Why doesn't this work?

vining · November 2006

DEFINE_START

nVST_DeBug = 0 ;  // use to debug from start up!  change to 0 when finished debugging!
if (nVST_DeBug)   // or comment out completely !
     {
     #WARN 'nVST_DeBug is set to 1 in DEFINE_START' ;
     }

No matter what I change nVST_DeBug to I get the compiler warning, which is not what I expected!

Why?

Joe Hebert · November 2006

The short answer is because that?s its job. It?s a precompile directive. Unless there is some other precompile directive wrapped around it (i.e. #IF_DEFINED, #IF_NOT_DEFINED, etc.) the warning message will be generated at compile time. The compiler doesn?t evaluate IF conditions. IF conditions are evaluated at run-time. Precompile directives are not evaluated at run-time, they are evaluated at compile time.

Joe Hebert · November 2006

As a follow up, you could do something like this:

Debug is on and will generate your warning ? at compile time

DEFINE_CONSTANT

INTEGER nDebugOff = 0
INTEGER nDebugOn  = 1

DEFINE_VARIABLE

INTEGER nDebug

DEFINE_START

nDebug = nDebugOn

#IF_DEFINED nDebugOn
   #WARN 'Debug in On'
#END_IF

And to turn debug off and not have the warning generated you could do this:

DEFINE_CONSTANT

INTEGER nDebugOff = 0
//INTEGER nDebugOn  = 1

DEFINE_VARIABLE

INTEGER nDebug

DEFINE_START

nDebug = nDebugOff

#IF_DEFINED nDebugOn
   #WARN 'Debug in On'
#END_IF

HTH

DHawthorne · November 2006

It should be noted that Joe's examples require a re-compile to turn the debug flag on and off, you can't use precompiler directives on-the-fly.

I've found it simpler to use SEND_STRING 0 coupled with a regular variable (or virtual device channel). Precompiler directives are a bit kludgy for this kind of application, IMO.

Joe Hebert · November 2006

DHawthorne wrote:

It should be noted that Joe's examples require a re-compile to turn the debug flag on and off, you can't use precompiler directives on-the-fly.

Yes, you do have to recompile if you modify source code.

Isn?t that what this thread is about ? compile time? Thought I did note that:

me wrote:

Precompile directives are not evaluated at run-time, they are evaluated at compile time.

DHawthorne wrote:

I've found it simpler to use SEND_STRING 0 coupled with a regular variable (or virtual device channel). Precompiler directives are a bit kludgy for this kind of application, IMO.

Agreed. The example is there to show how the directive works answering the original question posed. A debug channel normally suffices for me too.

vining · November 2006

Joe wrote:

Unless there is some other precompile directive wrapped around it (i.e. #IF_DEFINED, #IF_NOT_DEFINED, etc.)

That's what I suspected.

DHawthorne wrote:

I've found it simpler to use SEND_STRING 0 coupled with a regular variable (or virtual device channel). Precompiler directives are a bit kludgy for this kind of application, IMO.

I have a regular debug variable used through out the code as a conditon for enabling or disabling my SEND_STRING 0's which is the var nVST_DeBug. I just wanted a lazy mans way of starting debug at start up just so I can see all the initialization stuff that I would miss if I'm slow on the trigger. The #WARN was put there as a reminder that I set it in DEFINE_START and not by setting a variable or channel.

Why doesn't this work?

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