A Shared Library and Dynamic Linking Monitor
MONDO: A Shared Library and Dynamic Linking Monitor C. Donour Sizemore, Jacob R. Lilly, and David M. Beazley Department of Computer Science University of Chicago Chicago, Illinois 60637 {donour,jrlilly,beazley}@cs.uchicago.edu March 15, 2003 Abstract ically loadable extension modules. Similarly, dy- namic modules are commonly used to extend web Dynamic modules are one of the most attractive servers, browsers, and other large programming en- features of modern scripting languages. Dynamic vironments. modules motivate programmers to build their ap- Although dynamic linking offers many benefits plications as small components, then glue them to- such as increased modularity, simplified mainte- gether. They rely on the runtime linker to assemble nance, and extensibility, it has also produced a con- components and shared libraries as the application siderable amount of programmer confusion. Few runs. MONDO, a new debugging tool, provides pro- programmers would claim to really understand how grammers with the ability to monitor in real-time dynamic linking actually works. Moreover, the run- the dynamic linking of a program. MONDO sup- time linking process depends heavily on the system plies programmers with a graphical interface show- configuration, environment variables, subtle com- ing library dependencies, listing symbol bindings, piler and linker options, and the flags passed to low- and providing linking information used to uncover level dynamic loader. The interaction of these pieces subtle programming errors related to the use of tends to produce a very obscured picture of what shared libraries. The use of MONDO requires no is actually going on inside an application that uses modification to existing code or any changes to the shared libraries.
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