Question

Question 1
If you define step

  22 clean:
  23   rm $(OBJECTS)

If there any way to gracefully “do nothing, if there is nothing to delete“?

Question 2
Assume the following line, again, is there a way to gracefully exit with a warhing when no files are found when processing line

  6 SOURCES = $(shell echo src/*.cpp)

Question 3
How can one perform the final post processing on the final product, like mv $(PRODUCT) someDir? Where would this instruction be?

Answer 1

1) Just use rm -f, which is telling rm to ignore it if the files are missing.

3) That can just be the last step of the target that actually builds the product, or you can create a target named install (for example) that depends on your build target, and then contains this mv command.