# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1488115776 -3600
# Node ID 67f2da40bb32603dc0e9eafd47a1d107f54e4d30
# Parent  00ee53b9977bb80c774de54cc847e9f25836a755
Added constant identifier digest collision testing.

diff -r 00ee53b9977b -r 67f2da40bb32 errors.py
--- a/errors.py	Sun Feb 26 00:11:12 2017 +0100
+++ b/errors.py	Sun Feb 26 14:29:36 2017 +0100
@@ -4,7 +4,7 @@
 Error classes.
 
 Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012
-              2014, 2016 Paul Boddie <paul@boddie.org.uk>
+              2014, 2016, 2017 Paul Boddie <paul@boddie.org.uk>
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -85,6 +85,13 @@
     def __str__(self):
         return "Error in deduction: %s" % self.message
 
+class OptimiseError(ProgramError):
+
+    "An error during optimisation."
+
+    def __str__(self):
+        return "Error in optimisation: %s" % self.message
+
 class TranslateError(NodeProcessingError):
 
     "An error during the module translation process."
diff -r 00ee53b9977b -r 67f2da40bb32 optimiser.py
--- a/optimiser.py	Sun Feb 26 00:11:12 2017 +0100
+++ b/optimiser.py	Sun Feb 26 14:29:36 2017 +0100
@@ -22,6 +22,7 @@
 from common import add_counter_item, get_attrname_from_location, init_item, \
                    sorted_output
 from encoders import digest, encode_access_location, encode_instruction, get_kinds
+from errors import OptimiseError
 from os.path import exists, join
 from os import makedirs
 from referencing import Reference
@@ -73,6 +74,7 @@
 
         self.constants = []
         self.constant_numbers = {}
+        self.digests = {}
 
         # Optimiser activities.
 
@@ -742,7 +744,21 @@
             # Each constant is actually (value, value_type, encoding).
 
             for constant, n in constants.items():
-                self.constants[constant] = digest(constant)
+                d = digest(constant)
+                self.constants[constant] = d
+
+                # Make sure the digests are really distinct for different
+                # constants.
+
+                if self.digests.has_key(d):
+                    if self.digests[d] != constant:
+                        raise OptimiseError, "Digest %s used for distinct constants %r and %r." % (
+                                             d, self.digests[d], constant)
+                else:
+                    self.digests[d] = constant
+
+        # Establish a mapping from local constant identifiers to consolidated
+        # constant identifiers.
 
         self.constant_numbers = {}