makefile unexpectedly removes target

Question

A minimal example:

%.txt: foo.log
    # pass

%.log:
    # pass

Run:

$ make a.txt --dry-run
# pass
# pass
rm foo.log

Why is the last action rm foo.log? How can I get rid of it?

Answer 1

By default, GNU make removes intermediate files. Since %.txt depends on %.log, make wants to remove the .log file. To prevent that behavior you mark them as precious with .PRECIOUS or .SECONDARY.

.PRECIOUS: foo.log

Also, you can make it so that no intermediate files are ever removed by using .SECONDARY with no dependencies.

.SECONDARY:

See this section of the GNU make manual.