[llvm-dev] Change default config of clang on Windows (original) (raw)

James Y Knight via llvm-dev llvm-dev at lists.llvm.org
Thu Feb 27 14:26:15 PST 2020

We have that already. https://releases.llvm.org/6.0.0/tools/clang/docs/UsersManual.html#configuration-files

On Thu, Feb 27, 2020 at 5:15 PM Fangrui Song via llvm-dev < llvm-dev at lists.llvm.org> wrote:

On 2020-02-26, Reid Kleckner via llvm-dev wrote: >I think "legacy" is the answer to most of your questions. > >1. I think clang still uses ld by default, so clang-cl is similar. Besides, >every build system we encountered migrating from MSVC calls link >directly, and needed to be updated to call lld-link. > >2. I think we should probably configure lld to find the clang resource >directory. At the very least, clang-cl -fuse-ld=lld should add it. > >3. I think this is because there is no clang spelling for the /MD & /MT >flags, so we have to pick some CRT so that hello world links. You can work >around it with -nodefaultlib and passing your own. > >4. That's true, but that's been the case for every build system we've >encountered. > >So, I think there is room for improvement and better defaults. > >Most options in clang are controlled by flags, not configure-time cmake >options. From the clang developer perspective, this is good, clang is >always a cross compiler and can do anything anywhere at runtime. But from a >user or packager perspective, this is often painful. Users often write >compiler wrapper scripts to fill in their preferred default options: >default target, default include paths, default library paths, etc. > >On Sun, Feb 23, 2020 at 12:37 PM Максим Власов via llvm-dev <_ _>llvm-dev at lists.llvm.org> wrote: > >> I'm getting trouble using clang with compiled libc++ on MSVC. >> 1. why clang chooses link over lld-link by default? I don't really >> wish to write -fuse-ld=lld-link every single time I build something. >> 2. why lld-link doesn't search inside default lib directory? I need to >> manually show him where it is although I put that binary in <LLVM_ _>> root>\lib\ >> 3. why clang invokes linker with -defaultlib:libcmt? I mean libc++ build >> guide under MSVC produces -MD version of either libc++.lib or c++.lib >> 4. Since (3), it's not possible to build anything without splitting >> compiler and linker calls - clang by default produces -MT versions of >> objects and linker fails to compose it with -MD library. No, -dynamic >> flag does not help either. >> Any fixes to these? Can I config clang somehow except --config option?

May I rephrase the question as asking about the feasibility of GCC -specs= ? https://gcc.gnu.org/onlinedocs/gcc/Spec-Files.html

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