C++ Thread-Local Storage Performance Pitfalls: 0 + 0 > 0?

This article delves into the performance implications of using thread_local variables in C++. By analyzing assembly code, the author reveals significant performance discrepancies in different scenarios, particularly with thread_local variables having constructors and those used in shared libraries. Even simple accesses can suffer dramatic slowdowns due to constructor calls, dynamic loading of shared libraries, and other factors. The article concludes with performance optimization guidelines and discusses future improvements, aiming to help developers avoid thread_local performance traps.
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