Support logging of std::error_code

CMakeLists.txt

@@ -314,6 +314,7 @@ add_example(TscClock)
   add_inttest(LoggingTimePoint)
   add_inttest(LoggingEnums)
   add_inttest(LoggingAdaptedStructs)
+  add_inttest(LoggingErrorCode)
   add_inttest(NamedWriters)
   add_inttest(SeverityControl)
   add_inttest(Categories)

doc/UserGuide.md

@@ -201,6 +201,14 @@ The pretty printed text format is affected by the `-d` flag when using [bread](#
 If `%d` (localtime) appears first in the `-f` (format) parameter, the time point is converted to producer-local timezone
 (this is the default). If `%u` (UTC) appears first, the time point is shown in UTC.
 
+### error_code
+
+`std::error_code` objects can be logged after adoption by including a header file:
+
+    [catchfile test/integration/LoggingErrorCode.cpp ec]
+
+The error code is serialized in terms of the `message` member, therefore it may result in memory allocations.
+
 ### optional
 
 If C++17 is available, the standard optional with a loggable `value_type` can be made loggable:

include/binlog/PrettyPrinter.cpp

@@ -147,8 +147,9 @@ bool PrettyPrinter::printStruct(detail::OstreamBuffer& out, mserialize::Visitor:
   }
 
   if ((sb.name == "std::filesystem::path" && sb.tag == "`str'[c")
-  || (sb.name == "std::filesystem::directory_entry" && sb.tag == "`path'{std::filesystem::path`str'[c}"))
-  {
+  || (sb.name == "std::filesystem::directory_entry" && sb.tag == "`path'{std::filesystem::path`str'[c}")
+  || (sb.name == "std::error_code" && sb.tag == "`message'[c")
+  ) {
     const std::uint32_t size = input.read<std::uint32_t>();
     out.write(input.view(size), size);
     return true;

include/binlog/adapt_stderrorcode.hpp

@@ -0,0 +1,10 @@
+#ifndef BINLOG_ADAPT_STDERRORCODE_HPP
+#define BINLOG_ADAPT_STDERRORCODE_HPP
+
+// Make std::error_code loggable by including this file
+
+#include <binlog/adapt_struct.hpp>
+
+BINLOG_ADAPT_STRUCT(std::error_code, message)
+
+#endif // BINLOG_ADAPT_STDERRORCODE_HPP

test/integration/IntegrationTest.cpp

@@ -112,6 +112,7 @@ TEST_CASE("LoggingTuples")         { runReadDiff("LoggingTuples", "%m"); }
 TEST_CASE("LoggingEnums")          { runReadDiff("LoggingEnums", "%m"); }
 TEST_CASE("LoggingAdaptedStructs") { runReadDiff("LoggingAdaptedStructs", "%m"); }
 TEST_CASE("LoggingTimePoint")      { runReadDiff("LoggingTimePoint", "%m"); }
+TEST_CASE("LoggingErrorCode")      { runReadDiff("LoggingErrorCode", "%m"); }
 TEST_CASE("NamedWriters")          { runReadDiff("NamedWriters", "%n %m"); }
 TEST_CASE("SeverityControl")       { runReadDiff("SeverityControl", "%S %m"); }
 TEST_CASE("Categories")            { runReadDiff("Categories", "%C %n %m"); }

test/integration/LoggingErrorCode.cpp

@@ -0,0 +1,36 @@
+//[ec
+#include <binlog/adapt_stderrorcode.hpp> // must be included to log std::error_code
+//]
+
+#include <binlog/binlog.hpp>
+
+#include <iostream>
+#include <string>
+#include <system_error>
+
+class error_category : public std::error_category
+{
+public:
+  const char* name() const noexcept override { return "error_category"; }
+  std::string message(int) const override { return "Success"; }
+};
+
+int main()
+{
+  //[ec
+
+  std::error_code ec;
+  //]
+
+  // Use a custom error category to make sure the message is platform-agnostic
+  error_category category;
+  ec.assign(0, category);
+
+  //[ec
+  BINLOG_INFO("ec: {}", ec);
+  // Outputs: ec: Success
+  //]
+
+  binlog::consume(std::cout);
+  return 0;
+}