On 08/01/2008, Ismail Dönmez <[EMAIL PROTECTED]> wrote: > Tuesday 08 January 2008 23:34:13 tarihinde Joe Buck şunları yazmıştı: > > > Since people have already built whole distros with the gcc from the trunk, > > clearly theyare managing to build C++ applications that use > > Python,libmp4v2, libjpeg etc. > > Yes true because they use -fpermissive which will let this error into a > warning, which also suggests this change is not good. >
Hi Ismail, I implemented the change as the fix to a bug that was reported by fellow (and more senior) GCC developers. Let me try to explain (although, I hoped that it will be fairly clear from gcc.gnu.org/gcc-4.3/changes.html). We have a series of diagnostics that are important or required by the standard (or both). Those are called pedwarns. It is an unfortunate name for two reasons: 1) Not all pedwarns are enabled by -pedantic, some are enabled by default; and 2) pedwarns can be either warnings or errors, and what they are depends on command-line options and the default of each front-end. In fact, pedwarnss are warnings by default in the C front-end. But they are errors by default in the C++ front-end unless you use -fpermissive so they are downgraded to warnings. Before GCC 4.3, the C++ preprocessor was ignoring the default of the C++ front-end. In fact, there was an inconsistence between the settings of the C++ preprocessor and the settings of the C++ front-end. It worked for a few things (-pedantic-errors worked fine), but not for others (the default settings and the effect of -fpermissive). The inconsistency was evident in the code and if you played with combinations of -pedantic-errors and -fpermissive. I hope you see. It is not that we decided that some warnings should actually be errors. It is that those warnings belong to a group of diagnostics that were supposed to be errors by default. Of course, we can discuss whether those warnings (or a particular one) should be enabled by default, or whether they (or a particular one of them) should belong to that group of diagnostics (pedwarns) or whether pedwarns should be errors by default in C++ front-end. I was hoping those discussions would arise but it didn't happen. It seems people just used -fpermissive or fixed the warning. For your particular example, you could open a regression bug against 4.3 that says: * '"foo' redefined" is not mandated by the standard or it is not serious enough, so it should not be a pedwarn just a normal warning; or * "'foo' redefined", although mandated by the standard, is a nuisance and irrelevant, it should only be active when -pedantic is given and not by default. The fixes to those are one-liners once the correct decision is made. I volunteer (in fact, I have volunteered repeatedly) to implement, test and commit the changes needed. But I don't consider that I have the expertise to make the correct decision. But reverting my patch is just a quick hack that won't fix anything for long, since in the future the preprocessor will probably use the same diagnostic machinery that the front-ends, making impossible the inconsistency described above and, thus, bringing up this whole issue again. I hope I have been clear in my explanation. Cheers, Manuel.
