# This allows us to work with the newline character:define newline  endefnewline := $(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-nlawk '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-nlawk '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))