os: WriteFile failures with operation not permitted on iOS

[ericdream]

What version of Go are you using (go version)?

$ go version 1.16

Does this issue reproduce with the latest release?

I haven't used the latest release

What operating system and processor architecture are you using (go env)?

GO111MODULE="on"
GOARCH="arm64"
GOEXE=""
GOFLAGS="-mod=mod"
GOHOSTARCH="arm64"
GOHOSTOS="darwin"
GOINSECURE=""
GOOS="darwin"
GOPROXY="https://goproxy.cn,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_arm64"
GOVCS=""
GOVERSION="go1.16.15"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/9k/dt625z5x4sj2pcf0n5twxrc00000gn/T/go-build1768545817=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

I have a Go project that then compiles into an iOS library to use in an iOS project.

Code snippets
ioutil.WriteFile(path, data, os.ModePerm)

Write some data to a file using ioutil.WriteFile

What did you expect to see?

return error is nil

What did you see instead?

The error of operation not permitted occasionally appears on some iphone phones
:open /xxx/xxx.json: operation not permitted

[bcmills]

That seems likely to be either an application error or a bug in the iOS filesystem or kernel. I suggest that you check for race conditions in the application (is something perhaps changing the permissions of the parent directory?), and consider escalating the bug to Apple.

If you can reproduce the failure mode in a simple, standalone test, it may be possible to reproduce it on the Go project's ios builders, in which case it might be possible to develop a workaround, but without a reproducer I don't think there's anything we can feasibly do to address this.

(CC @golang/ios)

[bcmills]

$ go version 1.16

Per the Go release policy, only the two most recent major releases of Go are supported — currently Go 1.18 and 1.19, and soon Go 1.19 and 1.20. If you can reproduce this problem on a supported version, please post the reproducer and reopen this issue.