From 0180cae8c3f60cce6b518b25238ffd6480373104 Mon Sep 17 00:00:00 2001
From: andy <andy>
Date: Fri, 26 Sep 2008 19:18:19 +0000
Subject: [PATCH] Fix parsing for degenerate cases like a[,] a[:] and {:}.  The
 slicing syntax exposed the low-level generators to some new cases.

---
 simgear/nasal/code.c    | 9 +++++----
 simgear/nasal/codegen.c | 7 ++++---
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/simgear/nasal/code.c b/simgear/nasal/code.c
index 44ff2a0e..11754b20 100644
--- a/simgear/nasal/code.c
+++ b/simgear/nasal/code.c
@@ -491,11 +491,12 @@ static void evalUnpack(naContext ctx, int count)
 // FIXME: unify with almost identical checkVec() above
 static int vbound(naContext ctx, naRef v, naRef ir, int end)
 {
-    int i = IS_NIL(ir) ? (end ? -1 : 0) : numify(ctx, ir);
-    if(i < 0) i += naVec_size(v);
-    if(i < 0 || i >= naVec_size(v))
+    int sz=naVec_size(v), i = IS_NIL(ir) ? (end ? -1 : 0) : numify(ctx, ir);
+    if(IS_NIL(ir) && !sz) return i;
+    if(i < 0) i += sz;
+    if(i < 0 || i >= sz)
         naRuntimeError(ctx, "slice index %d out of bounds (size: %d)",
-                       i, naVec_size(v));
+                       i, sz);
     return i;
 }
 
diff --git a/simgear/nasal/codegen.c b/simgear/nasal/codegen.c
index 492b0f20..76050031 100644
--- a/simgear/nasal/codegen.c
+++ b/simgear/nasal/codegen.c
@@ -233,7 +233,7 @@ static void genHashElem(struct Parser* p, struct Token* t)
 {
     if(!t || t->type == TOK_EMPTY)
         return;
-    if(t->type != TOK_COLON)
+    if(t->type != TOK_COLON || !LEFT(t))
         naParseError(p, "bad hash/object initializer", t->line);
     if(LEFT(t)->type == TOK_SYMBOL) genScalarConstant(p, LEFT(t));
     else if(LEFT(t)->type == TOK_LITERAL) genExpr(p, LEFT(t));
@@ -560,9 +560,10 @@ static void genAssign(struct Parser* p, struct Token* t)
 
 static void genSlice(struct Parser* p, struct Token* t)
 {
+    if(!t) naParseError(p, "empty slice expression", -1);
     if(t->type == TOK_COLON) {
-        genExpr(p, LEFT(t));
-        genExpr(p, RIGHT(t));
+        if(LEFT(t))  genExpr(p, LEFT(t));  else emit(p, OP_PUSHNIL);
+        if(RIGHT(t)) genExpr(p, RIGHT(t)); else emit(p, OP_PUSHNIL);
         emit(p, OP_SLICE2);
     } else {
         genExpr(p, t);
-- 
2.39.5