makefilegnu-make

In gnu make how subst works?

Please explain to me what this line of make does(the subst part)?

TRACK_CFLAGS = $(CC):$(subst ','\'',$(ALL_CFLAGS)):$(USE_GETTEXT_SCHEME)

I think it should replace single quote character with \'.

Solution

  • I think it should replace single quote character with \'.

    This will explain:

    $ cat Makefile
in := 'aa'bb'
out_wrong := $(subst ','\'',$(in))
out_right := $(subst ',\',$(in))
$(info in=[$(in)])
$(info $$(subst ','\'',$$(in)) = [$(out_wrong)] (wrong))
$(info $$(subst ',\',$$(in)) = [$(out_right)] (right))

all:

$ make
in=['aa'bb']
$(subst ','\'',$(in)) = ['\''aa'\''bb'\''] (wrong)
$(subst ',\',$(in)) = [\'aa\'bb\'] (right)
make: Nothing to be done for 'all'.