On Thursday, 27 January 2022 at 16:46:59 UTC, Ali Çehreli wrote:
What I know is that weak symbols can be overridden by strong symbols during linking. Which means, if a function body is inlined which also has a weak symbol, some part of the program may be using the inlined definition and some other parts may be using the overridden definition. Thanks to separate compilation, they need not match hence the violation of the one-definition rule (ODR).
But the language requires ODR, so we can emit templates as weak_odr, telling the optimizer and linker that the symbols should be merged _and_ that ODR can be assumed to hold (i.e. inlining is OK). The onus of honouring ODR is on the user - not the compiler - because we allow the user to do separate compilation. Some more detailed explanation and example:
https://stackoverflow.com/questions/44335046/how-does-the-linker-handle-identical-template-instantiations-across-translation/44346057 -Johan
