[lmi-commits] [lmi] master b538769 6/8: Use std::endian when using C++20

[Greg Chicares]

branch: master
commit b538769eccbdf7819444801ef6c7b481cde51211
Author: Vadim Zeitlin <vadim@tt-solutions.com>
Commit: Gregory W. Chicares <gchicares@sbcglobal.net>

    Use std::endian when using C++20
    
    Also check for the value of __cplusplus corresponding to C++20.
    
    This fixes compilation with C++20 compilers.
---
 actuarial_table.cpp |  9 +++++----
 rate_table.cpp      | 20 ++++++++++++++------
 2 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/actuarial_table.cpp b/actuarial_table.cpp
index 6a9ab14..e9edad5 100644
--- a/actuarial_table.cpp
+++ b/actuarial_table.cpp
@@ -37,12 +37,14 @@
 #include <boost/filesystem/path.hpp>
 
 #include <algorithm>                    // max(), min()
+#if 202002 <= __cplusplus
+#   include <bit>                       // endian
+#endif //  202002 <= __cplusplus
 #include <cctype>                       // toupper()
 #include <cstdint>
 #include <ios>
 #include <istream>
 #include <limits>
-#include <type_traits>                  // endian
 
 namespace
 {
@@ -92,10 +94,9 @@ actuarial_table::actuarial_table(std::string const& 
filename, int table_number)
 {
     // Binary tables in the SOA format are not portable; this code
     // presumably works only on little-endian hardware.
-#if 201900L < __cplusplus
-    #error Use the proper C++20 value, which was unknown when this was written.
+#if 202002 <= __cplusplus
     static_assert(std::endian::native == std::endian::little);
-#endif // 201900L < __cplusplus
+#endif // 202002 <= __cplusplus
 
     if(table_number_ <= 0)
         {
diff --git a/rate_table.cpp b/rate_table.cpp
index 82ab99a..93260fa 100644
--- a/rate_table.cpp
+++ b/rate_table.cpp
@@ -35,6 +35,9 @@
 #include <boost/filesystem/fstream.hpp>
 
 #include <algorithm>                    // count()
+#if 202002 <= __cplusplus
+#   include <bit>                       // endian
+#endif //  202002 <= __cplusplus
 #include <climits>                      // ULLONG_MAX
 #include <cstdlib>                      // strtoull()
 #include <cstring>                      // memcpy(), strncmp()
@@ -68,9 +71,17 @@
 // different from their in memory representation.
 static_assert(std::numeric_limits<double>::is_iec559);
 
-#if 201900L < __cplusplus
-    #error Use std::endian instead when it becomes available.
-#endif // 201900L < __cplusplus
+// Check that WORDS_BIGENDIAN, which is supposed to be defined in makefile/at
+// the compiler command line if necessary, is consistent with the actual
+// endianness used.
+#if 202002 <= __cplusplus
+#   if defined WORDS_BIGENDIAN
+static_assert(std::endian::native == std::endian::big);
+#   else  // !defined WORDS_BIGENDIAN
+static_assert(std::endian::native == std::endian::little);
+#   endif // !defined WORDS_BIGENDIAN
+#endif // !(202002 <= __cplusplus)
+
 // Helper functions used to swap bytes on big endian platforms.
 namespace
 {
@@ -83,9 +94,6 @@ std::uint8_t swap_bytes_if_big_endian(std::uint8_t val)
     return val;
 }
 
-// We rely on makefile defining WORDS_BIGENDIAN on big endian architectures,
-// conversions from little endian format are only needed there and are trivial
-// on little endian machines.
 #if defined WORDS_BIGENDIAN
 inline
 std::uint16_t swap_bytes_if_big_endian(std::uint16_t val)