[llvm-dev] Change default config of clang on Windows

[James Y Knight via llvm-dev]

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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