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What is the LD_PRELOAD trick?


I came across a reference to it recently on proggit and (as of now) it is not explained.



I suspect this might be it, but I don't know for sure.


Source: Tips4allCCNA FINAL EXAM

Comments

  1. If you set LD_PRELOAD to the path of a shared object, that file will be loaded before any other library (including the C runtime, libc.so). So to run ls with a your special malloc() implementation, do this:

    $ LD_PRELOAD=/path/to/my/malloc.so /bin/ls

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  2. With LD_PRELOAD you can give libraries precedence.

    For example you can write a library which implement malloc and free. And by loading these with LD_PRELOAD your malloc and free will be executed rather than the standard ones.

    ReplyDelete
  3. You can override symbols in the stock libraries by creating a library with the same symbols and specifying the library in LD_PRELOAD.

    Some people use it to specify libraries in nonstandard locations, but LD_LIBRARY_PATH is better for that purpose.

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