qiucf added a comment. Hi,
> Why is --overlay-platform-toolchain added instead of using -isystem and -L? > > The functionality overlaps with -B. Unsure why introduce a new mechanism. We may want to use an extra toolchain like the Advance Toolchain (https://github.com/advancetoolchain/advance-toolchain) which includes Glibc/GCC/GDB/LD/etc. but is not a complete OS distribution. So we should not simply change `sysroot` here. Using `-isystem` and `-L` is okay in principle, but (1) it breaks expected include order (`-isystem` just inserts it in the top); (2) we have to manually insert many `-isystem` paths; (3) we want to reuse the logic in clang driver code. `-B` changes search path of crt runtime files, but include/library/dynamic linker paths are the same. What this option does is to insert the extra toolchain in all search paths but with higher priority than system default. ================ Comment at: clang/include/clang/Driver/Options.td:4184 +def _overlay_platform_toolchain_EQ : Joined<["--"], "overlay-platform-toolchain=">; +def _overlay_platform_toolchain : Separate<["--"], "overlay-platform-toolchain">, Alias<_overlay_platform_toolchain_EQ>; def _param : Separate<["--"], "param">, Group<CompileOnly_Group>; ---------------- MaskRay wrote: > Separate-form driver options are not conventional. New driver options should > just avoid them. Thanks for the reminder! ================ Comment at: clang/lib/Driver/ToolChains/Gnu.cpp:1870 + if (const Arg *X = Args.getLastArg( + clang::driver::options::OPT__overlay_platform_toolchain_EQ)) ---------------- MaskRay wrote: > Why was this rule added? Linker and other paths relies on location of specified GCC toolchain. And the toolchain specified by `overlay-platform-toolchain` is expected to have GCC installation included. But for sure, it has lower priority than `gcc-toolchain`. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D121992/new/ https://reviews.llvm.org/D121992 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
