C++14 build fixes for older gcc #2333

example/example.cpp

@@ -262,15 +262,16 @@ struct my_type
         : i(i){};
 };
 
-namespace fmt_lib = spdlog::fmt_lib;
+FMTLIB_BEGIN_NAMESPACE
 template<>
-struct fmt_lib::formatter<my_type> : fmt_lib::formatter<std::string>
+struct formatter<my_type> : formatter<std::string>
 {
     auto format(my_type my, format_context &ctx) -> decltype(ctx.out())
     {
-        return fmt_lib::format_to(ctx.out(), "[my_type i={}]", my.i);
+        return format_to(ctx.out(), "[my_type i={}]", my.i);
     }
 };
+FMTLIB_END_NAMESPACE
 
 void user_defined_example()
 {

include/spdlog/common.h

@@ -126,6 +126,13 @@ using sink_ptr = std::shared_ptr<sinks::sink>;
 using sinks_init_list = std::initializer_list<sink_ptr>;
 using err_handler = std::function<void(const std::string &err_msg)>;
 #ifdef SPDLOG_USE_STD_FORMAT
+#    ifndef FMTLIB_BEGIN_NAMESPACE
+#        define FMTLIB_BEGIN_NAMESPACE \
+           namespace std {
+#        define FMTLIB_END_NAMESPACE \
+           }
+#    endif
+
 namespace fmt_lib = std;
 
 using string_view_t = std::string_view;
@@ -146,7 +153,16 @@ template<typename... Args>
 using wformat_string_t = std::wstring_view;
 #    endif
 #    define SPDLOG_BUF_TO_STRING(x) x
+
 #else // use fmt lib instead of std::format
+
+#    ifndef FMTLIB_BEGIN_NAMESPACE
+#        define FMTLIB_BEGIN_NAMESPACE \
+           namespace fmt {
+#        define FMTLIB_END_NAMESPACE \
+           }
+#    endif
+
 namespace fmt_lib = fmt;
 
 using string_view_t = fmt::basic_string_view<char>;

include/spdlog/fmt/bin_to_hex.h

@@ -8,8 +8,10 @@
 #include <cctype>
 #include <spdlog/common.h>
 
-#if defined(__has_include) && __has_include(<version>)
-#    include <version>
+#if defined(__has_include)
+#    if __has_include(<version>)
+#        include <version>
+#    endif
 #endif
 
 #if __cpp_lib_span >= 202002L