https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46283
--- Comment #3 from Tor Myklebust <tmyklebu at gmail dot com> --- On Sat, Jul 24, 2021 at 6:45 AM pinskia at gcc dot gnu.org <gcc-bugzi...@gcc.gnu.org> wrote: > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46283 > > --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- > ((a *)0)->foo::x() > > ((T *)0)->foo::x() > > Both are those are undefined because you are calling a method of a NULL > pointer. That's true. In both cases, one can modify this code, for instance by writing (new a)->foo::x() or (new T)->foo::x(), or by statically instantiating an object of the appropriate type, without changing the relevant name lookup behaviour. > (In reply to Andrew Pinski from comment #1) > > I think the code should be rejected. Here is what Comeau online says: > > "ComeauTest.c", line 14: error: ambiguous class member reference -- type > > "b::foo" > > (declared at line 4) used in preference to type "a::foo" (declared > > at line 10) > > And clang rejects this: > <source>:14:41: error: lookup of 'foo' in member access expression is > ambiguous > void b::go() { printf("%i\n", ((a *)0)->foo::x()); } > ^ > <source>:10:13: note: lookup in the object type 'a' refers here > typedef b foo; > ^ > <source>:4:20: note: lookup from the current scope refers here > typedef struct a foo; > ^ It appears (through playing with Matt Godbolt's Compiler Explorer) that a change was made between clang 5.0.1 and clang 6.0.0 that made clang match gcc's behaviour. 5.0.1 gives the errors above, while 6.0.0 compiles the code without warnings or errors.
