如何定义自己的线程函数与第三方系统兼容

在多线程的环境中，我们需要有线程创建函数来创建需要的线程，一般的系统都是有自己的线程创建函数的，但是有的系统没有，或者说两个系统不兼容，那么我们就需要有自己的线程创建函数来兼容第三方，一般在模拟线程创建的时候都是用进程来实现的，下面就是一个例子：

static intpthread_create(sp_pthread_t *thread, const void *attr,    void *(*thread_start)(void *), void *arg){pid_t pid;struct pam_ctxt *ctx = arg;sshpam_thread_status = -1;switch ((pid = fork())) {case -1:error("fork(): %s", strerror(errno));return (-1);case 0:close(ctx->pam_psock);ctx->pam_psock = -1;thread_start(arg);_exit(1);default:*thread = pid;close(ctx->pam_csock);ctx->pam_csock = -1;sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler);return (0);}}

typedef pthread_t sp_pthread_t;#elsetypedef pid_t sp_pthread_t;#endifstruct pam_ctxt {sp_pthread_t pam_thread;int pam_psock;int pam_csock;int pam_done;};static void sshpam_free_ctx(void *);static struct pam_ctxt *cleanup_ctxt;#ifndef UNSUPPORTED_POSIX_THREADS_HACK/* * Simulate threads with processes. */static int sshpam_thread_status = -1;static mysig_t sshpam_oldsig;static voidsshpam_sigchld_handler(int sig){signal(SIGCHLD, SIG_DFL);if (cleanup_ctxt == NULL)return;/* handler called after PAM cleanup, shouldn't happen */if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG)    <= 0) {/* PAM thread has not exitted, privsep slave must have */kill(cleanup_ctxt->pam_thread, SIGTERM);if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, 0)    <= 0)return; /* could not wait */}if (WIFSIGNALED(sshpam_thread_status) &&    WTERMSIG(sshpam_thread_status) == SIGTERM)return;/* terminated by pthread_cancel */if (!WIFEXITED(sshpam_thread_status))sigdie("PAM: authentication thread exited unexpectedly");if (WEXITSTATUS(sshpam_thread_status) != 0)sigdie("PAM: authentication thread exited uncleanly");}/* ARGSUSED */static voidpthread_exit(void *value){_exit(0);}