Ian McCulloch <ianmcc@lorentz.leidenuniv.nl> writes:
Probably ;-) It's all there right under "One definition rule" in the standard.
3 Basic concepts 3.2 One definition rule
-5- There can be more than one definition of a class type (clause class), enumeration type (dcl.enum), inline function with external linkage (dcl.fct.spec), class template (clause temp), non-static function template (temp.fct), static data member of a class template (temp.static), member function [core 249: template of a class template ] (temp.mem.func), or template specialization for which some template parameters are not specified (temp.spec, temp.class.spec) in a program provided that each definition appears in a different translation unit, and provided the definitions satisfy the following requirements. Given such an entity named D defined in more than one translation unit, then
- each definition of D shall consist of the same sequence of tokens; and
- in each definition of D, corresponding names, looked up according to basic.lookup, shall refer to an entity defined within the definition of D, or shall refer to the same entity, after ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
To my reading of the standard, different typedef-names that are synonyms for the same type are the same entity with respect to the ODR, so I don't think any of this applies here.
If you limit the question to typedefs, you're right, but I'm not limiting the question to typedefs. The problem I'm discussing is this one: namespace { template <class T> typeof (T() + T()) add(T*, T*) { typeof(T() + T()) x; ... return x; } } If the declaration of x (or add, for that matter, I'm pretty sure) uses any names that refer to different entities in different TUs, it's an ODR violation. -- Dave Abrahams Boost Consulting http://www.boost-consulting.com