Linux的环境变量LD_DEBUG调试so的加载

一个稍微有经验的Linux程序员都知道使用LD_LIBRARY_PATH 来临时设置加载器搜索动态链接库so的路径顺序。但另一个不为人知的环境变量是LD_DEBUG。这个变量可以提供非常详细的加载动态链接库的信息。

 

可以把LD_DEBUG设成以下值：

export LD_DEBUG=files     # 显示库的依赖性和加载的顺序

export LD_DEBUG=bindings  # 符号绑定

export LD_DEBUG=libs   # 显示加载器查找库时使用的路径的顺序

export LD_DEBUG=versions  # 版本依赖性

export LD_DEBUG=help  # LD_DEBUG的帮助信息

 

试一下把LD_DEBUG设成以上值之一，再随便运行一个程序试试。

一个试验：

root@vicarious:/home/kamus/projs/horoscope/bins# export LD_DEBUG=libs

root@vicarious:/home/kamus/projs/horoscope/bins# vim my.conf

     24360:   find library=libm.so.6 [0]; searching

     24360:   search cache=/etc/ld.so.cache

     24360:     trying file=/lib/x86_64-linux-gnu/libm.so.6

     24360:

     24360:   find library=libtinfo.so.5 [0]; searching

     24360:   search cache=/etc/ld.so.cache

     24360:     trying file=/lib/x86_64-linux-gnu/libtinfo.so.5

     24360:

     24360:   find library=libselinux.so.1 [0]; searching

     24360:   search cache=/etc/ld.so.cache

     24360:     trying file=/lib/x86_64-linux-gnu/libselinux.so.1

     24360:

     24360:   find library=libacl.so.1 [0]; searching

     24360:   search cache=/etc/ld.so.cache

     24360:     trying file=/lib/x86_64-linux-gnu/libacl.so.1

     24360:

     24360:   find library=libgpm.so.2 [0]; searching

     24360:   search cache=/etc/ld.so.cache

     24360:     trying file=/usr/lib/x86_64-linux-gnu/libgpm.so.2

     24360:

     24360:   find library=libc.so.6 [0]; searching

     24360:   search cache=/etc/ld.so.cache

     24360:     trying file=/lib/x86_64-linux-gnu/libc.so.6

     24360:

     24360:   find library=libdl.so.2 [0]; searching

     24360:   search cache=/etc/ld.so.cache

     24360:     trying file=/lib/x86_64-linux-gnu/libdl.so.2

     24360:

     24360:   find library=libattr.so.1 [0]; searching

     24360:   search cache=/etc/ld.so.cache

     24360:     trying file=/lib/x86_64-linux-gnu/libattr.so.1

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