Debugging GNU make

Question

Is there a command line way in make to find out which of the prerequisites of a target is not updated?

Answer 1

What I usually do is not go using -d as previous answerers said.

I either:

1. Use -p to print the database, to see what rules have been created. This is handy if you have second expansion rules and are creating rules on the fly, especially recursive make.
2. Heavy use of $(info) function.
3. Use the tips and trick described in this DrDobbs article Debugging Makefiles

Below is some code I'm using for printing out values:

define pv
$(info $(1) [$(origin $(1))] : >|$($(1))|<)
endef

define pva
$(foreach t,$(1),$(call pv,$(t)))
endef

define itemizer
$(foreach t,$($(1)),$(info $(t)))
endef