On Tue, Jan 08, 2008 at 11:28:22PM +0200, Ismail Dönmez wrote: > Hi all, > > Looks like gcc 4.3 has some rather inconvenient changes in C++ FE, with the > latest trunk. Lets see with an example : > > [~]> cat test.cpp > #define foo bar > #define foo baz > > [~]> g++ -c test.cpp > test.cpp:2:1: error: "foo" redefined > test.cpp:1:1: error: this is the location of the previous definition > > I don't know the reasoning behind this change but this breaks many C++ > programs unless -fpermissive is used. Why? Because everybody loves to install > their own config.h (Python, libmp4v2 being nice examples) which just > carelessly #define anything its asked for with ifndef ... endif . > > Now flash back to real world: this breaks any C++ application that uses > Python, libmp4v2, libjpeg and possibly many others. And I think this is a > real bad behaviour change and I am not sure if its worth all the trouble.
There's certainly an argument that this change is ill-advised. However, your statements in the last paragraph aren't true: most quality open source projects have a "no warnings" rule (or at least try to eliminate warnings), and most programmers know about #undef. Since people have already built whole distros with the gcc from the trunk, clearly they are managing to build C++ applications that use Python, libmp4v2, libjpeg etc.
