# This allows us to work with the newline character: define newline endef newline := $(newline) # nl-escape # # Usage: escape = $(call nl-escape[,escape]) # # This is used as the common way to specify # what should replace a newline when escaping # newlines; the default is a bizarre string. # nl-escape = $(if $(1),$(1),m822df3020w6a44id34bt574ctac44eb9f4n) # escape-nl # # Usage: escaped-text = $(call escape-nl,text[,escape]) # # GNU make's $(shell ...) function converts to a # single space each newline character in the output # produced during the expansion; this may not be # desirable. # # The only solution is to change each newline into # something that won't be converted, so that the # information can be recovered later with # $(call unescape-nl...) # escape-nl = $(subst $(newline),$(call nl-escape,$(2)),$(1)) # unescape-nl # # Usage: text = $(call unescape-nl,escaped-text[,escape]) # # See escape-nl. # unescape-nl = $(subst $(call nl-escape,$(2)),$(newline),$(1)) # shell-escape-nl # # Usage: $(shell some-command | $(call shell-escape-nl[,escape])) # # Use this to escape newlines from within a shell call; # the default escape is a bizarre string. # # NOTE: The escape is used directly as a string constant # in an `awk' program that is delimited by shell # single-quotes, so be wary of the characters # that are chosen. # define shell-escape-nl awk 'NR==1 {t=$$0} NR>1 {t=t "$(nl-escape)" $$0} END {printf t}' endef # shell-unescape-nl # # Usage: $(shell some-command | $(call shell-unescape-nl[,escape])) # # Use this to unescape newlines from within a shell call; # the default escape is a bizarre string. # # NOTE: The escape is used directly as an extended regular # expression constant in an `awk' program that is # delimited by shell single-quotes, so be wary # of the characters that are chosen. # # (The bash shell has a bug where `{gsub(...),...}' is # misinterpreted as a brace expansion; this can be # overcome by putting a space between `{' and `gsub'). # define shell-unescape-nl awk 'NR==1 {t=$$0} NR>1 {t=t "\n" $$0} END { gsub(/$(nl-escape)/,"\n",t); printf t }' endef # escape-for-shell-sq # # Usage: embeddable-text = $(call escape-for-shell-sq,text) # # This function produces text that is suitable for # embedding in a shell string that is delimited by # single-quotes. # escape-for-shell-sq = $(subst ','\'',$(1)) # shell-sq # # Usage: single-quoted-and-escaped-text = $(call shell-sq,text) # shell-sq = '$(escape-for-shell-sq)' # shell-wordify # # Usage: wordified-text = $(call shell-wordify,text) # # For instance: # # |define text # |hello # |world # |endef # | # |target: # | echo $(call shell-wordify,$(text)) # # At least GNU make gets confused by expanding a newline # within the context of a command line of a makefile rule # (this is in constrast to a `$(shell ...)' function call, # which can handle it just fine). # # This function avoids the problem by producing a string # that works as a shell word, regardless of whether or # not it contains a newline. # # If the text to be wordified contains a newline, then # an intrictate shell command substitution is constructed # to render the text as a single line; when the shell # processes the resulting escaped text, it transforms # it into the original unescaped text. # # If the text does not contain a newline, then this function # produces the same results as the `$(shell-sq)' function. # shell-wordify = $(if $(findstring $(newline),$(1)),$(_sw-esc-nl),$(shell-sq)) define _sw-esc-nl "$$(echo $(call escape-nl,$(shell-sq),$(2)) | $(call shell-unescape-nl,$(2)))" endef # is-absolute # # Usage: bool-value = $(call is-absolute,path) # is-absolute = $(shell echo $(shell-sq) | grep -q ^/ && echo y) # lookup # # Usage: absolute-executable-path-or-empty = $(call lookup,path) # # (It's necessary to use `sh -c' because GNU make messes up by # trying too hard and getting things wrong). # lookup = $(call unescape-nl,$(shell sh -c $(_l-sh))) _l-sh = $(call shell-sq,command -v $(shell-sq) | $(call shell-escape-nl,)) # is-executable # # Usage: bool-value = $(call is-executable,path) # # (It's necessary to use `sh -c' because GNU make messes up by # trying too hard and getting things wrong). # is-executable = $(call _is-executable-helper,$(shell-sq)) _is-executable-helper = $(shell sh -c $(_is-executable-sh)) _is-executable-sh = $(call shell-sq,test -f $(1) -a -x $(1) && echo y) # get-executable # # Usage: absolute-executable-path-or-empty = $(call get-executable,path) # # The goal is to get an absolute path for an executable; # the `command -v' is defined by POSIX, but it's not # necessarily very portable, so it's only used if # relative path resolution is requested, as determined # by the presence of a leading `/'. # get-executable = $(if $(1),$(if $(is-absolute),$(_ge-abspath),$(lookup))) _ge-abspath = $(if $(is-executable),$(1)) # get-supplied-or-default-executable # # Usage: absolute-executable-path-or-empty = $(call get-executable-or-default,variable,default) # define get-executable-or-default $(if $($(1)),$(call _ge_attempt,$($(1)),$(1)),$(call _ge_attempt,$(2))) endef _ge_attempt = $(if $(get-executable),$(get-executable),$(call _gea_err,$(2))) _gea_err = $(if $(1),$(error Please set '$(1)' appropriately))