From e23f731ef773c79fe4cbd1c994a1f12eff661259 Mon Sep 17 00:00:00 2001
From: timoore <timoore>
Date: Wed, 15 Aug 2007 15:22:44 +0000
Subject: [PATCH] Fix for weather interpolation problem from Anders Gidenstam
 Anders said: With Stuart's help I've looked closer at this and I think I've
 tracked down the cause of the problem: At least on my computer the sort()
 call on line 234 in Environment/environment_ctrl.cxx sorts the vector entries
 by memory address instead of altitude, i.e. the custom comparison predicate
 is not used. This causes the tables of environment conditions to be reordered
 into a wrong order at some weather updates, depending, basically, on where
 the memory allocator places the objects. (Btw. why are they are freshly
 allocated for each update?)

---
 src/Environment/environment_ctrl.cxx | 7 ++++++-
 src/Environment/environment_ctrl.hxx | 2 ++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/Environment/environment_ctrl.cxx b/src/Environment/environment_ctrl.cxx
index aa777d288..82af0e027 100644
--- a/src/Environment/environment_ctrl.cxx
+++ b/src/Environment/environment_ctrl.cxx
@@ -231,7 +231,7 @@ FGInterpolateEnvironmentCtrl::read_table (const SGPropertyNode * node,
             table.push_back(b);
         }
     }
-    sort(table.begin(), table.end());
+    sort(table.begin(), table.end(), bucket::lessThan);
 }
 
 void
@@ -312,6 +312,11 @@ FGInterpolateEnvironmentCtrl::bucket::operator< (const bucket &b) const
     return (altitude_ft < b.altitude_ft);
 }
 
+bool
+FGInterpolateEnvironmentCtrl::bucket::lessThan(bucket *a, bucket *b)
+{
+    return (a->altitude_ft) < (b->altitude_ft);
+}
 
 
 ////////////////////////////////////////////////////////////////////////
diff --git a/src/Environment/environment_ctrl.hxx b/src/Environment/environment_ctrl.hxx
index d82de9da1..69b2bdf22 100644
--- a/src/Environment/environment_ctrl.hxx
+++ b/src/Environment/environment_ctrl.hxx
@@ -134,6 +134,8 @@ private:
         double altitude_ft;
         FGEnvironment environment;
         bool operator< (const bucket &b) const;
+        // LessThan predicate for bucket pointers.
+        static bool lessThan(bucket *a, bucket *b);
     };
 
     void read_table (const SGPropertyNode * node, vector<bucket *> &table);
-- 
2.39.5