[Csp-commits] svn:csp r1869 - trunk/csp/csplib/data

[<sv...@ww...>]

Author: mkrose
Date: 2006-04-02 00:04:49 -0800 (Sun, 02 Apr 2006)
New Revision: 1869

Modified:
   trunk/csp/csplib/data/LUT.cpp
   trunk/csp/csplib/data/LUT.h
Log:
Fix memory corruption in LUT code under GCC 3.4/4.0 related to
const reference initialization from temporary objects.  Both
the bug and the fix are disturbingly subtle, although the
impact on the flight model was quite noticeable.

Browse at: https://www.zerobar.net/viewcvs/viewcvs.cgi?view=rev&rev=1869

Modified: trunk/csp/csplib/data/LUT.cpp
===================================================================
--- trunk/csp/csplib/data/LUT.cpp	2006-04-02 05:57:19 UTC (rev 1868)
+++ trunk/csp/csplib/data/LUT.cpp	2006-04-02 08:04:49 UTC (rev 1869)
@@ -22,6 +22,7 @@
  */
 
 #include <csp/csplib/data/LUT.h>
+#include <csp/csplib/util/Log.h>
 
 #include <sstream>
 
@@ -29,6 +30,21 @@
 CSP_NAMESPACE
 
 
+// GCC 3.4 and up require a copy constructor for const references to temporaries,
+// even if the constructor is optimized away.  In fact we want this ctor to always
+// be optimized away since the copying the vector elements is expensive.  Worse,
+// the correct implementation of the copy constructor isn't obvious because of the
+// way m_Vp is shared.  So we punt and log a fatal error if this ctor is called.
+template <int N, typename T>
+VEC<N,T>::VEC(VEC const &other): m_Vp(other.m_Vp), m_N(other.m_N) {
+	CSPLOG(FATAL, NUMERIC) << "VEC copy constructor called\n";
+	// best effort implementation, not correct in all cases:
+	//if (other.m_Vp == other.m_Vec) {
+	//	for (int i = 0; i < m_N; ++i) m_Vec[i] = other.m_Vec[i];
+	//}
+}
+
+
 /**
  *   Second derivative calculation for natural cubic spline
  *

Modified: trunk/csp/csplib/data/LUT.h
===================================================================
--- trunk/csp/csplib/data/LUT.h	2006-04-02 05:57:19 UTC (rev 1868)
+++ trunk/csp/csplib/data/LUT.h	2006-04-02 08:04:49 UTC (rev 1869)
@@ -82,6 +82,11 @@
 		}
 	}
 
+	// GCC 3.4 and up require a copy constructor for const references to temporaries,
+	// even if the constructor is optimized away.  This optimization should occur in
+	// all cases, so this ctor simply aborts if called.
+	VEC(VEC const &other);
+
 	/** Partial constructor.  See operator() for details.
 	 */
 	template <class Y>
@@ -448,6 +453,8 @@
 public:
 	/** An integer array type for dimensioning the table */
 	typedef VEC<N, int> Dim;
+	/** An integer array type for dimensioning a child table */
+	typedef VEC<N-1, int> ChildDim;
 	/** A floating point array for specifying table coordinates */
 	typedef VEC<N, X> Vec;
 	/** An array of breakpoint sets for specifying the input data coordinates */
@@ -508,7 +515,6 @@
 		return getValue(Vec(x));
 	}
 
-
 	/** Lookup the value at a given point in the table.
 	 *
 	 *  This method returns a WRAP instance which allows further coordinates to