Issue #1234 - Rewrite internals of debug facility

src/plugin/PluginDebug.cpp

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2015 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 33 matching lines @@
       s_criticalSectionDebugLock.Unlock();
     }
   };
 
   CComAutoCriticalSection CPluginDebugLock::s_criticalSectionDebugLock;
 
   class LogText
   {
   public:
     virtual std::string Text() const = 0;
+    virtual ~LogText() {};
   };
 
   class LogTextFixed

[sergei, 2015/12/02 13:53:00]

What about naming of classes differently?

Let's add specialization of the class for the derived extending class before the
name of the base class.
DerivedClass->Class.
For example, base class:
class Text{}; // other name examples are like "Exception", "Tool", "Filter", etc
and derived class:
class FixedText: public Text{}; // "FileNotFoundException",
"OutOfMemoryException", "LogTool", "FileTool", "BlockingFilter",
"ExceptionFilter".
Pay attention that it's clear that "FilterException" is an exception and
"ExceptionFilter" is a filter. Depending on the domain "ExceptionFilter" can be
also a part of "Exception", it still works.

And for components (parts) of the class let's add the name of the part at the
end of the class name.
Class, ClassPart.
For example,
class Exception;// consists from some parts. Another example is "Filter".
The possible components of "Exception" class can be for example,
"ExceptionMessage", "ExceptionLocation", any "ExceptionPart". For `Filter` -
'FilterRule", "FilterName", "FilterAuthor".

More complex example, compare the sounding of "ExceptionFilterType" and
"TypeFilterException".

So, according to the rules above, `LogTextFixed` should be named as
`FixedLogText`.

[Eric, 2015/12/02 15:01:24]

No.

Naming the subclasses of 'class LogText' with the prefix "LogText" means that
they all appear adjacently in documentation and class browsers, which present
names in lexicographic order. This is quite useful in situations like the
present case where there's lots of small variation on a basic theme. Ordinarily
you don't include the base class name at all and use a more descriptive name. If
you feel a need to include the base class name in a subclass name, the base name
should go at the beginning.

As for prefixing members with the class name, that's a technique required for
primitive languages without proper support for scoped names. In C++, we can say
"classname::member" or "classname.member" (depending on context) if we want
name-appending behavior.

     : public LogText
   {
   protected:
     const std::string fixedText;
 
   public:
     explicit LogTextFixed(const std::string& text)
       : fixedText(text)
     {}
 
     explicit LogTextFixed(const std::exception& ex)
       : fixedText(std::string("!!! Exception: ") + ex.what())
     {}
 
     virtual std::string Text() const override

[sergei, 2015/11/30 14:15:03]

I would propose to omit `virtual` when we use `override` and always use
`override` to re-/implement any virtual method.

[Eric, 2015/11/30 17:39:01]

It's good to have both in place. Makes the intent crystal clear.

[sergei, 2015/11/30 18:14:29]

Actually, I would like to note that it's not related to this issue, we can
discuss it somewhere else, I merely wanted to attract the attention.

`virtual` was very useful until introduction of `override`, now it merely
increases the line width because `override` cannot be used for non-virtual
methods.

[Eric, 2015/12/01 20:43:58]

OK.

     {
       return fixedText;
     }
   };
 
   class LogTextErrorCode
     : public LogTextFixed
   {
   protected:
     const DWORD errorCode;
@@ skipping 20 matching lines @@
     : public SYSTEMTIME
   {
     SystemTime()
     {
       ::GetSystemTime(static_cast<SYSTEMTIME*>(this));
     }
   };
 
   class LogEntry
   {
     const std::unique_ptr<LogText> text;

[sergei, 2015/12/02 13:53:00]

Just in case, what is the reason of extensively putting const for member types?
In this particular case only std::unique_ptr is "constant" but we are still
allowed to call non-const methods of `LogText`, although there is no any one.

[Eric, 2015/12/02 15:01:24]

'const' members mean "initialized only at construction time". I use it to get
compiler assistance to prevent accidental modification of the member. 'LogEntry'
would like to be a POD (plain old data) type, but because the data has to vary,
it can't be. There's not particularly great support for variant types in C++
(unlike, say, Ada95), so we do with polymorphism.
FYI. Apropos the present case for 'LogEntry::text', I drop the 'const'
declaration on this member in the next change set. It interfered with writing a
move constructor. Arguably this is a deficiency in C++, since 'const' means
"constant for the scope beginning after member initialization and ending at the
return of the destructor" rather than "constant for the scope beginning after
the return of the constructor and before the execution of the destructor".
There's no way of expressing the latter notion.

The 'const' declaration, though, works for the present change set. No need to
change it here.

 
     std::string InitialPrefix() const
     {
       std::stringstream ss;
       ss << std::setfill('0') << std::setw(2) << st.wHour;
       ss << ":";
       ss << std::setfill('0') << std::setw(2) << st.wMinute;
       ss << ":";
       ss << std::setfill('0') << std::setw(2) << st.wSecond;
       ss << ".";
@@ skipping 56 matching lines @@
             linePosition = eolPosition + 1;
           }
         }
         out.flush();
       }
     }
 
     void WriteFile(const std::wstring& logFileName) const
     {
       std::ofstream out;
       out.open(logFileName, std::ios::app);

[sergei, 2015/12/02 13:53:00]

I wonder whether we need a synchronization here. Even later with a logging
thread which  can keep the file opened all the time, how reliable does
opening/creating of the file from multiple processes work?

[Eric, 2015/12/02 15:01:24]

Easy answer: This locking behavior is the same as it was before and as it has
been for the last few years. We seem to have had no trouble with it so far.

Behavior as-used answer: This code executes immediately upon construction of the
first BHO object, since there's a log message there. There seems to be enough
time delay in construction of the second BHO object for the file operation to
complete before a possible race.

Documentation-based answer: I believe that file open/create operations are
atomic on local Windows file systems. I could be mistaken on that, though, and I
haven't dug through documentation to find out. It's conceivable that this might
fail if ABP is installed on a network drive. Message to developers: Don't do
that. In other words, if it fails, it doesn't matter if no one's looking at the
logs.

Immediate answer: Regardless of any of the above, it's out of scope at present
as another candidate synchronization change.

       Write(out);
     }
   };
 
   std::wstring GetDataPath(const std::wstring& filename)
   {
     return GetAppDataPath() + L"\\" + filename;
   }
 
   void LogWriteDefault(const LogEntry& le)
@@ skipping 116 matching lines @@
 
 
 #ifdef ENABLE_DEBUG_RESULT_IGNORED
 
 void CPluginDebug::DebugResultIgnoring(const std::wstring& type, const std::wstring& src, const std::wstring& domain)
 {
   DebugResultFormat(L"Ignored", type, domain.empty() ? L"-" : domain, Shorten(src));
 }
 
 #endif // ENABLE_DEBUG_RESULT_IGNORED