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Source file test/float_lit3.go

Documentation: test

  // errorcheck
  
  // Check flagging of invalid conversion of constant to float32/float64 near min/max boundaries.
  
  // Copyright 2014 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.
  
  package main
  
  // See float_lit2.go for motivation for these values.
  const (
  	two24   = 1.0 * (1 << 24)
  	two53   = 1.0 * (1 << 53)
  	two64   = 1.0 * (1 << 64)
  	two128  = two64 * two64
  	two256  = two128 * two128
  	two512  = two256 * two256
  	two768  = two512 * two256
  	two1024 = two512 * two512
  
  	ulp32 = two128 / two24
  	max32 = two128 - ulp32
  
  	ulp64 = two1024 / two53
  	max64 = two1024 - ulp64
  )
  
  var x = []interface{}{
  	float32(max32 + ulp32/2 - 1),             // ok
  	float32(max32 + ulp32/2 - two128/two256), // ok
  	float32(max32 + ulp32/2),                 // ERROR "constant 3\.40282e\+38 overflows float32"
  
  	float32(-max32 - ulp32/2 + 1),             // ok
  	float32(-max32 - ulp32/2 + two128/two256), // ok
  	float32(-max32 - ulp32/2),                 // ERROR "constant -3\.40282e\+38 overflows float32"
  
  	// If the compiler's internal floating point representation
  	// is shorter than 1024 bits, it cannot distinguish max64+ulp64/2-1 and max64+ulp64/2.
  	// gc uses fewer than 1024 bits, so allow it to print the overflow error for the -1 case.
  	float64(max64 + ulp64/2 - two1024/two256), // ok
  	float64(max64 + ulp64/2 - 1),              // GC_ERROR "constant 1\.79769e\+308 overflows float64"
  	float64(max64 + ulp64/2),                  // ERROR "constant 1\.79769e\+308 overflows float64"
  
  	float64(-max64 - ulp64/2 + two1024/two256), // ok
  	float64(-max64 - ulp64/2 + 1),              // GC_ERROR "constant -1\.79769e\+308 overflows float64"
  	float64(-max64 - ulp64/2),                  // ERROR "constant -1\.79769e\+308 overflows float64"
  }
  

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