rjmccall added a comment. In D124435#3701163 <https://reviews.llvm.org/D124435#3701163>, @jyknight wrote:
> In D124435#3697259 <https://reviews.llvm.org/D124435#3697259>, @rjmccall > wrote: > >> I know what you're saying, but I don't think it matches any model of how >> programmers use command line flags. You're imagining that a programmer sits >> down and considers all of their flags deeply and holistically before >> touching any of them, and that's just not how these things go in actual >> build systems. Flags have a tendency to be set in separate places and >> therefore to drift. Someone setting this option is doing it because they >> have a concrete compatibility need, and the flag going from meaning "be >> compatible with GCC" to meaning "be compatible with old Clangs" based on the >> value of a separate flag is surprising and likely to cause bugs. > > Funny, my argument is based precisely on the fact that people _don't_ > understand deeply what things are doing, and that the original proposal is > likely to trigger bugs via mistakes in its usage! > > The default (`-mconservative-small-integer-abi`) is "be compatible with all > Clang and GCC versions" -- it "just works". (I think everyone agrees upon > that being the default.) > > So, the use-case for `-mconservative-small-integer-abi` is not a need for > compatibility but rather a need for performance/code-size overriding > cross-compiler compatibility concerns. In that case, the user better be able > to answer "what other compiler/version do you need to be compatible with, if > any?" -- and set -fclang-abi-compat flag appropriately based on that answer. > > That seems much easier thing to explain to a user than the details of where > exactly extension may/must happen in the call ABI. I'm not arguing that we shouldn't work `-fclang-abi-compat` into this; I think that is a very good idea. And for many people, that'll be all they need. My concern is about the people who do add `-mno-conservative-small-integer-abi` to their builds. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D124435/new/ https://reviews.llvm.org/D124435 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
