Having worked a lot with proc fcmp lately, I think it’s fair to say that the procedure should be ‘handled with care’.

Here’s an example of one of these weird / wonderful bugs (LIN X64, 9.04.01M3P062415):

proc fcmp outlib=work.funcs.pkg;
  function test(cval $);
    file log; put cval=;
    put 'also.. you can % see % this';
    return;
  endsub;
quit;
options cmplib=work.funcs;
data null;
  x="example %";
  rc=test(x);
run;

When you look at the log, the percent symbols are missing:

cval=example
also.. you can see this

So this is strange, but it gets stranger.  If you don’t have a clean session, you will also see parts of previous messages in the log.  For instance, if you now run the exact same above code again, you get:

cval=example % see % this
also.. you can see this

So the % symbols return, in a different place!   Now, whilst this is a strange bug, it only seems to affect messages sent to the log.  So not an issue right?

Wrong..  It seems that this can cause a fatal error:

Conclusion?  Don’t send code to production that has proc fcmp writing character values to the log that may contain a % symbol!