From b1b84a123eeb90ab9d0f0e87bafb5223ecd15077 Mon Sep 17 00:00:00 2001
From: Sei Lisa <sei-lisa@email.fake>
Date: Fri, 6 May 2016 20:15:46 +0200
Subject: [PATCH] Add broken FS switch behaviour for compatibility.

In the absence of a 'default' label within a switch, FS falls through to the first CASE label (or to the code before the first CASE if there's any).

This commit adds an option, active by default for FS compatibility, that mimics this broken behaviour, as well as a warning in case the 'default' label is absent, which also triggers another warning when the option is active.
---
 lslopt/lslparse.py | 16 ++++++++++++----
 main.py            |  7 ++++++-
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/lslopt/lslparse.py b/lslopt/lslparse.py
index 79caf74..f4acebf 100644
--- a/lslopt/lslparse.py
+++ b/lslopt/lslparse.py
@@ -1674,10 +1674,15 @@ list lazy_list_set(list L, integer i, list v)
                     ]})
 
             if switchcasedefault is None:
-                switchcasedefault = brk
-                self.breakstack[-1][2] = True
-            prelude.append({'nt':'JUMP', 't':None, 'name':switchcasedefault,
-                'scope':blkscope})
+                warning("No 'default:' label in switch statement")
+                if self.brokennodefault:
+                    warning("Broken behaviour active - falling through")
+                if not self.brokennodefault:
+                    switchcasedefault = brk
+                    self.breakstack[-1][2] = True
+            if switchcasedefault is not None:
+                prelude.append({'nt':'JUMP', 't':None, 'name':switchcasedefault,
+                    'scope':blkscope})
             last = self.breakstack.pop()
             if last[2]:
                 blk.append({'nt':'@', 'name':brk, 'scope':blkscope})
@@ -2311,6 +2316,9 @@ list lazy_list_set(list L, integer i, list v)
         if self.enableswitch:
             self.keywords |= frozenset(('switch', 'case', 'break'))
 
+        # Broken behaviour in the absence of a default: label in a switch stmt.
+        self.brokennodefault = 'brokennodefault' in options
+
         # Allow brackets for assignment of list elements e.g. mylist[5]=4
         self.lazylists = 'lazylists' in options
 
diff --git a/main.py b/main.py
index c1ba024..88deec2 100755
--- a/main.py
+++ b/main.py
@@ -228,6 +228,11 @@ Optimizer options (+ means active by default, - means inactive by default):
                        will go to the last label with that name). This flag
                        works around that limitation by replacing the names of
                        the labels in the output with unique ones.
+  brokennodefault    + Mimic Firestorm's legacy broken behaviour when the
+                       'default' label in a switch statement is absent. Rather
+                       than jumping to the end of the switch in that case
+                       (which is how it behaves when this option is not set),
+                       it falls through and executes the first 'case' label.
 
   Deprecated / compatibility syntax extensions options:
 
@@ -300,7 +305,7 @@ def main():
     # Default options
     options = set(('extendedglobalexpr','extendedtypecast','extendedassignment',
         'allowkeyconcat','allowmultistrings','skippreproc','optimize',
-        'optsigns','optfloats','constfold','dcr'
+        'optsigns','optfloats','constfold','dcr', 'brokennodefault',
         ))
 
     try: