prelude: Bug fix: specifying out of range index must panic

Fixes #732
gopherjs · hajimehoshi · Mar 15, 2018 · Mar 13, 2018 · Mar 14, 2018 · Mar 14, 2018
commit 77256a9d91efcbb5be06657cbbbde4e895ba02f0
diff --git a/compiler/prelude/prelude.go b/compiler/prelude/prelude.go
@@ -99,19 +99,19 @@ var $ifaceMethodExpr = function(name) {
 };

 var $subslice = function(slice, low, high, max) {
+  if (high === undefined) {
+    high = slice.$length;
+  }
+  if (max === undefined) {
+    max = slice.$capacity
+  }
  if (low < 0 || high < low || max < high || high > slice.$capacity || max > slice.$capacity) {
    $throwRuntimeError("slice bounds out of range");
  }
  var s = new slice.constructor(slice.$array);
  s.$offset = slice.$offset + low;
-  s.$length = slice.$length - low;
-  s.$capacity = slice.$capacity - low;
-  if (high !== undefined) {
-    s.$length = high - low;
-  }
-  if (max !== undefined) {
-    s.$capacity = max - low;
-  }
+  s.$length = high - low;
+  s.$capacity = max - low;
  return s;
 };


diff --git a/tests/misc_test.go b/tests/misc_test.go
@@ -623,3 +623,15 @@ func TestTypeConversion(t *testing.T) {
 		t.Fail()
 	}
 }
+
+func TestSliceOutOfRange(t *testing.T) {
+	defer func() {
+		if err := recover(); err == nil || !strings.Contains(err.(error).Error(), "slice bounds out of range") {
+			t.Fail()
+		}
+	}()
+
+	a := make([]byte, 4096)
+	b := a[8192:]
+	_ = b
+}
-Original file line number
+Diff line change
@@ -99,19 +99,19 @@ var $ifaceMethodExpr = function(name) {
     };
     var $subslice = function(slice, low, high, max) {
+      if (high === undefined) {
+        high = slice.$length;
+      }
+      if (max === undefined) {
+        max = slice.$capacity
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            dmitshur
  

      

      

      


        Mar 15, 2018


      
    

  


        
      
  
  
  
    

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        Mar 15, 2018


      
    

  


        
      
  
  
  
    

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+      }
       if (low < 0 || high < low || max < high || high > slice.$capacity || max > slice.$capacity) {
         $throwRuntimeError("slice bounds out of range");
       }
       var s = new slice.constructor(slice.$array);
       s.$offset = slice.$offset + low;
-      s.$length = slice.$length - low;
-      s.$capacity = slice.$capacity - low;
-      if (high !== undefined) {
-        s.$length = high - low;
-      }
-      if (max !== undefined) {
-        s.$capacity = max - low;
-      }
+      s.$length = high - low;
+      s.$capacity = max - low;
       return s;
     };
-          Expand Down