+ /* If either stdin or stdout was closed (that is, fcntl failed),
+ then we open a dummy close-on-exec fd to occupy that slot. That
+ way, popen's internal use of pipe() will not contain either fd 0
+ or 1, overcoming the fact that the child process blindly calls
+ close() on the parent's end of the pipe without first checking
+ whether it is clobbering the fd just placed there via dup2(); the
+ exec will get rid of the dummy fd's in the child. Fortunately,
+ closed stderr in the parent does not cause problems in the
+ child. */