On Mon, 2017-09-04 at 10:33 +0100, Jonathan Wakely wrote: > On 3 September 2017 at 11:43, Andrew Makhorin wrote: > > Why x used to initialize y identifies not the same object as x used in > > printf though x is the same identifier within the same block scope? > > Because that's how scope and visibility works in the C programming > language. A name is only in scope after it has been declared. Get a > good book on C programming. > Thank you for your reply. I think the ISO C Standard is a good book. The subsection 6.2.1 "Scopes of identifiers" says: Different entities designated by the same identifier either have different scopes, or are in different name spaces. [...] Two identifiers have the same scope if and only if their scopes terminate at the same point. In my example program x used in printf has block scope which overlaps the file scope where other x is declared. Thus, the behavior of my example program is undefined, because x is used to initialize y before it is assigned an initial value (this is similar to the case when a goto jumps into a block bypassing possible initialization of variables declared within that block).
