From 55331e9c5407cd22e858ed325a38dd85dadb9c31 Mon Sep 17 00:00:00 2001
From: Chris Pressey <cpressey@catseye.tc>
Date: Fri, 9 Feb 2018 13:35:59 +0000
Subject: [PATCH] Statics are always writeable. Statics are always meaningful.

---
 src/sixtypical/analyzer.py   | 14 +++++++++++++-
 src/sixtypical/model.py      |  2 +-
 src/sixtypical/parser.py     | 19 +++++++++++++------
 tests/SixtyPical Analysis.md | 26 ++++++++++++++++++++++++++
 4 files changed, 53 insertions(+), 8 deletions(-)

diff --git a/src/sixtypical/analyzer.py b/src/sixtypical/analyzer.py
index b63ff59..74466f4 100644
--- a/src/sixtypical/analyzer.py
+++ b/src/sixtypical/analyzer.py
@@ -53,6 +53,12 @@ class IncompatibleConstraintsError(ConstraintsError):
     pass
 
 
+def routine_has_static(routine, ref):
+    if not hasattr(routine, 'statics'):
+        return False
+    return ref in [static.location for static in routine.statics]
+
+
 class Context(object):
     """
     A location is touched if it was changed (or even potentially
@@ -112,6 +118,9 @@ class Context(object):
     def assert_meaningful(self, *refs, **kwargs):
         exception_class = kwargs.get('exception_class', UnmeaningfulReadError)
         for ref in refs:
+            # statics are always meaningful
+            if routine_has_static(self.routine, ref):
+                continue
             if ref.is_constant() or ref in self.routines:
                 pass
             elif isinstance(ref, LocationRef):
@@ -129,6 +138,9 @@ class Context(object):
     def assert_writeable(self, *refs, **kwargs):
         exception_class = kwargs.get('exception_class', ForbiddenWriteError)
         for ref in refs:
+            # statics are always writeable
+            if routine_has_static(self.routine, ref):
+                continue
             if ref not in self._writeable:
                 message = '%s in %s' % (ref.name, self.routine.name)
                 if kwargs.get('message'):
@@ -231,7 +243,7 @@ class Analyzer(object):
             for ref in type_.outputs:
                 context.assert_meaningful(ref, exception_class=UnmeaningfulOutputError)
             for ref in context.each_touched():
-                if ref not in type_.outputs and ref not in type_.trashes:
+                if ref not in type_.outputs and ref not in type_.trashes and not routine_has_static(routine, ref):
                     message = '%s in %s' % (ref.name, routine.name)
                     raise ForbiddenWriteError(message)
         self.current_routine = None
diff --git a/src/sixtypical/model.py b/src/sixtypical/model.py
index 64e9880..3cc7f94 100644
--- a/src/sixtypical/model.py
+++ b/src/sixtypical/model.py
@@ -145,7 +145,7 @@ class LocationRef(Ref):
         # just to be sure.
         equal = isinstance(other, self.__class__) and other.name == self.name
         if equal:
-            assert other.type == self.type
+            assert other.type == self.type, repr((self, other))
         return equal
 
     def __hash__(self):
diff --git a/src/sixtypical/parser.py b/src/sixtypical/parser.py
index 4da156c..f9423de 100644
--- a/src/sixtypical/parser.py
+++ b/src/sixtypical/parser.py
@@ -14,6 +14,9 @@ class SymEntry(object):
         self.ast_node = ast_node
         self.model = model
 
+    def __repr__(self):
+        return "%s(%r, %r)" % (self.__class__.__name__, self.ast_node, self.model)
+
 
 class Parser(object):
     def __init__(self, text):
@@ -221,12 +224,7 @@ class Parser(object):
         else:
             statics = self.statics()
 
-            self.current_statics = {}
-            for defn in statics:
-                name = defn.name
-                if name in self.symbols or name in self.current_statics:
-                    raise SyntaxError('Symbol "%s" already declared' % name)
-                self.current_statics[name] = SymEntry(defn, defn.location)
+            self.current_statics = self.compose_statics_dict(statics)
             block = self.block()
             self.current_statics = {}
 
@@ -237,6 +235,15 @@ class Parser(object):
             location=location, statics=statics
         )
 
+    def compose_statics_dict(self, statics):
+        c = {}
+        for defn in statics:
+            name = defn.name
+            if name in self.symbols or name in self.current_statics:
+                raise SyntaxError('Symbol "%s" already declared' % name)
+            c[name] = SymEntry(defn, defn.location)
+        return c
+
     def labels(self):
         accum = []
         accum.append(self.label())
diff --git a/tests/SixtyPical Analysis.md b/tests/SixtyPical Analysis.md
index 641628a..05c556f 100644
--- a/tests/SixtyPical Analysis.md	
+++ b/tests/SixtyPical Analysis.md	
@@ -2283,3 +2283,29 @@ The new style routine definitions support typedefs.
     |     copy foo, vec
     | }
     = ok
+
+### static ###
+
+When memory locations are defined static to a routine, they cannot be
+directly input, nor directly output; and since they are always initialized,
+they cannot be trashed.  Thus, they really don't participate in the analysis.
+
+    | define foo routine
+    |   inputs x
+    |   outputs x
+    |   trashes z, n
+    |   static byte t : 0
+    | {
+    |   st x, t
+    |   inc t
+    |   ld x, t
+    | }
+    | 
+    | define main routine
+    |   trashes a, x, z, n
+    |   static byte t : 0
+    | {
+    |   ld x, t
+    |   call foo
+    | }
+    = ok