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Source file test/sliceopt.go

Documentation: test

     1  // errorcheck -0 -d=append,slice,ssa/prove/debug=1
     2  
     3  // Copyright 2015 The Go Authors. All rights reserved.
     4  // Use of this source code is governed by a BSD-style
     5  // license that can be found in the LICENSE file.
     6  
     7  // Check optimization results for append and slicing.
     8  
     9  package main
    10  
    11  func a1(x []int, y int) []int {
    12  	x = append(x, y) // ERROR "append: len-only update \(in local slice\)$"
    13  	return x
    14  }
    15  
    16  func a2(x []int, y int) []int {
    17  	return append(x, y)
    18  }
    19  
    20  func a3(x *[]int, y int) {
    21  	*x = append(*x, y) // ERROR "append: len-only update$"
    22  }
    23  
    24  // s1_if_false_then_anything
    25  func s1_if_false_then_anything(x **[]int, xs **string, i, j int) {
    26  	z := (**x)[0:i]
    27  	z = z[i : i+1]
    28  	println(z) // if we get here, then we have proven that i==i+1 (this cannot happen, but the program is still being analyzed...)
    29  
    30  	zs := (**xs)[0:i] // since i=i+1 is proven, i+1 is "in bounds", ha-ha
    31  	zs = zs[i : i+1]  // ERROR "Proved boolean IsSliceInBounds$"
    32  	println(zs)
    33  }
    34  
    35  func s1(x **[]int, xs **string, i, j int) {
    36  	var z []int
    37  	z = (**x)[2:]
    38  	z = (**x)[2:len(**x)] // ERROR "Proved boolean IsSliceInBounds$"
    39  	z = (**x)[2:cap(**x)] // ERROR "Proved IsSliceInBounds$"
    40  	z = (**x)[i:i]        // -ERROR "Proved IsSliceInBounds"
    41  	z = (**x)[1:i:i]      // ERROR "Proved boolean IsSliceInBounds$"
    42  	z = (**x)[i:j:0]
    43  	z = (**x)[i:0:j] // ERROR "Disproved IsSliceInBounds$"
    44  	z = (**x)[0:i:j] // ERROR "Proved boolean IsSliceInBounds$"
    45  	z = (**x)[0:]    // ERROR "slice: omit slice operation$"
    46  	z = (**x)[2:8]   // ERROR "Proved slicemask not needed$"
    47  	println(z)
    48  	z = (**x)[2:2]
    49  	z = (**x)[0:i]
    50  	z = (**x)[2:i:8] // ERROR "Disproved IsSliceInBounds$" "Proved IsSliceInBounds$"
    51  	z = (**x)[i:2:i] // ERROR "Proved IsSliceInBounds$" "Proved boolean IsSliceInBounds$"
    52  
    53  	z = z[0:i] // ERROR "Proved boolean IsSliceInBounds"
    54  	z = z[0:i : i+1]
    55  	z = z[i : i+1] // ERROR "Proved boolean IsSliceInBounds$"
    56  
    57  	println(z)
    58  
    59  	var zs string
    60  	zs = (**xs)[2:]
    61  	zs = (**xs)[2:len(**xs)] // ERROR "Proved IsSliceInBounds$" "Proved boolean IsSliceInBounds$"
    62  	zs = (**xs)[i:i]         // -ERROR "Proved boolean IsSliceInBounds"
    63  	zs = (**xs)[0:]          // ERROR "slice: omit slice operation$"
    64  	zs = (**xs)[2:8]
    65  	zs = (**xs)[2:2] // ERROR "Proved boolean IsSliceInBounds$"
    66  	zs = (**xs)[0:i] // ERROR "Proved boolean IsSliceInBounds$"
    67  
    68  	zs = zs[0:i]     // See s1_if_false_then_anything above to explain the counterfactual bounds check result below
    69  	zs = zs[i : i+1] // ERROR "Proved boolean IsSliceInBounds$"
    70  	println(zs)
    71  }
    72  

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