MaskRay added inline comments.
================ Comment at: clang/CMakeLists.txt:179-183 +if(DEFAULT_SYSROOT) + message(WARNING "DEFAULT_SYSROOT is deprecated and will be removed. Use " + "configuration files (https://clang.llvm.org/docs/UsersManual.html#configuration-files)" + "to specify the default --sysroot=") +endif() ---------------- bcain wrote: > MaskRay wrote: > > MaskRay wrote: > > > bcain wrote: > > > > MaskRay wrote: > > > > > bcain wrote: > > > > > > At one time I believe that the clang configuration files could not > > > > > > specify paths relative to the clang executable. AFAICT > > > > > > `DEFAULT_SYSROOT` does support this. > > > > > > > > > > > > But if I'm mistaken about that can we add an example to the docs at > > > > > > https://clang.llvm.org/docs/UsersManual.html#configuration-files > > > > > > illustrating how to use a relative sysroot? > > > > > Clang configuration files just complement user-specified command line > > > > > options. As one can do `--sysroot=./sysroot`, one can add > > > > > `--sysroot=./sysroot` to a configuration file, too. > > > > > > > > > > If you think having a sysroot example is useful, I can add > > > > > > > > > > ``` > > > > > # Relative --sysroot > > > > > --sysroot=./sysroot > > > > > ``` > > > > > before > > > > > clang/docs/UsersManual.rst:1018 `-c --target=x86_64-unknown-linux-gnu` > > > > IIUC: when clang takes a `--sysroot=./sysroot` argument, it will > > > > interpret that path as a prefix to the files it wants to access. So > > > > the system will treat it as relative to the environment's `cwd`, > > > > correct? > > > > > > > > But when `DEFAULT_SYSROOT` is set to a relative path, that relative > > > > path is considered to be relative to `clang`. Therefore a convenient > > > > feature that we take advantage of is setting it to something like > > > > `../target/hexagon-unknown-linux-musl` in order to have anyone who > > > > invokes `hexagon-unknown-linux-clang` from any path be able to find the > > > > includes and libraries distributed with the toolchain without having to > > > > specify the sysroot. > > > > > > > > Maybe there's a better way to achieve this without the need for a > > > > relative `DEFAULT_SYSROOT` but it's been very useful and the config > > > > files do not seem suited to replace it. > > > `--sysroot=` is used as a prefix to certain files, primarily libc and GCC > > > installations. > > > > > > `-DDEFAULT_SYSROOT=...` just changes `clang/lib/Driver/Driver.cpp:203` > > > `SysRoot(DEFAULT_SYSROOT)`. > > > There is no magic related to the `clang` executable path. CMake doesn't > > > do any magic, either. > > Ah, sorry. There is magic: D76653 (@sbc100). > > Ah, sorry. There is magic: D76653 (@sbc100). > > Okay, so should we abandon the plan to deprecate `DEFAULT_SYSROOT`? Or could > we add a corresponding feature to config files if we want to get rid of it? The way relative `DEFAULT_SYSROOT` looks strange to me as it is not exactly equivalent to user-specified `--sysroot=`. I hope that there is a way to achieve @sbc100's goal. I think a proper mechanism will take time, and we probably can just deprecated `GCC_INSTALL_PREFIX` for now. And I wish that RHEL/CentOS can migrate to a modern practice. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D158218/new/ https://reviews.llvm.org/D158218 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
