == NULL)
@@ -349,15 +350,26 @@ bool VMethodInterposeLinkBase::apply(bool enable)
         return false;
 
     // Retrieve the current vtable entry
-    void *old_ptr = host->get_vmethod_ptr(vmethod_idx);
     VMethodInterposeLinkBase *old_link = host->interpose_list[vmethod_idx];
+    VMethodInterposeLinkBase *next_link = NULL;
 
+    while (old_link && old_link->host == host && old_link->priority > priority)
+    {
+        next_link = old_link;
+        old_link = old_link->prev;
+    }
+
+    void *old_ptr = next_link ? next_link->saved_chain : host->get_vmethod_ptr(vmethod_idx);
     assert(old_ptr != NULL && (!old_link || old_link->interpose_method == old_ptr));
 
     // Apply the new method ptr
     set_chain(old_ptr);
 
-    if (!host->set_vmethod_ptr(vmethod_idx, interpose_method))
+    if (next_link)
+    {
+        next_link->set_chain(interpose_method);
+    }
+    else if (!host->set_vmethod_ptr(vmethod_idx, interpose_method))
     {
         set_chain(NULL);
         return false;
@@ -365,8 +377,13 @@ bool VMethodInterposeLinkBase::apply(bool enable)
 
     // Push the current link into the home host
     applied = true;
-    host->interpose_list[vmethod_idx] = this;
     prev = old_link;
+    next = next_link;
+
+    if (next_link)
+        next_link->prev = this;
+    else
+        host->interpose_list[vmethod_idx] = this;
 
     child_hosts.clear();
     child_next.clear();
@@ -374,13 +391,22 @@ bool VMethodInterposeLinkBase::apply(bool enable)
     if (old_link && old_link->host == host)
     {
         // If the old link is home, just push into the plain chain
-        assert(old_link->next == NULL);
+        assert(old_link->next == next_link);
         old_link->next = this;
 
         // Child links belong to the topmost local entry
         child_hosts.swap(old_link->child_hosts);
         child_next.swap(old_link->child_next);
     }
+    else if (next_link)
+    {
+        if (old_link)
+        {
+            assert(old_link->child_next.count(next_link));
+            old_link->child_next.erase(next_link);
+            old_link->child_next.insert(this);
+        }
+    }
     else
     {
         // If creating a new local chain, find children with same vmethod
@@ -401,6 +427,8 @@ bool VMethodInterposeLinkBase::apply(bool enable)
         }
     }
 
+    assert (!next_link || (child_next.empty() && child_hosts.empty()));
+
     // Chain subclass hooks
     for (auto it = child_next.begin(); it != child_next.end(); ++it)
     {

library/include/VTableInterpose.h

@@ -87,7 +87,8 @@ namespace DFHack
        with code defined by DFHack, while retaining ability to
        call the original code. The API can be safely used from
        plugins, and multiple hooks for the same vmethod are
-       automatically chained in undefined order.
+       automatically chained (subclass before superclass; at same
+       level highest priority called first; undefined order otherwise).
 
        Usage:
 
@@ -105,6 +106,8 @@ namespace DFHack
        };
 
        IMPLEMENT_VMETHOD_INTERPOSE(my_hack, foo);
+       or
+       IMPLEMENT_VMETHOD_INTERPOSE_PRIO(my_hack, foo, priority);
 
        void init() {
            if (!INTERPOSE_HOOK(my_hack, foo).apply())
@@ -121,9 +124,11 @@ namespace DFHack
     static DFHack::VMethodInterposeLink<interpose_base,interpose_ptr_##name> interpose_##name; \
     rtype interpose_fn_##name args
 
-#define IMPLEMENT_VMETHOD_INTERPOSE(class,name) \
+#define IMPLEMENT_VMETHOD_INTERPOSE_PRIO(class,name,priority) \
     DFHack::VMethodInterposeLink<class::interpose_base,class::interpose_ptr_##name> \
-        class::interpose_##name(&class::interpose_base::name, &class::interpose_fn_##name);
+        class::interpose_##name(&class::interpose_base::name, &class::interpose_fn_##name, priority);
+
+#define IMPLEMENT_VMETHOD_INTERPOSE(class,name) IMPLEMENT_VMETHOD_INTERPOSE_PRIO(class,name,0)
 
 #define INTERPOSE_NEXT(name) (this->*interpose_##name.chain)
 #define INTERPOSE_HOOK(class, name) (class::interpose_##name)
@@ -140,6 +145,7 @@ namespace DFHack
         int vmethod_idx;
         void *interpose_method; // Pointer to the code of the interposing method
         void *chain_mptr;       // Pointer to the chain field below
+        int priority;
 
         bool applied;
         void *saved_chain;      // Previous pointer to the code
@@ -155,7 +161,7 @@ namespace DFHack
         VMethodInterposeLinkBase *get_first_interpose(virtual_identity *id);
         void find_child_hosts(virtual_identity *cur, void *vmptr);
     public:
-        VMethodInterposeLinkBase(virtual_identity *host, int vmethod_idx, void *interpose_method, void *chain_mptr);
+        VMethodInterposeLinkBase(virtual_identity *host, int vmethod_idx, void *interpose_method, void *chain_mptr, int priority);
         ~VMethodInterposeLinkBase();
 
         bool is_applied() { return applied; }
@@ -171,12 +177,13 @@ namespace DFHack
         operator Ptr () { return chain; }
 
         template<class Ptr2>
-        VMethodInterposeLink(Ptr target, Ptr2 src)
+        VMethodInterposeLink(Ptr target, Ptr2 src, int priority)
             : VMethodInterposeLinkBase(
                 &Base::_identity,
                 vmethod_pointer_to_idx(target),
                 method_pointer_to_addr(src),
-                &chain
+                &chain,
+                priority
               )
         { src = target; /* check compatibility */ }
     };

plugins/rename.cpp

@@ -130,7 +130,7 @@ DFhackCExport command_result plugin_shutdown ( color_ostream &out )
                 INTERPOSE_NEXT(getName)(buf); \
         } \
     }; \
-    IMPLEMENT_VMETHOD_INTERPOSE(cname##_hook, getName);
+    IMPLEMENT_VMETHOD_INTERPOSE_PRIO(cname##_hook, getName, 100);
 KNOWN_BUILDINGS
 #undef BUILDING