Experimenting with compiler introspection in GNU Make

Makefile.gnu23

.PHONY: default gnu23 gnu23.mk
default:| gnu23; $(info $(CC) -std=$(gnu23))
gnu23:| gnu23.mk; $(eval include gnu23.mk)
gnu23.mk: gnu23.h; @$(CC) -E -xc -P $< >$@
gnu23.h: $(lastword $(MAKEFILE_LIST)); $(call cstd,$@) @:
override cstd =$(file >$1,$(.cstd))
override .cstd              =$(call \
P,#ifdef __clang_major__)    $(call \
L,#if __clang_major__ > 17)  $(call \
L,override gnu23 := gnu23)   $(call \
L,#elif __clang_major__ > 8) $(call \
L,override gnu23 := gnu2x)   $(call \
L,#endif)                    $(call \
L,#elif __GNUC__ > 13)       $(call \
L,override gnu23 := gnu23)   $(call \
L,#elif __GNUC__ > 8)        $(call \
L,override gnu23 := gnu2x)   $(call \
L,#endif)
override  P = $(call .P,$(value 1))
override .P = $(value 1)
override  L = $(call .L,$(value 1))
override .L = $n$(value 1)
override define n:=


endef