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Source file test/sliceopt.go

Documentation: test

  // errorcheck -0 -d=append,slice,ssa/prove/debug=1
  
  // Copyright 2015 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  // Check optimization results for append and slicing.
  
  package main
  
  func a1(x []int, y int) []int {
  	x = append(x, y) // ERROR "append: len-only update \(in local slice\)$"
  	return x
  }
  
  func a2(x []int, y int) []int {
  	return append(x, y)
  }
  
  func a3(x *[]int, y int) {
  	*x = append(*x, y) // ERROR "append: len-only update$"
  }
  
  // s1_if_false_then_anything
  func s1_if_false_then_anything(x **[]int, xs **string, i, j int) {
  	z := (**x)[0:i]
  	z = z[i : i+1]
  	println(z) // if we get here, then we have proven that i==i+1 (this cannot happen, but the program is still being analyzed...)
  
  	zs := (**xs)[0:i] // since i=i+1 is proven, i+1 is "in bounds", ha-ha
  	zs = zs[i : i+1]  // ERROR "Proved boolean IsSliceInBounds$"
  	println(zs)
  }
  
  func s1(x **[]int, xs **string, i, j int) {
  	var z []int
  	z = (**x)[2:]
  	z = (**x)[2:len(**x)] // ERROR "Proved boolean IsSliceInBounds$"
  	z = (**x)[2:cap(**x)] // ERROR "Proved IsSliceInBounds$"
  	z = (**x)[i:i]        // -ERROR "Proved IsSliceInBounds"
  	z = (**x)[1:i:i]      // ERROR "Proved boolean IsSliceInBounds$"
  	z = (**x)[i:j:0]
  	z = (**x)[i:0:j] // ERROR "Disproved IsSliceInBounds$"
  	z = (**x)[0:i:j] // ERROR "Proved boolean IsSliceInBounds$"
  	z = (**x)[0:]    // ERROR "slice: omit slice operation$"
  	z = (**x)[2:8]   // ERROR "Proved slicemask not needed$"
  	println(z)
  	z = (**x)[2:2]
  	z = (**x)[0:i]
  	z = (**x)[2:i:8] // ERROR "Disproved IsSliceInBounds$" "Proved IsSliceInBounds$"
  	z = (**x)[i:2:i] // ERROR "Proved IsSliceInBounds$" "Proved boolean IsSliceInBounds$"
  
  	z = z[0:i] // ERROR "Proved boolean IsSliceInBounds"
  	z = z[0:i : i+1]
  	z = z[i : i+1] // ERROR "Proved boolean IsSliceInBounds$"
  
  	println(z)
  
  	var zs string
  	zs = (**xs)[2:]
  	zs = (**xs)[2:len(**xs)] // ERROR "Proved IsSliceInBounds$" "Proved boolean IsSliceInBounds$"
  	zs = (**xs)[i:i]         // -ERROR "Proved boolean IsSliceInBounds"
  	zs = (**xs)[0:]          // ERROR "slice: omit slice operation$"
  	zs = (**xs)[2:8]
  	zs = (**xs)[2:2] // ERROR "Proved boolean IsSliceInBounds$"
  	zs = (**xs)[0:i] // ERROR "Proved boolean IsSliceInBounds$"
  
  	zs = zs[0:i]     // See s1_if_false_then_anything above to explain the counterfactual bounds check result below
  	zs = zs[i : i+1] // ERROR "Proved boolean IsSliceInBounds$"
  	println(zs)
  }
  

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