Pardon the Interposition—Modifying and Improving Software Behavior with Interposers

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" summary

Interposers change program behavior at runtime using LD_PRELOAD and runtime symbol lookup like dlsym(RTLD_NEXT) to wrap C stubs for syscalls and libc functions. Example: a 300 line C interposer intercepts rename and stat to turn JIRA attachments into a two‑level store (local cache plus cloud PUT on successful rename, fetch-on-stat-miss) and runs in production for over three years. Another interposer (Maalox) records malloc/free traces and reveals a bucket sizing bug fixed by adding two bytes.

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" chapters (17)

1. 0:00Pardon the Interposition... Changing the behavior of software at runtime
2. 0:20My Background
3. 2:13Outline
4. 2:43Software often needs customization
5. 3:44Interposers (on UNIX)
6. 5:28atoi
7. 9:57Debugging malloc
8. 16:16JIRA attachments
9. 19:23Ideal JIRA attachment behavior
10. 20:34Options for Changing JIRA behavior
11. 23:17When you can't go high...then go low!
12. 24:00Uploading an attachment...
13. 26:11Changing rename() behavior...
14. 26:58Downloading an attachment...
15. 27:47Changing stat behavior...
16. 29:16Many many other uses
17. 33:08Summary

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