$(shell ...) exit status

[M L Dymski]

How does one determine the exit status of the shell forked by $(shell ...)? I see nothing about it in the 3.81 online manual. I need to run a command for which the null string is a perfectly reasonable output value, so I can't get away with anything like this:

foo     :=      $(shell mycommand)

ifeq($foo),)
<code to handle error conditions>
endif

And I don't just need to abort on error either. If the command fails I have another (much slower) way to get the data whereas if it succeeds with null output I want to continue on happily. Which means I need exit status. Is this an oversight in the spec?

Thanks,
David Boyce