c - 为什么在不同进程中多次创建共享库中的静态变量？

Question

我的代码是共享库，它应该只有一个库实例吗？

我有一个静态变量，每次调用函数时都会更改它。而且它似乎一直在恢复到默认值。

我做错了什么？

我用它编译的

gcc -fPIC -Wall -shared -lpam -o pam_hook.so pam_hook.c

代码:

static int is_reqest_sent=0;

int PAM_LOG_args( char * function, int argc, const char ** argv,int flags,pam_handle_t *pamh)
{
    int ret = 0,i=0;
    char  **pam_envlist, **pam_env;



    FILE * fp = fopen ("/var/log/pam_flow.log","a");
    fprintf(fp,"function :  %s flags %d  \n",function,flags);
    fprintf (fp, "my  PID: %d  parent PID %d is_reqest_sent : %d\n",
            getpid(),getppid(),is_reqest_sent);
    /* export PAM environment */
    if (pamh!=NULL)
    {
        if ((pam_envlist = pam_getenvlist(pamh)) != NULL) 
        for (pam_env = pam_envlist; *pam_env != NULL; ++pam_env) {
            fprintf(fp,"%s\n",*pam_env);
            free(*pam_env);
        }

    }
    for(i=0;i<=argc-1;i++)      
        fprintf(fp,"%s\n",argv[i]);

    fclose(fp);


  return ret;
}
int isRequestSent(void)
{

    if(is_reqest_sent==0)
    {
        is_reqest_sent=1;
        return 0;
    }
    else
    {
        is_reqest_sent=0;
        return 1;
    }
}

PAM_EXTERN int pam_sm_authenticate(pam_handle_t *pamh, int flags, int argc, const char **argv) {
    const char * password=NULL;
    struct passwd *pwd;
    const char *user;
    int pam_err=0;

    PAM_LOG_args( "pam_sm_authenticate", argc, argv,flags,pamh);
    printTime();
        /* identify user */
    pam_err = pam_get_user(pamh, &user, NULL);
    if (pam_err != PAM_SUCCESS)
    {
            return (pam_err);
    }

    if ((pwd = getpwnam(user)) == NULL)
    {
            return (PAM_USER_UNKNOWN);
    }
    /*note : if user is not deefined pawsword return will be "^H$^M^?INCORRECT^@" */
    pam_err  = pam_get_authtok(pamh, PAM_AUTHTOK, &password , NULL);
    if (pam_err!=PAM_SUCCESS)
    {
            return (PAM_AUTH_ERR);
    }


    if(isRequestSent()==0)
    {
        debugPrint("isRequestSent return 0");   
    } 
        return (PAM_SUCCESS);
}
PAM_EXTERN int pam_sm_open_session(pam_handle_t *pamh, int flags, int argc, const char **argv) {
    PAM_LOG_args( "pam_sm_open_session ", argc, argv,flags,pamh);
    debugPrint("pam_sm_open_session ","",0,pamh);
    printTime();
    printLogoutLoging(pamh,1);
    return PAM_SUCCESS;
}

并打印出我必须打印 is_reqest_sent 的值和进程 pid:

函数:pam_sm_authenticate 标志 1

my  PID: 9521  parent PID 9514 is_reqest_sent : 0

函数:pam_sm_open_session 标志 0

my  PID: 9521  parent PID 9514 is_reqest_sent : 1

函数:pam_sm_authenticate 标志 1

my  PID: 9528  parent PID 9514 is_reqest_sent : 0

Answer 1

全局变量不是共享的，因为每个进程都在使用其自己的 地址空间。代码是共享的，内存不是。

要在进程之间共享内存，请使用 "Shared Memory" (aka SHM) .