On 09/24/13 10:46, Laine Stump wrote:
On 09/23/2013 08:03 PM, Laszlo Ersek wrote:
... and adapt functions that would cast away the new const qualifier.
Given
typedef virSocketAddr *virSocketAddrPtr;
Compare the parse trees of the following two declarations:
(a) const virSocketAddrPtr addr; (b) const virSocketAddr *addr;
Umm.. Eric? A little help? :-)
The grammar rules that I used for the AST derivation can be looked up eg. in the final C11 draft, http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf Section 6.7 "Declarations". But, the short version is really just that type qualifiers (like const & volatile) don't enter the typedef name; they qualify the variable being declared. const virSocketAddrPtr addr; virSocketAddrPtr const addr; these are equivalent, they mean the same thing, a constant pointer to a variable object. Expanding the typedef, that's written as virSocketAddr *const addr; (It is closer in appearance to the second form above.) If you want to qualify the target of the pointer, you must say one of the following: (i) const virSocketAddr *addr; (ii) virSocketAddr const *addr; (iii) typedef const virSocketAddr *constVirSocketAddrPtr; constVirSocketAddrPtr addr; (iv) typedef virSocketAddr const *constVirSocketAddrPtr; constVirSocketAddrPtr addr; In general I disapprove of typedefs: they seem to be friendly by saving you the repeated typing of "struct" and "*". Until they trick you :) Laszlo