free in C++?

Is malloc_options supposed to work in C++?  I have this message:

astream in free(): warning: junk pointer, too high to make sense.

My code doesn't call free().  It calls the delete operator, but this
message is not consequent to my deletes, if gdb is to be believed.  

The free manpage indicates this is a libc diagnostic.  Trying to follow
directions, I put 

	extern char *malloc_options;
	malloc_options = "X";

in the main module.  That seems like it should be enough, but to make sure
I also export MALLOC_OPTIONS=X in the shell.  Yet the behavior doesn't
change.  

I'd like to use MALLOC_OPTIONS=X or similar to trap it.  

Suggestions?  

--jkl