Made the supression of unused variables portable.

EIGEN_UNUSED is not supported on non GCC systems.

Eigen/src/Core/products/GeneralMatrixMatrix.h

@@ -160,7 +160,8 @@ static void run(Index rows, Index cols, Index depth,
   else
 #endif // EIGEN_HAS_OPENMP
   {
-    (void)info; // info is not used
+    EIGEN_UNUSED_VARIABLE(info);
+
     // this is the sequential version!
     Scalar* blockA = ei_aligned_stack_new(Scalar, kc*mc);
     std::size_t sizeB = kc*Blocking::PacketSize*Blocking::nr + kc*cols;

Eigen/src/Core/util/Macros.h

@@ -176,6 +176,9 @@
 #define EIGEN_UNUSED
 #endif
 
+// Suppresses 'unused variable' warnings.
+#define EIGEN_UNUSED_VARIABLE(var) (void)var;
+
 #if (defined __GNUC__)
 #define EIGEN_ASM_COMMENT(X)  asm("#"X)
 #else

Eigen/src/Core/util/Memory.h

@@ -218,7 +218,7 @@ inline void ei_aligned_free(void *ptr)
 **/
 inline void* ei_aligned_realloc(void *ptr, size_t new_size, size_t old_size)
 {
-  (void)old_size; // Suppress 'unused variable' warning. Seen in boost tee.
+  EIGEN_UNUSED_VARIABLE(old_size);
 
   void *result;
 #if !EIGEN_ALIGN

Eigen/src/Sparse/SparseProduct.h

@@ -382,9 +382,9 @@ struct ei_sparse_product_selector2<Lhs,Rhs,ResultType,RowMajor,ColMajor,ColMajor
   static void run(const Lhs& lhs, const Rhs& rhs, ResultType& res)
   {
       // prevent warnings until the code is fixed
-      (void) lhs;
-      (void) rhs;
-      (void) res;
+      EIGEN_UNUSED_VARIABLE(lhs);
+      EIGEN_UNUSED_VARIABLE(rhs);
+      EIGEN_UNUSED_VARIABLE(res);
 
 //     typedef SparseMatrix<typename ResultType::Scalar,RowMajor> RowMajorMatrix;
 //     RowMajorMatrix rhsRow = rhs;