Fix building when using C++11

Update changelog

src/algorithms/libs/CMakeLists.txt

@@ -31,6 +31,7 @@ set(GNSS_SPLIBS_SOURCES
     item_type_helpers.cc
     pass_through.cc
     short_x2_to_cshort.cc
+    gnss_sdr_string_literals.cc
 )
 
 set(GNSS_SPLIBS_HEADERS
@@ -61,6 +62,7 @@ set(GNSS_SPLIBS_HEADERS
     item_type_helpers.h
     pass_through.h
     short_x2_to_cshort.h
+    gnss_sdr_string_literals.h
 )
 
 if(ENABLE_OPENCL)

src/algorithms/libs/gnss_sdr_string_literals.cc

@@ -0,0 +1,37 @@
+/*!
+ * \file gnss_sdr_string_literals.cc
+ * \brief This file implements the ""s operator for std::string in C++11, and
+ * puts it into the std::string_literals namespace. This is already implemented
+ * in C++14, so this is only compiled when using C++11. The .cc file is required
+ * for avoiding the duplication of symbols.
+ *
+ * \author Carles Fernandez-Prades, 2021. cfernandez(at)cttc.es
+ *
+ *
+ * -----------------------------------------------------------------------------
+ *
+ * GNSS-SDR is a Global Navigation Satellite System software-defined receiver.
+ * This file is part of GNSS-SDR.
+ *
+ * Copyright (C) 2010-2021  (see AUTHORS file for a list of contributors)
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ * -----------------------------------------------------------------------------
+ */
+
+#include "gnss_sdr_string_literals.h"
+
+#if __cplusplus == 201103L
+
+namespace std
+{
+namespace string_literals
+{
+std::string operator"" s(const char* str, std::size_t len)
+{
+    return std::string(str, len);
+};
+}  // namespace string_literals
+}  // namespace std
+
+#endif  // __cplusplus == 201103L

src/algorithms/libs/gnss_sdr_string_literals.h

@@ -0,0 +1,48 @@
+/*!
+ * \file gnss_sdr_string_literals.h
+ * \brief This file implements the ""s operator for std::string in C++11, and
+ * puts it into the std::string_literals namespace. This is already implemented
+ * in C++14, so this is only compiled when using C++11. The .cc file is required
+ * for avoiding the duplication of symbols.
+ *
+ * \author Carles Fernandez-Prades, 2021. cfernandez(at)cttc.es
+ *
+ *
+ * -----------------------------------------------------------------------------
+ *
+ * GNSS-SDR is a Global Navigation Satellite System software-defined receiver.
+ * This file is part of GNSS-SDR.
+ *
+ * Copyright (C) 2010-2021  (see AUTHORS file for a list of contributors)
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ * -----------------------------------------------------------------------------
+ */
+
+#ifndef GNSS_SDR_STRING_LITERALS_H
+#define GNSS_SDR_STRING_LITERALS_H
+
+/** \addtogroup Algorithms_Library
+ * \{ */
+/** \addtogroup Algorithm_libs algorithms_libs
+ * \{ */
+
+#if __cplusplus == 201103L
+
+#include <cstddef>
+#include <string>
+
+namespace std
+{
+namespace string_literals
+{
+std::string operator"" s(const char* str, std::size_t len);
+}  // namespace string_literals
+}  // namespace std
+
+#endif  // __cplusplus == 201103L
+
+/** \} */
+/** \} */
+
+#endif  // GNSS_SDR_STRING_LITERALS_H