Adapt to fmt's deprecation of format_to memory buffer overload

This reverts commit ba7da2f79a.

Jenkinsfile

@@ -63,6 +63,7 @@ pipeline{
             [os: 'fedora', ver: '33',    arch: 'x86_64', compiler: 'gcc-10'],
             [os: 'fedora', ver: '34',    arch: 'x86_64', compiler: 'gcc-11'],
             [os: 'macos',  ver: '11',    arch: 'x86_64', compiler: 'apple-clang-12'],
+            [os: 'macos',  ver: '11',    arch: 'arm64',  compiler: 'apple-clang-13'],
           ])
 
           parallel(builds)

logger/Logger.cxx

@@ -15,6 +15,7 @@
 
 #include <cstdio> // printf
 #include <iostream>
+#include <iterator> // std::back_inserter
 
 using namespace std;
 
@@ -160,27 +161,27 @@ Logger::Logger(Severity severity, Verbosity verbosity, const string& file, const
             for (const auto info : spec.fInfos) {
                 switch (info) {
                     case VSpec::Info::process_name:
-                        fmt::format_to(fBWPrefix, "[{}]", fInfos.process_name);
+                        fmt::format_to(std::back_inserter(fBWPrefix), "[{}]", fInfos.process_name);
                         break;
                     case VSpec::Info::timestamp_us:
                         FillTimeInfos();
-                        fmt::format_to(fBWPrefix, "[{:%H:%M:%S}.{:06}]", fmt::localtime(fInfos.timestamp), fInfos.us.count());
+                        fmt::format_to(std::back_inserter(fBWPrefix), "[{:%H:%M:%S}.{:06}]", fmt::localtime(fInfos.timestamp), fInfos.us.count());
                         break;
                     case VSpec::Info::timestamp_s:
                         FillTimeInfos();
-                        fmt::format_to(fBWPrefix, "[{:%H:%M:%S}]", fmt::localtime(fInfos.timestamp));
+                        fmt::format_to(std::back_inserter(fBWPrefix), "[{:%H:%M:%S}]", fmt::localtime(fInfos.timestamp));
                         break;
                     case VSpec::Info::severity:
-                        fmt::format_to(fBWPrefix, "[{}]", fInfos.severity_name);
+                        fmt::format_to(std::back_inserter(fBWPrefix), "[{}]", fInfos.severity_name);
                         break;
                     case VSpec::Info::file_line_function:
-                        fmt::format_to(fBWPrefix, "[{}:{}:{}]", fInfos.file, fInfos.line, fInfos.func);
+                        fmt::format_to(std::back_inserter(fBWPrefix), "[{}:{}:{}]", fInfos.file, fInfos.line, fInfos.func);
                         break;
                     case VSpec::Info::file_line:
-                        fmt::format_to(fBWPrefix, "[{}:{}]", fInfos.file, fInfos.line);
+                        fmt::format_to(std::back_inserter(fBWPrefix), "[{}:{}]", fInfos.file, fInfos.line);
                         break;
                     case VSpec::Info::file:
-                        fmt::format_to(fBWPrefix, "[{}]", fInfos.file);
+                        fmt::format_to(std::back_inserter(fBWPrefix), "[{}]", fInfos.file);
                         break;
                     default:
                         break;
@@ -188,7 +189,7 @@ Logger::Logger(Severity severity, Verbosity verbosity, const string& file, const
             }
 
             if (spec.fSize > 0) {
-                fmt::format_to(fBWPrefix, " ");
+                fmt::format_to(std::back_inserter(fBWPrefix), " ");
             }
         }
 
