On 20 May 2011, at 20:30, Joe Buck wrote: > On Fri, May 20, 2011 at 09:32:16AM -0700, Jason Merrill wrote: >> G++ has had a long-standing bug with unqualified name resolution in >> templates: if we didn't find any declaration when looking up a name in >> the template definition, we would do an additional unqualified lookup at >> the point of instantiation. This led to incorrectly finding >> namespace-scope functions declared later (29131) and member functions of >> dependent bases (24163). This patch fixes that bug. > > I get the impression that most competing C++ compilers (other than the > old HP compiler) were (or are) very loose about that rule. > >> To be friendly to users, the patch also allows affected code to compile >> with -fpermissive and provides suggestions about how to fix the code: >> either declaring the desired function earlier (29131) or explicitly >> qualifying the name with this-> or Class:: (24163). > > I think that it's quite likely that there is a lot of C++ code out there > that depends on this bug to compile. So I'm glad that you've included > user guidance in the error messages, and it would be interesting to see > how much code is affected when, say, compiling a distro.
Fortunately clang already implements this rule correctly, so many code bases are already getting fixed. I personally (with a couple of other people) fixed dozens of places in boost where this was breaking code. I expect this to break huge amounts of code in g++-only code bases, but will also help improve compatibility with other compilers. I could see the temptation to introduce this as a mandatory warning for a while, and only add it under -pedantic. However, it might be easier to just force people to fix their code. Chris
