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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:23:18 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:23:18 +0000 |
commit | 43a123c1ae6613b3efeed291fa552ecd909d3acf (patch) | |
tree | fd92518b7024bc74031f78a1cf9e454b65e73665 /test/nil.go | |
parent | Initial commit. (diff) | |
download | golang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.tar.xz golang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.zip |
Adding upstream version 1.20.14.upstream/1.20.14upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'test/nil.go')
-rw-r--r-- | test/nil.go | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/test/nil.go b/test/nil.go new file mode 100644 index 0000000..f8300bf --- /dev/null +++ b/test/nil.go @@ -0,0 +1,180 @@ +// run + +// Copyright 2009 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. + +// Test nil. + +package main + +import ( + "fmt" + "time" +) + +type T struct { + i int +} + +type IN interface{} + +func main() { + var i *int + var f *float32 + var s *string + var m map[float32]*int + var c chan int + var t *T + var in IN + var ta []IN + + i = nil + f = nil + s = nil + m = nil + c = nil + t = nil + i = nil + ta = make([]IN, 1) + ta[0] = nil + + _, _, _, _, _, _, _, _ = i, f, s, m, c, t, in, ta + + arraytest() + chantest() + maptest() + slicetest() +} + +func shouldPanic(f func()) { + defer func() { + if recover() == nil { + panic("not panicking") + } + }() + f() +} + +func shouldBlock(f func()) { + go func() { + f() + panic("did not block") + }() + time.Sleep(1e7) +} + +// nil array pointer + +func arraytest() { + var p *[10]int + + // Looping over indices is fine. + s := 0 + for i := range p { + s += i + } + if s != 45 { + panic(s) + } + + s = 0 + for i := 0; i < len(p); i++ { + s += i + } + if s != 45 { + panic(s) + } + + // Looping over values is not. + shouldPanic(func() { + for i, v := range p { + s += i + v + } + }) + + shouldPanic(func() { + for i := 0; i < len(p); i++ { + s += p[i] + } + }) +} + +// nil channel +// select tests already handle select on nil channel + +func chantest() { + var ch chan int + + // nil channel is never ready + shouldBlock(func() { + ch <- 1 + }) + shouldBlock(func() { + <-ch + }) + shouldBlock(func() { + x, ok := <-ch + println(x, ok) // unreachable + }) + + if len(ch) != 0 { + panic(len(ch)) + } + if cap(ch) != 0 { + panic(cap(ch)) + } +} + +// nil map + +func maptest() { + var m map[int]int + + // nil map appears empty + if len(m) != 0 { + panic(len(m)) + } + if m[1] != 0 { + panic(m[1]) + } + if x, ok := m[1]; x != 0 || ok { + panic(fmt.Sprint(x, ok)) + } + + for k, v := range m { + panic(k) + panic(v) + } + + // can delete (non-existent) entries + delete(m, 2) + + // but cannot be written to + shouldPanic(func() { + m[2] = 3 + }) +} + +// nil slice + +func slicetest() { + var x []int + + // nil slice is just a 0-element slice. + if len(x) != 0 { + panic(len(x)) + } + if cap(x) != 0 { + panic(cap(x)) + } + + // no 0-element slices can be read from or written to + var s int + shouldPanic(func() { + s += x[1] + }) + shouldPanic(func() { + x[2] = s + }) +} |