@@ -196,27 +197,27 @@ Logger::Logger(Severity severity, Verbosity verbosity, const string& file, const
             for (const auto info : spec.fInfos) {
                 switch (info) {
                     case VSpec::Info::process_name:
-                        fmt::format_to(fColorPrefix, "[{}]", ColorOut(Color::fgBlue, fInfos.process_name));
+                        fmt::format_to(std::back_inserter(fColorPrefix), "[{}]", ColorOut(Color::fgBlue, fInfos.process_name));
                         break;
                     case VSpec::Info::timestamp_us:
                         FillTimeInfos();
-                        fmt::format_to(fColorPrefix, "[{}{:%H:%M:%S}.{:06}{}]", startColor(Color::fgCyan), fmt::localtime(fInfos.timestamp), fInfos.us.count(), endColor());
+                        fmt::format_to(std::back_inserter(fColorPrefix), "[{}{:%H:%M:%S}.{:06}{}]", startColor(Color::fgCyan), fmt::localtime(fInfos.timestamp), fInfos.us.count(), endColor());
                         break;
                     case VSpec::Info::timestamp_s:
                         FillTimeInfos();
-                        fmt::format_to(fColorPrefix, "[{}{:%H:%M:%S}{}]", startColor(Color::fgCyan), fmt::localtime(fInfos.timestamp), endColor());
+                        fmt::format_to(std::back_inserter(fColorPrefix), "[{}{:%H:%M:%S}{}]", startColor(Color::fgCyan), fmt::localtime(fInfos.timestamp), endColor());
                         break;
                     case VSpec::Info::severity:
-                        fmt::format_to(fColorPrefix, "[{}]", GetColoredSeverityString(fInfos.severity));
+                        fmt::format_to(std::back_inserter(fColorPrefix), "[{}]", GetColoredSeverityString(fInfos.severity));
                         break;
                     case VSpec::Info::file_line_function:
-                        fmt::format_to(fColorPrefix, "[{}:{}:{}]", ColorOut(Color::fgBlue, fInfos.file), ColorOut(Color::fgYellow, fInfos.line), ColorOut(Color::fgBlue, fInfos.func));
+                        fmt::format_to(std::back_inserter(fColorPrefix), "[{}:{}:{}]", ColorOut(Color::fgBlue, fInfos.file), ColorOut(Color::fgYellow, fInfos.line), ColorOut(Color::fgBlue, fInfos.func));
                         break;
                     case VSpec::Info::file_line:
-                        fmt::format_to(fColorPrefix, "[{}:{}]", ColorOut(Color::fgBlue, fInfos.file), ColorOut(Color::fgYellow, fInfos.line));
+                        fmt::format_to(std::back_inserter(fColorPrefix), "[{}:{}]", ColorOut(Color::fgBlue, fInfos.file), ColorOut(Color::fgYellow, fInfos.line));
                         break;
                     case VSpec::Info::file:
-                        fmt::format_to(fColorPrefix, "[{}]", ColorOut(Color::fgBlue, fInfos.file));
+                        fmt::format_to(std::back_inserter(fColorPrefix), "[{}]", ColorOut(Color::fgBlue, fInfos.file));
                         break;
                     default:
                         break;
@@ -224,7 +225,7 @@ Logger::Logger(Severity severity, Verbosity verbosity, const string& file, const
             }
 
             if (spec.fSize > 0) {
-                fmt::format_to(fColorPrefix, " ");
+                fmt::format_to(std::back_inserter(fColorPrefix), " ");
             }
         }
 

logger/Logger.h

@@ -26,6 +26,7 @@
 
 #include <fmt/core.h>
 #include <fmt/printf.h>
+#include <fmt/ostream.h>
 
 #pragma GCC diagnostic pop
 
@@ -68,19 +69,19 @@ enum class Severity : int
     // aliases
     warning = warn,
     // backwards-compatibility
-    NOLOG   [[deprecated("Use 'nolog' instead")]]   = nolog,
-    TRACE   [[deprecated("Use 'trace' instead")]]   = trace,
-    DEBUG4  [[deprecated("Use 'debug4' instead")]]  = debug4,
-    DEBUG3  [[deprecated("Use 'debug3' instead")]]  = debug3,
-    DEBUG2  [[deprecated("Use 'debug2' instead")]]  = debug2,
-    DEBUG1  [[deprecated("Use 'debug1' instead")]]  = debug1,
-    DEBUG   [[deprecated("Use 'debug' instead")]]   = debug,
-    INFO    [[deprecated("Use 'info' instead")]]    = info,
-    STATE   [[deprecated("Use 'state' instead")]]   = state,
-    WARNING [[deprecated("Use 'warning' instead")]] = warn,
-    WARN    [[deprecated("Use 'warn' instead")]]    = warn,
-    ERROR   [[deprecated("Use 'error' instead")]]   = error,
-    FATAL   [[deprecated("Use 'fatal' instead")]]   = fatal
+    NOLOG __attribute__((deprecated("Use LOG(nolog) instead (lowercase severity name)."))) = nolog,
+    FATAL __attribute__((deprecated("Use LOG(fatal) instead (lowercase severity name)."))) = fatal,
+    ERROR __attribute__((deprecated("Use LOG(error) instead (lowercase severity name)."))) = error,
+    WARN __attribute__((deprecated("Use LOG(warn) instead (lowercase severity name)."))) = warn,
+    WARNING __attribute__((deprecated("Use LOG(warning) instead (lowercase severity name)."))) = warn,
+    STATE __attribute__((deprecated("Use LOG(state) instead (lowercase severity name)."))) = state,
+    INFO __attribute__((deprecated("Use LOG(info) instead (lowercase severity name)."))) = info,
+    DEBUG __attribute__((deprecated("Use LOG(debug) instead (lowercase severity name)."))) = debug,
+    DEBUG1 __attribute__((deprecated("Use LOG(debug1) instead (lowercase severity name)."))) = debug1,
+    DEBUG2 __attribute__((deprecated("Use LOG(debug2) instead (lowercase severity name)."))) = debug2,
+    DEBUG3 __attribute__((deprecated("Use LOG(debug3) instead (lowercase severity name)."))) = debug3,
+    DEBUG4 __attribute__((deprecated("Use LOG(debug4) instead (lowercase severity name)."))) = debug4,
+    TRACE __attribute__((deprecated("Use LOG(trace) instead (lowercase severity name)."))) = trace
 };
 
 // verbosity levels: