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+# config/general.m4
+
+# This file defines new macros to process configure command line
+# arguments, to replace the brain-dead AC_ARG_WITH and AC_ARG_ENABLE.
+# The flaw in these is particularly that they only differentiate
+# between "given" and "not given" and do not provide enough help to
+# process arguments that only accept "yes/no", that require an
+# argument (other than "yes/no"), etc.
+#
+# The point of this implementation is to reduce code size and
+# redundancy in configure.ac and to improve robustness and consistency
+# in the option evaluation code.
+
+
+# Convert type and name to shell variable name (e.g., "enable_long_strings")
+m4_define([pgac_arg_to_variable],
+ [$1[]_[]patsubst($2, -, _)])
+
+
+# PGAC_ARG(TYPE, NAME, HELP-STRING-LHS-EXTRA, HELP-STRING-RHS,
+# [ACTION-IF-YES], [ACTION-IF-NO], [ACTION-IF-ARG],
+# [ACTION-IF-OMITTED])
+# ------------------------------------------------------------
+# This is the base layer. TYPE is either "with" or "enable", depending
+# on what you like. NAME is the rest of the option name.
+# HELP-STRING-LHS-EXTRA is a string to append to the option name on
+# the left-hand side of the help output, e.g., an argument name. If
+# set to "-", append nothing, but let the option appear in the
+# negative form (disable/without). HELP-STRING-RHS is the option
+# description, for the right-hand side of the help output.
+# ACTION-IF-YES is executed if the option is given without an argument
+# (or "yes", which is the same); similar for ACTION-IF-NO.
+
+AC_DEFUN([PGAC_ARG],
+[
+m4_case([$1],
+
+enable, [
+AC_ARG_ENABLE([$2], [AS_HELP_STRING([--]m4_if($3, -, disable, enable)[-$2]m4_if($3, -, , $3), [$4])], [
+ case [$]enableval in
+ yes)
+ m4_default([$5], :)
+ ;;
+ no)
+ m4_default([$6], :)
+ ;;
+ *)
+ $7
+ ;;
+ esac
+],
+[$8])[]dnl AC_ARG_ENABLE
+],
+
+with, [
+AC_ARG_WITH([$2], [AS_HELP_STRING([--]m4_if($3, -, without, with)[-$2]m4_if($3, -, , $3), [$4])], [
+ case [$]withval in
+ yes)
+ m4_default([$5], :)
+ ;;
+ no)
+ m4_default([$6], :)
+ ;;
+ *)
+ $7
+ ;;
+ esac
+],
+[$8])[]dnl AC_ARG_WITH
+],
+
+[m4_fatal([first argument of $0 must be 'enable' or 'with', not '$1'])]
+)
+])# PGAC_ARG
+
+
+# PGAC_ARG_BOOL(TYPE, NAME, DEFAULT, HELP-STRING-RHS,
+# [ACTION-IF-YES], [ACTION-IF-NO])
+# ---------------------------------------------------
+# Accept a boolean option, that is, one that only takes yes or no.
+# ("no" is equivalent to "disable" or "without"). DEFAULT is what
+# should be done if the option is omitted; it should be "yes" or "no".
+# (Consequently, one of ACTION-IF-YES and ACTION-IF-NO will always
+# execute.)
+
+AC_DEFUN([PGAC_ARG_BOOL],
+[dnl The following hack is necessary because in a few instances this
+dnl macro is called twice for the same option with different default
+dnl values. But we only want it to appear once in the help. We achieve
+dnl that by making the help string look the same, which is why we need to
+dnl save the default that was passed in previously.
+m4_define([_pgac_helpdefault], m4_ifdef([pgac_defined_$1_$2_bool], [m4_defn([pgac_defined_$1_$2_bool])], [$3]))dnl
+PGAC_ARG([$1], [$2], [m4_if(_pgac_helpdefault, yes, -)], [$4], [$5], [$6],
+ [AC_MSG_ERROR([no argument expected for --$1-$2 option])],
+ [m4_case([$3],
+ yes, [pgac_arg_to_variable([$1], [$2])=yes
+$5],
+ no, [pgac_arg_to_variable([$1], [$2])=no
+$6],
+ [m4_fatal([third argument of $0 must be 'yes' or 'no', not '$3'])])])[]dnl
+m4_define([pgac_defined_$1_$2_bool], [$3])dnl
+])# PGAC_ARG_BOOL
+
+
+# PGAC_ARG_REQ(TYPE, NAME, HELP-ARGNAME, HELP-STRING-RHS,
+# [ACTION-IF-GIVEN], [ACTION-IF-NOT-GIVEN])
+# -------------------------------------------------------
+# This option will require an argument; "yes" or "no" will not be
+# accepted. HELP-ARGNAME is a name for the argument for the help output.
+
+AC_DEFUN([PGAC_ARG_REQ],
+[PGAC_ARG([$1], [$2], [=$3], [$4],
+ [AC_MSG_ERROR([argument required for --$1-$2 option])],
+ [AC_MSG_ERROR([argument required for --$1-$2 option])],
+ [$5],
+ [$6])])# PGAC_ARG_REQ
+
+
+# PGAC_ARG_OPTARG(TYPE, NAME, HELP-ARGNAME, HELP-STRING-RHS,
+# [DEFAULT-ACTION], [ARG-ACTION],
+# [ACTION-ENABLED], [ACTION-DISABLED])
+# ----------------------------------------------------------
+# This will create an option that behaves as follows: If omitted, or
+# called with "no", then set the enable_variable to "no" and do
+# nothing else. If called with "yes", then execute DEFAULT-ACTION. If
+# called with argument, set enable_variable to "yes" and execute
+# ARG-ACTION. Additionally, execute ACTION-ENABLED if we ended up with
+# "yes" either way, else ACTION-DISABLED.
+#
+# The intent is to allow enabling a feature, and optionally pass an
+# additional piece of information.
+
+AC_DEFUN([PGAC_ARG_OPTARG],
+[PGAC_ARG([$1], [$2], [@<:@=$3@:>@], [$4], [$5], [],
+ [pgac_arg_to_variable([$1], [$2])=yes
+$6],
+ [pgac_arg_to_variable([$1], [$2])=no])
+dnl Add this code only if there's a ACTION-ENABLED or ACTION-DISABLED.
+m4_ifval([$7[]$8],
+[
+if test "[$]pgac_arg_to_variable([$1], [$2])" = yes; then
+ m4_default([$7], :)
+m4_ifval([$8],
+[else
+ $8
+])[]dnl
+fi
+])[]dnl
+])# PGAC_ARG_OPTARG