12.11 Comments in Make Rules

Never put comments in a rule.

Some make treat anything starting with a tab as a command for the current rule, even if the tab is immediately followed by a #. The make from Tru64 Unix V5.1 is one of them. The following makefile runs # foo through the shell.

all:
        # foo

As a workaround, you can use the : no-op command with a string argument that gets ignored:

all:
        : "foo"