Recent-ish versions of make do no longer consider number signs ("#") as comment symbols when they are inserted inside of a macro reference or in a function invocation. In such cases, the symbols should not be escaped. There are a few occurrences of "\#" in libbpf's and samples' Makefiles. In the former, the backslash is harmless, because grep associates no particular meaning to the escaped symbol and reads it as a regular "#". In samples' Makefile, recent versions of make will pass the backslash down to the compiler, making the probe fail all the time and resulting in the display of a warning about "make headers_install" being required, even after headers have been installed. A similar issue has been addressed at some other locations by commit 9564a8cf422d ("Kbuild: fix # escaping in .cmd files for future Make"). Let's address it for libbpf's and samples' Makefiles in the same fashion, by using a "$(pound)" variable (pulled from tools/scripts/Makefile.include for libbpf, or re-defined for the samples). Reference for the change in make: https://git.savannah.gnu.org/cgit/make.git/commit/?id=c6966b323811c37acedff05b57 Fixes: 2f3830412786 ("libbpf: Make libbpf_version.h non-auto-generated") Fixes: 07c3bbdb1a9b ("samples: bpf: print a warning about headers_install") Signed-off-by: Quentin Monnet <quentin@isovalent.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20211006111049.20708-1-quentin@isovalent.com