hazohelet added inline comments.
================ Comment at: clang/test/Sema/warn-fortify-source.c:100-102 + __builtin_snprintf(buf, 2, "%#x", n); + __builtin_snprintf(buf, 2, "%#X", n); + __builtin_snprintf(buf, 2, "%#o", n); ---------------- nickdesaulniers wrote: > Note that GCC -Wformat-truncation can warn on some of these. > > https://godbolt.org/z/jE3axWe1W > > Looks like the diagnostic keeps an up and lower bounds on the estimated > format string expansion. > > Trunk for Clang also warns for these, so is this change a regression? Or are > both GCC and Clang (trunk) incorrect? Clang trunk is saying something factually incorrect because it says the output `will always be truncated`, when in fact `__builtin_snprintf(buf, 2, "%#x", n);` doesn't trigger truncation if `n` is zero. GCC is correct but is more conservative than clang's `ALWAYS be truncated` diagnostics. GCC's warning message is `... directive output MAY BE truncated` . GCC doesn't warn on it when `n` is known to be zero. (https://godbolt.org/z/E51a3Pfhr) GCC's behavior makes sense here because the truncation does happen whenever `n` is not zero. If the user knows `n` is zero then they have no reason to use `%#x` specifier. So, I think it makes sense to assume `n` is not zero and emit diagnostics, but it definitely needs diagnostics rewording like `is likely to be truncated`. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D159138/new/ https://reviews.llvm.org/D159138 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
