make always remakes PHONY static rule targets

Question

I've been scratching my head for about an hour now, and Google has proved of limited use. I have a Makefile for a report which contains graphs. The graphs are represented by .plot files inside the directory graphs/, and gnuplot is used to generate .tex and .eps files from them. ps2pdf is then used to generate a pdf from the .eps, and finally an `\include` command inside report.tex includes the graph .tex into the document, which again includes the graph .pdf to put the graph in the final report.pdf. I have a Makefile which builds everything correctly, but for some reason, make insists on remaking report.pdf every time I run make. A read through the ouput of `make -d` reveals that Make says: "Must remake target `mp-int-2.4-ni'." and "Must remake target`mp-int-2.4-i'." every run, but these are declared as PHONY, and thus shouldn't be remade unless something they depend on has change. Or at least so I thought? Any thoughts on what might be causing this and how I might avoid having to rem…

Accepted Answer

A PHONY rule is one that you have told make doesn't correspond to an actual file so it isn't checking for the files to exist and so it always assumes the rule needs to run and so report.pdf has prerequisites that are newer (which is what that output is telling you).

The make documentation says "A phony target should not be a prerequisite of a real target file; if it is, its recipe will be run every time make goes to update that file." [ref]

What was your purpose in marking those files as PHONY?

make always remakes PHONY static rule targets

Solution

Problem