tools/scripts/utilities.mak

   1 # This allows us to work with the newline character:
   2 define newline
   3
   4
   5 endef
   6 newline := $(newline)
   7
   8 # nl-escape
   9 #
  10 # Usage: escape = $(call nl-escape[,escape])
  11 #
  12 # This is used as the common way to specify
  13 # what should replace a newline when escaping
  14 # newlines; the default is a bizarre string.
  15 #
  16 nl-escape = $(if $(1),$(1),m822df3020w6a44id34bt574ctac44eb9f4n)
  17
  18 # escape-nl
  19 #
  20 # Usage: escaped-text = $(call escape-nl,text[,escape])
  21 #
  22 # GNU make's $(shell ...) function converts to a
  23 # single space each newline character in the output
  24 # produced during the expansion; this may not be
  25 # desirable.
  26 #
  27 # The only solution is to change each newline into
  28 # something that won't be converted, so that the
  29 # information can be recovered later with
  30 # $(call unescape-nl...)
  31 #
  32 escape-nl = $(subst $(newline),$(call nl-escape,$(2)),$(1))
  33
  34 # unescape-nl
  35 #
  36 # Usage: text = $(call unescape-nl,escaped-text[,escape])
  37 #
  38 # See escape-nl.
  39 #
  40 unescape-nl = $(subst $(call nl-escape,$(2)),$(newline),$(1))
  41
  42 # shell-escape-nl
  43 #
  44 # Usage: $(shell some-command | $(call shell-escape-nl[,escape]))
  45 #
  46 # Use this to escape newlines from within a shell call;
  47 # the default escape is a bizarre string.
  48 #
  49 # NOTE: The escape is used directly as a string constant
  50 #       in an `awk' program that is delimited by shell
  51 #       single-quotes, so be wary of the characters
  52 #       that are chosen.
  53 #
  54 define shell-escape-nl
  55 awk 'NR==1 {t=$$0} NR>1 {t=t "$(nl-escape)" $$0} END {printf t}'
  56 endef
  57
  58 # shell-unescape-nl
  59 #
  60 # Usage: $(shell some-command | $(call shell-unescape-nl[,escape]))
  61 #
  62 # Use this to unescape newlines from within a shell call;
  63 # the default escape is a bizarre string.
  64 #
  65 # NOTE: The escape is used directly as an extended regular
  66 #       expression constant in an `awk' program that is
  67 #       delimited by shell single-quotes, so be wary
  68 #       of the characters that are chosen.
  69 #
  70 # (The bash shell has a bug where `{gsub(...),...}' is
  71 #  misinterpreted as a brace expansion; this can be
  72 #  overcome by putting a space between `{' and `gsub').
  73 #
  74 define shell-unescape-nl
  75 awk 'NR==1 {t=$$0} NR>1 {t=t "\n" $$0} END { gsub(/$(nl-escape)/,"\n",t); printf t }'
  76 endef
  77
  78 # escape-for-shell-sq
  79 #
  80 # Usage: embeddable-text = $(call escape-for-shell-sq,text)
  81 #
  82 # This function produces text that is suitable for
  83 # embedding in a shell string that is delimited by
  84 # single-quotes.
  85 #
  86 escape-for-shell-sq =  $(subst ','\'',$(1))
  87
  88 # shell-sq
  89 #
  90 # Usage: single-quoted-and-escaped-text = $(call shell-sq,text)
  91 #
  92 shell-sq = '$(escape-for-shell-sq)'
  93
  94 # shell-wordify
  95 #
  96 # Usage: wordified-text = $(call shell-wordify,text)
  97 #
  98 # For instance:
  99 #
 100 #  |define text
 101 #  |hello
 102 #  |world
 103 #  |endef
 104 #  |
 105 #  |target:
 106 #  |    echo $(call shell-wordify,$(text))
 107 #
 108 # At least GNU make gets confused by expanding a newline
 109 # within the context of a command line of a makefile rule
 110 # (this is in constrast to a `$(shell ...)' function call,
 111 # which can handle it just fine).
 112 #
 113 # This function avoids the problem by producing a string
 114 # that works as a shell word, regardless of whether or
 115 # not it contains a newline.
 116 #
 117 # If the text to be wordified contains a newline, then
 118 # an intrictate shell command substitution is constructed
 119 # to render the text as a single line; when the shell
 120 # processes the resulting escaped text, it transforms
 121 # it into the original unescaped text.
 122 #
 123 # If the text does not contain a newline, then this function
 124 # produces the same results as the `$(shell-sq)' function.
 125 #
 126 shell-wordify = $(if $(findstring $(newline),$(1)),$(_sw-esc-nl),$(shell-sq))
 127 define _sw-esc-nl
 128 "$$(echo $(call escape-nl,$(shell-sq),$(2)) | $(call shell-unescape-nl,$(2)))"
 129 endef
 130
 131 # is-absolute
 132 #
 133 # Usage: bool-value = $(call is-absolute,path)
 134 #
 135 is-absolute = $(shell echo $(shell-sq) | grep -q ^/ && echo y)
 136
 137 # lookup
 138 #
 139 # Usage: absolute-executable-path-or-empty = $(call lookup,path)
 140 #
 141 # (It's necessary to use `sh -c' because GNU make messes up by
 142 #  trying too hard and getting things wrong).
 143 #
 144 lookup = $(call unescape-nl,$(shell sh -c $(_l-sh)))
 145 _l-sh = $(call shell-sq,command -v $(shell-sq) | $(call shell-escape-nl,))
 146
 147 # is-executable
 148 #
 149 # Usage: bool-value = $(call is-executable,path)
 150 #
 151 # (It's necessary to use `sh -c' because GNU make messes up by
 152 #  trying too hard and getting things wrong).
 153 #
 154 is-executable = $(call _is-executable-helper,$(shell-sq))
 155 _is-executable-helper = $(shell sh -c $(_is-executable-sh))
 156 _is-executable-sh = $(call shell-sq,test -f $(1) -a -x $(1) && echo y)
 157
 158 # get-executable
 159 #
 160 # Usage: absolute-executable-path-or-empty = $(call get-executable,path)
 161 #
 162 # The goal is to get an absolute path for an executable;
 163 # the `command -v' is defined by POSIX, but it's not
 164 # necessarily very portable, so it's only used if
 165 # relative path resolution is requested, as determined
 166 # by the presence of a leading `/'.
 167 #
 168 get-executable = $(if $(1),$(if $(is-absolute),$(_ge-abspath),$(lookup)))
 169 _ge-abspath = $(if $(is-executable),$(1))
 170
 171 # get-supplied-or-default-executable
 172 #
 173 # Usage: absolute-executable-path-or-empty = $(call get-executable-or-default,variable,default)
 174 #
 175 define get-executable-or-default
 176 $(if $($(1)),$(call _ge_attempt,$($(1)),$(1)),$(call _ge_attempt,$(2)))
 177 endef
 178 _ge_attempt = $(if $(get-executable),$(get-executable),$(call _gea_err,$(2)))
 179 _gea_err  = $(if $(1),$(error Please set '$(1)' appropriately))