Add warning for array index out of range

Author: totalspectrum

Changelog.txt

@@ -1,3 +1,6 @@
+Version 6.6.2
+- Added warnings for constant array indices out of bounds
+
 Version 6.6.1
 - Changed type of `dat` array in C++ output to `unsigned char`
 - Fixed function type usage in -2nu for some Spin method pointers

expr.c

@@ -2254,6 +2254,20 @@ GetArrayBase(AST *arraytype)
     return NULL;
 }
 
+AST *
+GetArraySize(AST *arraytype)
+{
+    AST *lim;
+    arraytype = RemoveTypeModifiers(arraytype);
+    if (arraytype->kind == AST_ARRAYTYPE) {
+        lim = arraytype->right;
+        if (lim) {
+            return lim;
+        }
+    }
+    return NULL;
+}
+
 /* find minimum alignment for a type */
 int TypeAlign(AST *typ)
 {

expr.h

@@ -81,6 +81,10 @@ int IsArrayOrPointerSymbol(Symbol *);
 int PointerTypeIncrement(AST *typ);
 // get base of an array type
 AST *GetArrayBase(AST *type);
+
+// get size of array type
+AST *GetArraySize(AST *type);
+
 // create an array based on a type and expression or expression list
 // the elements of the list can either be simple expressions (giving the array size)
 // or AST_RANGE (giving the start and end indices)

frontends/types.c

@@ -1968,6 +1968,23 @@ static AST *doCheckTypes(AST *ast)
         } else if (IsArrayType(lefttype)) {
             // convert the array index to subtract base
             AST *base = GetArrayBase(lefttype);
+            if (IsConstExpr(ast->right)) {
+                int idx = EvalConstExpr(ast->right);
+                int low = 0;
+                if (!base || IsConstExpr(base)) {
+                    low = base ? EvalConstExpr(base) : 0;
+                    if (idx < low) {
+                        WARNING(ast, "Array index %d is less than array start (%d)", idx, low);
+                    }
+                }
+                AST *aSize = GetArraySize(lefttype);
+                if (IsConstExpr(aSize)) {
+                    int high = EvalConstExpr(aSize) + low - 1;
+                    if (idx > high) {
+                        WARNING(ast, "Array index %d is above end of array (%d)", idx, high);
+                    }
+                }
+            }
             if (base) {
                 ast->right = AstOperator('-', ast->right, base);
             }

version.h

@@ -6,8 +6,8 @@
 
 #define VERSION_MAJOR 6
 #define VERSION_MINOR 6
-#define VERSION_REV   1
-//#define BETA "-beta"
+#define VERSION_REV   2
+#define BETA "-beta"
 
 #define VERSIONSTR version_string