how to identify the prerequisite causing the build?

[Martin d'Anjou]

Hi,

I run make with -d, but there are thousands and thousands of lines... I 
am not expecting a re-build, but make thinks a rebuilt is in order. The 
problem is that I cannot find why make thinks this is the right thing to 
do. Based on what make wants to build, no prerequisite is missing, but 
how do I get make to tell me exactly the chain of prerequisites that 
causes the rebuild?

I do not find a "File does not exist" message, or a missing 
prerequisite, all I see is "Prerequisite is older than target". What 
should I look for?

Thanks,
Martin