issue59411.go

     1  // run
     2  
     3  // Copyright 2023 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  package main
     8  
     9  import (
    10  	"math"
    11  	"reflect"
    12  )
    13  
    14  func main() {
    15  	for i := 0; i < 100; i++ {
    16  		f()
    17  		g()
    18  	}
    19  }
    20  
    21  func f() {
    22  	// Allocate map.
    23  	m := map[float64]int{}
    24  	// Fill to just before a growth trigger.
    25  	const N = 13 << 4 // 6.5 * 2 * 2^k
    26  	for i := 0; i < N; i++ {
    27  		m[math.NaN()] = i
    28  	}
    29  	// Trigger growth.
    30  	m[math.NaN()] = N
    31  
    32  	// Iterate through map.
    33  	i := 0
    34  	for range m {
    35  		if i == 6 {
    36  			// Partway through iteration, clear the map.
    37  			clear(m)
    38  		} else if i > 6 {
    39  			// If we advance to the next iteration, that's a bug.
    40  			panic("BAD")
    41  		}
    42  		i++
    43  	}
    44  	if len(m) != 0 {
    45  		panic("clear did not empty the map")
    46  	}
    47  }
    48  
    49  func g() {
    50  	// Allocate map.
    51  	m := map[float64]int{}
    52  	// Fill to just before a growth trigger.
    53  	const N = 13 << 4 // 6.5 * 2 * 2^k
    54  	for i := 0; i < N; i++ {
    55  		m[math.NaN()] = i
    56  	}
    57  	// Trigger growth.
    58  	m[math.NaN()] = N
    59  
    60  	// Iterate through map.
    61  	i := 0
    62  	v := reflect.ValueOf(m)
    63  	iter := v.MapRange()
    64  	for iter.Next() {
    65  		if i == 6 {
    66  			// Partway through iteration, clear the map.
    67  			v.Clear()
    68  		} else if i > 6 {
    69  			// If we advance to the next iteration, that's a bug.
    70  			panic("BAD")
    71  		}
    72  		i++
    73  	}
    74  	if v.Len() != 0 {
    75  		panic("clear did not empty the map")
    76  	}
    77  }
    78
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