linux清理函数问题

#include<stdio.h>
#include<unistd.h>
#include<pthread.h>

void CleanUp( void *arg )
{
    printf( "cleanup %s\n", (char *)arg );
}

void *Thr1( void *arg )
{
    pthread_cleanup_push( CleanUp, "thread 1 cleanup done\n" );
    printf( "thread 1 push done\n" );
    if( arg )
        pthread_exit( (void *)2 );
    else
        return ( (void *)1 );
    pthread_cleanup_pop( 0 );
}
void *Thr2( void *arg )
{
    pthread_cleanup_push( CleanUp, "thread 1 cleanup done\n" );
    printf( "thread 1 push done\n" );
    if( arg );
        pthread_cleanup_pop( 0 );
    else
        pthread_cleanup_pop( 1 );
    pthread_exit( (void *)2 );
}
int main( int argc, char **argv )
{
    pthread_t     tid1, tid2, tid3, tid4;
    void     *tret;

    pthread_create( &tid1, NULL, Thr1, (void *)0 );
    pthread_create( &tid2, NULL, Thr1, (void *)1 );
    pthread_create( &tid3, NULL, Thr2, (void *)0 );
    pthread_create( &tid4, NULL, Thr2, (void *)1 );
    pthread_join( tid1, &tret );
    pthread_join( tid2, &tret );
    pthread_join( tid3, &tret );
    pthread_join( tid4, &tret );

    exit( 0 );

}
程序编译不通过，出错原因是Thr2中if语句那一部分有问题，但是从push和pop要匹配使用的要求来看，Thr2的却只会执行pthread_cleanup_pop( 0 );或者pthread_cleanup_pop( 1 );那为什么会出错呢？求高人解答