CHECK_CXX_SOURCE_COMPILES("
    #include<fcntl.h>
    #include<unistd.h>
    int main(int,char*[]){
      int f = open(\"/x/y\", O_RDONLY);
      char buf[100];
      return pread(f, buf, 100, 1000) == 0;
    }"
  HAS_PREAD
)