> > Short story: > > To make delta debugging more useful, gcc's STL system headers should > > all compile without warnings at the highest error checking level > > without the use of hardcoded warning suppressions in the compiler > > based on whether the code is in a system header or not (see > > http://gcc.gnu.org/ml/gcc-patches/2005-07/msg00049.html for an example > > of such a suppression). > > How bad is it? Can you compile all the headers with -Wsystem-headers > and -W -Wall and see how many problems there are? >
This isn't sufficent, as unless the templates are actually getting instansiated then there won't be any warnings produced. Some errors are only produced for very specific headers (for example, bitset will produce an error about unused variables only in the case of bitset<0>, which is valid but I'd imagine never actually used). There appears to be a bug whereby headers in "bits/" in libstdc++ (which is where most of the actual code is) appear uneffected by using Wsystem-headers, so in actual fact the headers are probably already fairly clean. The best way to make, and keep, the headers clean would probably be to make the libstdc++ testsuite run at a higher warning level by default. If you do this now you'll find a lot of tests fail, but the vast majority appear to be from problems in the headers used only in the testsuite. I'd hoped to tackle this, but don't have enough time at the moment. I don't imagine it would be too hard in most cases. Some warnings, for example -Weffc++, as shown in PR14172 currently cause problems with the libstdc++ headers, but fixing them would require pessimising or complicating code.
