In ffmpeg Makefile,
https://github.com/FFmpeg/FFmpeg/blob/master/Makefile#L37
https://github.com/FFmpeg/FFmpeg/blob/master/Makefile#L189
It defined phony targets "all" and "all-yes", but I can't find prerequisites and command of "all-yes" by searching whole ffmpeg directory. So can anyone help to explain what "all-yes" exactly means?
There is another "all" target in the "include $(SRC_PATH)/fftools/Makefile": https://github.com/FFmpeg/FFmpeg/blob/master/fftools/Makefile#L30
$(foreach P,$(AVPROGS-yes),$(eval $(call DOFFTOOL,$(P))))
all: $(AVPROGS)
fftools/ffprobe.o fftools/cmdutils.o: libavutil/ffversion.h | fftools
OUTDIRS += fftools
4.11 Multiple Rules for One Target
There can only be one recipe to be executed for a file. If more than one rule gives a recipe for the same file, make uses the last one given and prints an error message. (As a special case, if the file’s name begins with a dot, no error message is printed. This odd behavior is only for compatibility with other implementations of make… you should avoid using it). Occasionally it is useful to have the same target invoke multiple recipes which are defined in different parts of your makefile; you can use double-colon rules (see Double-Colon) for this.
There are two targets and make only uses the last one, so you could delete the "all-yes" or delete "all:all-yes" then use "make all" command, and it has no effect on the compilation. the command line "all:all-yes" is just ensure the "all" is the default target.