[PATCH] D141206: [clang] [MinGW] Avoid adding <base>/include and <base>/lib when cross compiling

[Martin Storsjö via Phabricator via cfe-commits]

mstorsjo added a comment.

In D141206#4037160 <https://reviews.llvm.org/D141206#4037160>, @alvinhochun wrote:

> The idea sounds reasonable. I don't know mingw-w64 toolchains well enough, but I'll try:
>
> How does it interact with the following conditions (lines 469-475)? They look like they may be looking for a mingw-w64 sysroot, which may be ignored by the new check.
>
>   else if (llvm::ErrorOr<std::string> TargetSubdir = findClangRelativeSysroot(
>                getDriver(), LiteralTriple, getTriple(), SubdirName))
>     Base = std::string(llvm::sys::path::parent_path(TargetSubdir.get()));
>   else if (llvm::ErrorOr<std::string> GPPName =
>                findGcc(LiteralTriple, getTriple()))
>     Base = std::string(llvm::sys::path::parent_path(
>         llvm::sys::path::parent_path(GPPName.get())));

Thanks for having a look!

Those cases are taken into account here; for the case of `findClangRelativeSysroot`, if clang is executing in e.g. `<somewhere>/llvm-mingw/bin/clang` and it finds `<somewhere>/llvm-mingw/x86_64-w64-mingw32`, then it doesn't pick that as `<base>`, but it picks `<somewhere>/llvm-mingw`, and gets the `x86_64-w64-mingw32` subdir prefix included via the `SubdirName` variable.

Likewise, if `findClangRelativeSysroot` failed, but `findGcc` found `/usr/bin/x86_64-w64-mingw32-gcc` in `$PATH`, then it also picks `/usr` as `<base>` (which is needed for finding libgcc things under `<base>/lib/gcc`).

So for these reasons, the search can't stay entirely within `<base>/<target triple>` - and we may want to skip `<base>/include` and `<base>/lib` when we believe that's meant for a different target.


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