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

$ go version
go version go1.12.4 linux/amd64

Does this issue reproduce with the latest release?

yes

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

$ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/data/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build504982591=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I am developing a static library with GO for use in C/C++
Here is an example:

shell>cat demo.c 

/**
 *  
 *  bulid：gcc -g ./demo.c -I./ -L./ -lcdemo -lpthread -o demo
 * 
 */
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include "libcdemo.h"

GoString toGoString(const char *str)
{
    int len = strlen(str);
    GoString gostr = {str, len};
    return gostr;
}
int init_daemon(void) 
{ 
        int pid; 
        int i; 

        signal(SIGTTOU,SIG_IGN);
        signal(SIGTTIN,SIG_IGN);
        signal(SIGTSTP,SIG_IGN);
        signal(SIGHUP,SIG_IGN);

        pid = fork();
        if(pid > 0) {
                exit(0); //exit parent
        }
        else if(pid < 0) { 
                return -1;
        }

        setsid();

        pid=fork();
        if( pid > 0) {
                exit(0);
        }
        else if( pid< 0) {
                return -1;
        }
 
        for(i=0;i< NOFILE;close(i++));
 
        chdir("/data/demo/");

        umask(0);

        signal(SIGCHLD,SIG_IGN); 

        return 0;
}
int main()
{
    printf("demo start... \r\n");

    //TODO todo something
    // ...
    //sleep(3);
    //call daemon
    init_daemon();
    sleep(3);
    //-----------------------call go function--------------------
    openlog("testlogs", LOG_CONS | LOG_PID, 0);  
    syslog(LOG_USER | LOG_INFO ,"This is a syslog test message generated by program \n");  
    //TODO todo something
    //Bar();
    syslog(LOG_USER | LOG_INFO ,"bar2:%s \n",Bar2());
    syslog(LOG_USER | LOG_INFO ,"bar2:%s \n","Hello C");

    // ...
    sleep(3);
    closelog();  
    return 0;
}

The go code:

shell>cat cdemo.go 

package main

import "C"
import (
        "fmt"
)

func main() {
        fmt.Println(Bar2())
        return
}

//export Bar2
func Bar2() *C.char {
        return C.CString("Hello World From Go!")
}

Compile the static library and use it

shell>go build -x -v -gcflags "-N -l" -buildmode=c-archive -o libcdemo.a .
shell>ls
cdemo.go  libcdemo.a  libcdemo.h
shell>mv libcdemo* cdemo_test
shell>cd cdemo_test
shell>ls
demo.c  libcdemo.a  libcdemo.h
shell>gcc -g ./demo.c -I./ -L./ -lcdemo -lpthread -o demo
shell>ls
demo  demo.c  libcdemo.a  libcdemo.h
shell>./demo
demo start...
shell>pstack 16968
#0  0x0000003dfe80b68c in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1  0x0000000000401583 in _cgo_wait_runtime_init_done ()
#2  0x000000000040149c in Bar2 ()
#3  0x00000000004013d4 in main ()

What did you expect to see?

Hello World From Go!

What did you see instead?

The cgo blocked!

What do I need to do?