gistfile1.mak

#
# Итак, упрощенный вариант для демонстрации чуда.
#

tmp := $(shell touch a.txt)
srcs := $(wildcard *.txt)

all: $(srcs)
	@echo $(srcs)

clean:
	rm -rf *.txt

.-(~/Documents/projects/make_wtf)----------------------------------------------------------------------------------------------(malkolm@malkolms-MacBook-Air)-
`--> make clean
rm -rf *.txt
.-(~/Documents/projects/make_wtf)----------------------------------------------------------------------------------------------(malkolm@malkolms-MacBook-Air)-
`--> make

.-(~/Documents/projects/make_wtf)----------------------------------------------------------------------------------------------(malkolm@malkolms-MacBook-Air)-
`--> make
a.txt

#
# Поменяем местами, разницы нет.
#

srcs := $(wildcard *.txt)
tmp := $(shell touch a.txt)

all: $(srcs)
	@echo $(srcs)

clean:
	rm -rf *.txt

.-(~/Documents/projects/make_wtf)----------------------------------------------------------------------------------------------(malkolm@malkolms-MacBook-Air)-
`--> make clean
rm -rf *.txt
.-(~/Documents/projects/make_wtf)----------------------------------------------------------------------------------------------(malkolm@malkolms-MacBook-Air)-
`--> make

.-(~/Documents/projects/make_wtf)----------------------------------------------------------------------------------------------(malkolm@malkolms-MacBook-Air)-
`--> make
a.txt

#
# Заменим wildcard на shell, внезапно все работает.
#
tmp := $(shell touch a.txt)
srcs := $(shell echo *.txt)

all: $(srcs)
	@echo $(srcs)

clean:
	rm -rf *.txt

.-(~/Documents/projects/make_wtf)----------------------------------------------------------------------------------------------(malkolm@malkolms-MacBook-Air)-
`--> make clean
rm -rf *.txt
.-(~/Documents/projects/make_wtf)----------------------------------------------------------------------------------------------(malkolm@malkolms-MacBook-Air)-
`--> make
a.txt
.-(~/Documents/projects/make_wtf)----------------------------------------------------------------------------------------------(malkolm@malkolms-MacBook-Air)-
`--> make
a.txt

#
# Банально поменяем порядок, уже не работает.
#
srcs := $(shell echo *.txt)
tmp := $(shell touch a.txt)

all: $(srcs)
	@echo $(srcs)

clean:
	rm -rf *.txt

.-(~/Documents/projects/make_wtf)----------------------------------------------------------------------------------------------(malkolm@malkolms-MacBook-Air)-
`--> make clean
rm -rf *.txt
.-(~/Documents/projects/make_wtf)----------------------------------------------------------------------------------------------(malkolm@malkolms-MacBook-Air)-
`--> make
make: *** No rule to make target `*.txt', needed by `all'.  Stop.
.-(~/Documents/projects/make_wtf)----------------------------------------------------------------------------------------------(malkolm@malkolms-MacBook-Air)-
`--> make
a.txt

#
# Судя по всему shell & wildcard вычисляются на разных стадиях.
#