From b9d89b95bbb1a89842cd9a285390a265157c6779 Mon Sep 17 00:00:00 2001
From: Björn Persson <Bjorn@Rombobjörn.se>
Date: Sun, 23 Feb 2014 15:26:27 +0100
Subject: Improved the error when an option is undefined.

---
 comfignat.mk | 41 +++++++++++++++++++++++------------------
 1 file changed, 23 insertions(+), 18 deletions(-)

diff --git a/comfignat.mk b/comfignat.mk
index bfe60ba..be030f0 100644
--- a/comfignat.mk
+++ b/comfignat.mk
@@ -424,21 +424,28 @@ usage_relevant = ${filter ${usage_directory_variables},${1}}
 # relevant directory variables. If given a single variable name, it returns
 # that name if the variable is usage-relevant, or an empty string if it isn't.
 
-maybe_relative_to = \
-   ${if ${or ${filter-out 1,${words ${relocatable_package}}}, \
-             ${filter-out true false,${relocatable_package}}}, \
-        ${error relocatable_package must be "true" or "false"} \
-       ,${if ${filter true,${relocatable_package}} \
-            ,${call relative_to,${1},${2}},${1}}}
+checked_boolean = ${or ${and ${filter 1,${words ${${1}}}}, \
+                             ${filter true false,${${1}}}}, \
+                       ${error ${1} must be "true" or "false"}}
+# checked_boolean takes the name of a variable and checks that its value is a
+# single word, and that that word is either "true" or "false". If so it returns
+# the value; otherwise it complains and stops the execution.
+
+checked_true = ${filter true,${call checked_boolean,${1}}}
+# checked_true takes the name of a variable and checks that it has a boolean
+# value. It then returns an empty string for "false" or a non-empty string for
+# "true".
+
+maybe_relative_to = ${if ${call checked_true,relocatable_package} \
+                        ,${call relative_to,${1},${2}},${1}}
 # maybe_relative_to converts an absolute pathname into a relative one if a
 # relocatable package is desired.
 # Parameters:
 #    1: an absolute pathname to maybe convert to relative
 #    2: the absolute base pathname that 1 may be made relative to
-# First check that the value of relocatable_package is a single word and that
-# that word is either "true" or "false". Complain and stop if that isn't so.
-# Then, if relocatable_package is "true", let relative_to convert the pathname,
+# If relocatable_package is "true", then let relative_to convert the pathname,
 # otherwise return parameter 1 unchanged.
+# It is checked that relocatable_package has a boolean value.
 
 embed_pathname = ${call maybe_relative_to,${${1}},${if ${filter bindir,${1}} \
                                                       ,${libexecdir},${bindir}}}
@@ -541,15 +548,13 @@ ${eval ${foreach var,${builder_directory_variables}, \
 
 option_values = \
    ${foreach option,${options}, \
-             ${if ${and ${filter-out environment,${origin ${option}}}, \
-                        ${filter 1,${words ${${option}}}}, \
-                        ${filter true false,${${option}}}}, \
-                  ${option}=${${option}}, \
-                  ${error ${option} must be "true" or "false"}}}
-# For each variable listed in options, check that it didn't come from the
-# environment (to prevent accidents), that its value is a single word, and that
-# that word is either "true" or "false". If so, output a name/value pair;
-# otherwise complain and stop.
+             ${if ${filter-out undefined environment,${origin ${option}}}, \
+                  ${option}=${call checked_boolean,${option}}, \
+                  ${error ${option} has no default value and must be set to \
+                          "true" or "false" on the command line}}}
+# For each variable listed in options, check that it exists, that it didn't
+# come from the environment (to prevent accidents), and that it has a boolean
+# value. If so, output a name/value pair; otherwise complain and stop.
 
 # Convey boolean options to Gnatprep.
 options_preprocessing = ${addprefix -D,${option_values}}
-- 
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