#macro Elipsis and #if not working together

[wallyg]

Or I have a total misunderstanding of this

using C:\FB\WinFBE_Suite\FreeBASIC-1.06.0\fbc -g -s gui -mt "fbSIR.bas"

I have a macro

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#Macro   Signal(Name,Detail,RetValue,Arguments...)
	.
	.
	.
    SignalArgument(Arguments)
    propNofSignals += 1
#EndMacro
#Macro   SignalArgument(TofArg,NofArg,IsPointer,Arguments...)
	.
	.
	.
#Print /#arguments/
#If (Len(#Arguments) > 0)
    SignalArgument(Arguments)
#EndIf 
#EndMacro

This seems to work stripping off the first 3 arguments and recursively processing the remaining arguments

However when it finally gets to the point that the argument Arguments is empty, Signal(Arguments) is still called and causes an error due to invalid arguments being passed (of course, Arguments is the empty string)

During the recursive calls the #print /#Arguments/ statement prints shorter and shorter lists of arguments, and then eventually it prints /""/ which should stop calling SignalArgument. But it does not.

I also tried

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#if (#Arguments <> "")

And that also causes SignalArgument to be called 1 time to many.

This seemed pretty straight forward when I read it in the documentation. What have I misunderstood?

[Tourist Trap]

Hello,

sorry , even if I've done macros with ellipsis in the past, like here:
viewtopic.php?f=7&t=25149&p=225712#p225712

I still can't help you because you don't show an example (or I dont see it...) of usage of your macro. What is the syntax of the call, what objects do you pass, what do you want as result??

Anyway, at first sight I would say that you should not try to test dynamic content with #IF. Use a normal IF instead with variables created in your macro, in a scope block for instance. I say that with not 100% of certainty. Look at my example rather. You probably will find how to adapt it to your issue. Otherwise post a more complete question :)

[coderJeff]

Good find, wallyg. This is part feature request & part bug.

fbc does not support recursive #macro or #define, but also doesn't error in non-trivial cases either.

Example #1, simulates what we are trying to do:

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#macro MX( X, args... )
	#print "   MX()"
	#print "      X    = " #X
	#print "      args = " #args
	#if len( #args ) > 0
		#print "      len(" #args) > 0"
	#else
		#print "      len(" #args) = 0"
	#endif
#endmacro

#macro M( X, args... )
	#print "M()"
	#print "   X    = " #X
	#print "   args = " #args
	MX(X, args )
#endmacro

M(A,B,C)
M(A,B)
M(A)

Output:

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M()
   X    =  $"A"
   args =  $"B,C"
   MX()
      X    =  $"A"
      args =  $"B,C"
      len( $"B,C") >0"
M()
   X    =  $"A"
   args =  $"B"
   MX()
      X    =  $"A"
      args =  $"B"
      len( $"B") >0"
M()
   X    =  $"A"
   args =  ""
   MX()
      X    =  $"A"
      args =  ""
      len( "") =0"

Example #2, directly add recursion. fbc can detect this trivial form of #macro recursion and generates an error:

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#macro MX( X, args... )
	#print "   MX()"
	#print "      X    = " #X
	#print "      args = " #args
	#if len( #args ) > 0
		#print "      len(" #args) > 0"
		MX(args)
	#else
		#print "      len(" #args) = 0"
	#endif
#endmacro

#macro M( X, args... )
	#print "M()"
	#print "   X    = " #X
	#print "   args = " #args
	MX(X, args )
#endmacro

M(A,B,C)

Output:

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M()
   X    =  $"A"
   args =  $"B,C"
   MX()
      X    =  $"A"
      args =  $"B,C"
      len( $"B,C") >0"
macro.bas(20) error 89: Recursive DEFINE not allowed, found 'MX' in 'M(A,B,C)'
macro.bas(20) error 3: Expected End-of-Line, found '#' in 'M(A,B,C)'
      len( $"B,C") =0"

Example #3, adding the #if tricks fbc (it doesn't detect the recursion), and actually causes fbc to hang, never ending it's own internal recursive expansion of MX() -- BUG

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#macro MX( X, args... )
	#print "   MX()"
	#print "      X    = " #X
	#print "      args = " #args
	#if len( #args ) > 0
		#print "      len(" #args ) > 0
		MX(args)
	#else
		#print "      len(" #args ) = 0
	#endif
#endmacro

#macro M( X, args... )
	#print "M()"
	#print "   X    = " #X
	#print "   args = " #args
	#if len( #args ) > 0
		#print "   len(" #args ) > 0
		MX(X, args )
	#endif
#endmacro

M(A,B,C)

Output:

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M()
   X    =  $"A"
   args =  $"B,C"
   len( $"B,C" ) >0
   MX()
      X    =  $"A"
      args =  $"B,C"
      len( $"B,C" ) >0
   MX()
      X    =  $"B"
      args =  $"C"
      len( $"C" ) >0
   MX()
      X    =  $"C"
      args =  ""
... hang forever ....

I couldn't come up with a work-around. Either fbc should track the macro expansions and error (bug), or allow recursion (feature). Though if macro recursion were allowed, it should eventually error on some maximum depth, otherwise, it would just crash the compiler.