You are right, I had forgot that GCC broke the libstdc++ ABI between 3.3 and 3.4 (not 3.x to 4.x though). That was 12 years ago, though, the ABI has been stable ever since [1].<p>I still would characterize it a fairly stable ABI, not something that &quot;can always break&quot;, especially compared with other vendors that break the library ABI every release.<p>[1] A new libstdc++ C++11 ABI was added in GCC 5.x but it is optional even in C++11 mode.