The truth is in the standard (3.2 One definition rule) : No translation unit shall contain more than one definition of any variable, function, class type, enumeration type or template. […] Every program shall contain exactly one definition of every non-inline function or object that is used in that program; no diagnostic required. The definition … Read more
Lambda’s scope can implicitly capture variables within its reaching scope. Your variables are in the reaching scope, since they are local to the (main) function that defines the lambda. However, there are certain criteria in which variables can be captured via this mechanism, as mentioned in [expr.prim.lambda]/12: A lambda-expression with an associated capture-default that does … Read more
It looks like defect report 1400: Function pointer equality deals with this issue and seems to me to say that it is okay to do this optimization but as comments indicate, there is disagreement. It says (emphasis mine): According to 5.10 [expr.eq] paragraph 2, two function pointers only compare equal if they point to the … Read more
This boils down to whether or not a lambda’s type differs across translation units. If it does, it may affect template argument deduction and potentially cause different functions to be called – in what are meant to be consistent definitions. That would violate the ODR (see below). However, that isn’t intended. In fact, this problem … Read more
It’s just an arbitrary definition, used by the standard to specify when you must provide a definition for an entity (as opposed to just a declaration). The standard doesn’t say just “used”, because this can be interpreted diversely depending on context. And some ODR-use doesn’t really correspond to what one would normally associate with “use”; … Read more
Oh man, one of my pet peeves. inline is more like static or extern than a directive telling the compiler to inline your functions. extern, static, inline are linkage directives, used almost exclusively by the linker, not the compiler. It is said that inline hints to the compiler that you think the function should be … Read more