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syscall: syscall.FD_CLOEXEC is not equal with syscall.O_CLOEXEC #25515

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hustcat opened this issue May 23, 2018 · 2 comments
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syscall: syscall.FD_CLOEXEC is not equal with syscall.O_CLOEXEC #25515

hustcat opened this issue May 23, 2018 · 2 comments

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@hustcat
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@hustcat hustcat commented May 23, 2018

Why syscall.FD_CLOEXEC is not equal with syscall.O_CLOEXEC?However, FD_CLOEXEC is equal with O_CLOEXEC in glibc.

In go:

    fmt.Printf("FD_CLOEXEC=%x\n", syscall.FD_CLOEXEC)
    fmt.Printf("O_CLOEXEC=%x\n", syscall.O_CLOEXEC)
    fmt.Printf("O_NONBLOCK=%x\n", syscall.O_NONBLOCK)

FD_CLOEXEC=1
O_CLOEXEC=80000
O_NONBLOCK=800

In glibc:

#include <sys/eventfd.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>

int main(int argc, char *argv[]){
    printf("EFD_NONBLOCK=%x\n", EFD_NONBLOCK);
    printf("O_NONBLOCK=%x\n", O_NONBLOCK);
    printf("EFD_CLOEXEC=%x\n", EFD_CLOEXEC);
    printf("O_CLOEXEC=%x\n", O_CLOEXEC);
}

EFD_NONBLOCK=800
O_NONBLOCK=800
EFD_CLOEXEC=80000
O_CLOEXEC=80000

And more, why EFD_NONBLOCK is not exist in go?

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

# go version     
go version go1.7.1 linux/amd64

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

# go env
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/data/go"
GORACE=""
GOROOT="/usr/local/go_1.7.1"
GOTOOLDIR="/usr/local/go_1.7.1/pkg/tool/linux_amd64"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build674153237=/tmp/go-build"
CXX="g++"
CGO_ENABLED="1"
@hustcat hustcat changed the title syscall.FD_CLOEXEC is not equal with syscall.O_CLOEXEC syscall: syscall.FD_CLOEXEC is not equal with syscall.O_CLOEXEC May 23, 2018
@tklauser
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@tklauser tklauser commented May 23, 2018

And more, EFD_NONBLOCK is not exist in go.

EFD_NONBLOCK is part of golang.org/x/sys/unix which should be used instead of package syscall.

@tklauser
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@tklauser tklauser commented May 23, 2018

Also, the given C program is checking the EFD_* constants while the Go program tests the FD_* constants. These are different things. As I see it, the current values of FD_CLOEXEC and FD_NONBLOCK match the respective values in glibc. FD_CLOEXEC is not the same value as O_CLOEXEC in glibc either, i.e. it matches the values in package syscall:

cat foo.c && gcc foo.c && ./a.out
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>

int main(int argc, char *argv[]){
	printf("FD_CLOEXEC=%x\n", FD_CLOEXEC);
	printf("O_CLOEXEC=%x\n", O_CLOEXEC);
}

FD_CLOEXEC=1
O_CLOEXEC=80000
@tklauser tklauser closed this May 23, 2018
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