Add empty streaming operator, so that std::cout << SMatrixGPU() does not fail

Author: davidrohr

Common/MathUtils/include/MathUtils/SMatrixGPU.h

@@ -29,6 +29,7 @@
 #include "GPUCommonMath.h"
 #include "GPUCommonAlgorithm.h"
 #include "GPUCommonLogger.h"
+#include "GPUCommonTypeTraits.h"
 
 namespace o2::math_utils::detail
 {
@@ -468,6 +469,9 @@ class SMatrixGPU
   GPUd() const T& operator()(unsigned int i, unsigned int j) const;
   GPUd() T& operator()(unsigned int i, unsigned int j);
 
+  template <typename Y, typename X>
+  GPUd() friend X& operator<<(Y& y, const SMatrixGPU&);
+
   class SMatrixRowGPU
   {
    public:
@@ -512,6 +516,13 @@ class SMatrixGPU
   R mRep;
 };
 
+template <class T, unsigned int D1, unsigned int D2, class R, typename Y, typename X = Y>
+  requires(sizeof(typename X::traits_type::pos_type) != 0) // do not provide a template to fair::Logger, etc... (pos_type is a member type of all std::ostream classes)
+GPUd() X& operator<<(Y& y, const SMatrixGPU<T, D1, D2, R>&)
+{
+  return y;
+}
+
 template <class T, unsigned int D1, unsigned int D2, class R>
 GPUdi() SMatrixGPU<T, D1, D2, R>::SMatrixGPU(SMatrixIdentity)
 {