>> But hopefully slightly less self serving. > > To be honest, it doesn't seem an unfair characterization to me. > > GCC could highlight the ethical and tit-for-tat benefits of the GPL, but I > guess they do not see those as a benefit. > > GCC has also the benefit of being a more mature code base and, as a result, > it has been more thoroughly tested in a wider range of codes; yet this is > difficult to quantify and arguably Clang is more widely used today than GCC, > just not in Linux, thus this might not be true anymore. GCC does a much better job of optimizing. I run benchmarks for some libraries regularly to ensure there are no regressions. GCC is consistently 2x faster than Clang, and GCC is on-par with ICC. It seems the slow-down is the treatment of const-expr's. Under the laws of the physical universe as we know them, some values are fixed at compile time won't change (regardless of their const-expr status). GCC optimizes them (common sense), while Clang does not (expected to somehow change). That little slow down adds up, and it makes us do things like avoid std::numeric_limits<T>::max() in favor of a #define instead. More complex examples include propagating a constant using a template parameter instead of a function parameter. GCC will realize a constant does not change under the laws of the physical universe as we know them; while Clang will treat the constant passed as a parameter as something that can miraculously change after saving the source file. Jeff
