On 2 Oct 2013 at 17:21, Emil Dotchevski wrote:
*ClassA.o* *0000000000059860 s __ZTIN5boost21errinfo_api_function_E* * * *ClassB.o* *0000000000059870 s __ZTIN5boost21errinfo_api_function_E *
Instantiating a template in two compilation units should not lead to link errors. That's why I can't understand why this happens.
Instantiating a template in two compilation units is no different to defining a non-static function twice. Unless its symbols are marked as composable (weak on ELF, selectany on PE) the linker will error. The only portable way of marking symbols as composable in C++ is the "inline" keyword which is auto-added by a C++ compiler for functions defined inline in a class definition. Given that most modern C++ compilers don't really take much hinting from inline anymore, inline now really equals "set this symbol to weak/selectany" i.e. don't link error if I instantiate this more than once. My point is that instantiating a template in multiple compilation units needs all of its member functions to be marked inline in order to prevent link error. Or, as the OP has found, one can hack around the problem by overriding symbol visibility and forcing multiple copies in each compilation unit. Niall -- Currently unemployed and looking for work. Work Portfolio: http://careers.stackoverflow.com/nialldouglas/