What C++ developers should know about globals (and the linker)
summary
Demonstrates a reproducible segfault when an executable links a static library and a shared library that both provide the same global, showing the constructor runs twice on the same address and the destructor runs twice, causing double free. Uses nm and objdump to inspect symbol tables and init sections, shows linker left-to-right resolution causing the mismatch, and presents fixes: inline variables in C++17, Meyers-style static locals, and a forced static reference trick, plus warnings about SIOF and performance and destructor-timing pitfalls.
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chapters (24)
- 0:00Introduction
- 4:58Library types
- 5:23Build setup
- 5:43Compilation commands
- 7:11The problem
- 8:16Debugging initialization
- 8:58Root cause analysis
- 9:55Linker mechanics
- 11:50Symbol tables
- 13:10Linker order
- 14:39Assembly investigation
- 15:37Double construction
- 18:09C++17 solution
- 18:36Pre-C++17 solutions
- 19:53Forced initialization
- 20:50Template tricks
- 22:28Static initialization order
- 23:31Singleton pitfalls
- 24:58Header definition strategy
- 25:52Destructor issues
- 26:13Dependency risks
- 26:59Robust headers
- 27:59Conclusion
- 28:45Q&A
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