#define a line comment symbol (//) - possible?

[terminalstat]

I was just curious: for debugging purposes I want some of Print() functions to be commented at once. Here's my approach that does not work:

#define DEBUG // -debug switcher, comment line for production

//debug printer:
#ifdef DEBUG
   #define DB //
#else
   #define DB 
#endif 

DB Print("some debug info.."); 

//want to replace DB -> "//" in case DEBUG is defined, so compiler see:

// Print("some debug info.."); 

Is it possible with MQL5?

PS: I've read https://www.mql5.com/en/articles/654 but want exactly above approach.

Thank's

[Alain Verleyen]

terminalstat:

I was just curious: for debugging purposes I want some of Print() functions to be commented at once. Here's my approach that does not work:

Is it possible with MQL5?

PS: I've read https://www.mql5.com/en/articles/654 but want exactly above approach.

Thank's

Of course not.

#define DEBUG // -debug switcher, comment line for production

#ifdef DEBUG Print("some debug info.."); #endif 

[William Roeder]

1. Comments are stripped before processing the tokens (#define) so no.
   

2. #ifdef DEBUG    #define DB // This will not work, same in either case. #else    #define DB #endif
   #ifdef DEBUG    #define DB true #else    #define DB false #endif if(DB) Print("some debug info.."); else …

   
   

[lippmaje]

You can use a #define to switch logging on altogether like so:

#define DEBUG // comment out with '//' when done

#ifdef DEBUG
  #define DebugPrint(s) Print(s)
#else
  #define DebugPrint(s)
#endif

void OnTick() {
   ...
   DebugPrint("debug idx="+(string)idx);
}

It will become even more advanced if you introduce a log level.

[terminalstat]

Usual ways  takes too much typing, anyway thanks for your time!

William Roeder: all those "if" would stay in compiled code, even if DEBUG is not defined, correct? That would impact execution speed.

[William Roeder]

terminalstat: William Roeder: all those "if" would stay in compiled code, even if DEBUG is not defined, correct? That would impact execution speed.

Should be removed at the optimization stage. Don't assume — profile it.

[lippmaje]

terminalstat:

Usual ways  takes too much typing, anyway thanks for your time!

The brute force solution. You'll get "some expression has no effect" warnings, but no need to change any line of code.

#define DEBUG // comment out with '//' when done
#ifdef DEBUG
#else
  #define Print false&&""==StringFormat
#endif

[terminalstat]

lippmaje:

The brute force solution. You'll get "some expression has no effect" warnings, but no need to change any line of code.

it does not compile with first line commented out:

//#define DEBUG // comment out with '//' when done
#ifdef DEBUG
#else
  #define Print false&&""==StringFormat
#endif

'test.mq5'      test.mq5        1       1
'DefineGlobal.mqh'      DefineGlobal.mqh        1       1
'StringFormat' - wrong parameters count test.mq5        18      1
result of expression not used   test.mq5        18      1
'StringFormat' - wrong parameters count test.mq5        19      1
result of expression not used   test.mq5        19      1
'StringFormat' - wrong parameters count test.mq5        20      4
result of expression not used   test.mq5        20      4

[lippmaje]

terminalstat:

it does not compile with first line commented out:

Looks like I overlooked your answer, sorry.

Yes, unfortunately this doesn't compile in all places.

Try this instead:

  #define Print while(false)Print

There's a small chance to break the code with statements like this

  int i=0;
  do
    Print(i);
  while(++i<10);

But it's rather uncommon to occur.

Edit:

This looks better

#define DEBUG // comment out with '//' when done
#ifdef DEBUG
#else
  #define Print for(;false;)Print
#endif

And the executable is getting smaller with the substitution - that means the optimizer was able to recognize and remove the empty statements.