pid leakage in LilyPond

[Patrick Karl]

I have noticed a resource problem in LilyPond, namely invocation of  
the "Compile/Typeset file" command in interactive mode always  
consumes one more pid.  When I enter music, I incrementally compile  
it as I go.  I do my work on a Mac running OS 10.4.  There are a  
fixed number of pids available for all the programs running on the  
Mac.  This means that as I continue to incrementally compile in  
LilyPond, the number of available pids grows less, eventually running  
out.

If LilyPond were a C program, this behavior could be caused by  
executing an "exec" call to generate a child process but not later  
waiting for the child to complete.  This means that when the child  
process does complete, it becomes what is called a zombie or defunct  
pid.  I suspect something similar is happening in LilyPond.