Using Make $(dir) or $(notdir) on a path with spaces

Question

I'm using code similar to the following in a Makefile:

empty:=
space:= $(empty) $(empty)
path_escape = $(subst $(space),\$(space),$(1))

TOP=$(call path_escape,$(abspath .))
TARGET=$(TOP)/foo

$(info TOP='$(TOP)')
$(info TARGET='$(TARGET)')

all: $(TARGET)

$(TARGET):
    touch '$(notdir $@)'

.PHONY: $(TARGET)

If I use this in a directory with no spaces, say space-test, it works fine:

$ make
TOP='/tmp/space-test'
TARGET='/tmp/space-test/foo'
touch 'foo'

However, if I use it in a directory with spaces, say space test, then $(notdir) does the wrong thing:

TOP='/tmp/space\ test'
TARGET='/tmp/space\ test/foo'
touch 'space foo'

What's happening here is that $(notdir) interprets /tmp/space test/foo as two paths and returns the "file part" of both (i.e., space and foo). The weird part of this is that TARGET is properly escaped; somehow, inside the rule or inside $(notdir), the backslash escapes are being ignored.

What am I doing wrong here?

Answer 1

The $(notdir) function in GNU Make takes a list of arguments, separated by spaces. Some functions support escaping spaces with \\, but $(notdir) is not one of them.

This should work:

s? = $(subst $(empty) ,?,$1)
?s = $(subst ?, ,$1)
notdirx = $(call ?s,$(notdir $(call s?,$1)))

$(TARGET):
    touch '$(call notdirx,$@)'

This defines a "space-safe" version of notdir called notdirx. It's quite simple: s? first turns all spaces to question marks (hoping that they cannot be present in file names), and ?s converts back. In between we can safely call the original notdir function.

For an excellent summary on GNU Make and spaces in file names, see GNU Make meets file names with spaces in them.