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2de449e7a0
Add larger comment explaining testing methodology, and derive tests arithmetically. (These tests are checking rounding again; the derived tests they replace were checking exact values.) LGTM=r, gri R=gri, r CC=golang-codereviews https://golang.org/cl/100660044
49 lines
1.8 KiB
Go
49 lines
1.8 KiB
Go
// errorcheck
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// Check flagging of invalid conversion of constant to float32/float64 near min/max boundaries.
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// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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// See float_lit2.go for motivation for these values.
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const (
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two24 = 1.0 * (1 << 24)
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two53 = 1.0 * (1 << 53)
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two64 = 1.0 * (1 << 64)
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two128 = two64 * two64
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two256 = two128 * two128
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two512 = two256 * two256
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two768 = two512 * two256
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two1024 = two512 * two512
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ulp32 = two128 / two24
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max32 = two128 - ulp32
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ulp64 = two1024 / two53
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max64 = two1024 - ulp64
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)
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var x = []interface{}{
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float32(max32 + ulp32/2 - 1), // ok
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float32(max32 + ulp32/2 - two128/two256), // ok
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float32(max32 + ulp32/2), // ERROR "constant 3\.40282e\+38 overflows float32"
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float32(-max32 - ulp32/2 + 1), // ok
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float32(-max32 - ulp32/2 + two128/two256), // ok
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float32(-max32 - ulp32/2), // ERROR "constant -3\.40282e\+38 overflows float32"
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// If the compiler's internal floating point representation
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// is shorter than 1024 bits, it cannot distinguish max64+ulp64/2-1 and max64+ulp64/2.
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// gc uses fewer than 1024 bits, so allow it to print the overflow error for the -1 case.
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float64(max64 + ulp64/2 - two1024/two256), // ok
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float64(max64 + ulp64/2 - 1), // GC_ERROR "constant 1\.79769e\+308 overflows float64"
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float64(max64 + ulp64/2), // ERROR "constant 1\.79769e\+308 overflows float64"
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float64(-max64 - ulp64/2 + two1024/two256), // ok
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float64(-max64 - ulp64/2 + 1), // GC_ERROR "constant -1\.79769e\+308 overflows float64"
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float64(-max64 - ulp64/2), // ERROR "constant -1\.79769e\+308 overflows float64"
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}
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