树莓派编译程序时报错：virtual memory exhausted: Cannot allocate memory

一、原因分析： 

　　树莓派内存太小，编译程序会出现virtual memory exhausted: Cannot allocate memory的问题，可以用swap扩展内存的方法。

二、解决方法：

　　安装dphys-swapfile软件包，安装后默认设置的swap大小为物理内存的两倍，最大为2G。   

　　Autogenerate and use a swap file

　　This init.d script exists so one does not need to have a fixed size swap partition. Instead install without swap partition and then run this, with file size (re-)computed automatically to fit the current RAM size.

　　By default (and hence on installation) it creates swapfile twice as big as the present RAM amount with an upper limit of 2 GB.

 参考：https://packages.debian.org/jessie/admin/dphys-swapfile