issue69110.go

     1  // run
     2  
     3  //go:build !goexperiment.swissmap
     4  
     5  // Copyright 2024 The Go Authors. All rights reserved.
     6  // Use of this source code is governed by a BSD-style
     7  // license that can be found in the LICENSE file.
     8  
     9  package main
    10  
    11  import (
    12  	"maps"
    13  	_ "unsafe"
    14  )
    15  
    16  func main() {
    17  	for i := 0; i < 100; i++ {
    18  		f()
    19  	}
    20  }
    21  
    22  const NB = 4
    23  
    24  func f() {
    25  	// Make a map with NB buckets, at max capacity.
    26  	// 6.5 entries/bucket.
    27  	ne := NB * 13 / 2
    28  	m := map[int]int{}
    29  	for i := 0; i < ne; i++ {
    30  		m[i] = i
    31  	}
    32  
    33  	// delete/insert a lot, to hopefully get lots of overflow buckets
    34  	// and trigger a same-size grow.
    35  	ssg := false
    36  	for i := ne; i < ne+1000; i++ {
    37  		delete(m, i-ne)
    38  		m[i] = i
    39  		if sameSizeGrow(m) {
    40  			ssg = true
    41  			break
    42  		}
    43  	}
    44  	if !ssg {
    45  		return
    46  	}
    47  
    48  	// Insert 1 more entry, which would ordinarily trigger a growth.
    49  	// We can't grow while growing, so we instead go over our
    50  	// target capacity.
    51  	m[-1] = -1
    52  
    53  	// Cloning in this state will make a map with a destination bucket
    54  	// array twice the size of the source.
    55  	_ = maps.Clone(m)
    56  }
    57  
    58  //go:linkname sameSizeGrow runtime.sameSizeGrowForIssue69110Test
    59  func sameSizeGrow(m map[int]int) bool
    60
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