const qualifiers

[kamocat]

I have all the errors taken care of except this one:

Arduino: 1.8.12 (Linux), Board: "Adafruit Feather M0, Arduino, Off"

In file included from /home/marshal/Arduino/libraries/Plog/include/plog/Appenders/IAppender.h:2:0,
                 from /home/marshal/Arduino/libraries/Plog/include/plog/Logger.h:2,
                 from /home/marshal/Arduino/libraries/Plog/include/plog/Log.h:7,
                 from /home/marshal/Arduino/libraries/Plog/Plog.h:1,
                 from /home/marshal/Arduino/libraries/Plog/examples/hello/hello.ino:1:
/home/marshal/Arduino/libraries/Plog/include/plog/Appenders/../Record.h: In member function 'virtual const nchar* plog::Record::getMessage() const':
/home/marshal/Arduino/libraries/Plog/include/plog/Appenders/../Record.h:258:34: error: passing 'const nostringstream {aka const obufstream}' as 'this' argument discards qualifiers [-fpermissive]
             return m_message.buf();
                                  ^
In file included from /home/marshal/Arduino/libraries/SdFat/src/FatLib/ArduinoStream.h:33:0,
                 from /home/marshal/Arduino/libraries/SdFat/src/sdios.h:32,
                 from /home/marshal/Arduino/libraries/SdFat/src/SdFat.h:36,
                 from /home/marshal/Arduino/libraries/Plog/include/plog/Appenders/../Util.h:6,
                 from /home/marshal/Arduino/libraries/Plog/include/plog/Appenders/../Record.h:4,
                 from /home/marshal/Arduino/libraries/Plog/include/plog/Appenders/IAppender.h:2,
                 from /home/marshal/Arduino/libraries/Plog/include/plog/Logger.h:2,
                 from /home/marshal/Arduino/libraries/Plog/include/plog/Log.h:7,
                 from /home/marshal/Arduino/libraries/Plog/Plog.h:1,
                 from /home/marshal/Arduino/libraries/Plog/examples/hello/hello.ino:1:
/home/marshal/Arduino/libraries/SdFat/src/FatLib/bufstream.h:123:9: note:   in call to 'char* obufstream::buf()'
   char* buf() {
         ^~~
exit status 1
Error compiling for board Adafruit Feather M0.

This report would have more information with
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option enabled in File -> Preferences.

If I remove the const qualifier, however, the function call doesn't match because the compiler thinks that the object is going to be modified. All we're doing is getting access to the character buffer inside the obufstream, to stream it to another destination.

[prototypicalpro]

By removing the const qualifier on the original addMessage and then creating a const overload which calls the non-const version, I was able to fix the issue. My changes are in https://github.com/kamocat/plog/pull/2.

[kamocat]

Looks good, thank you.