Request to update libc++ related packages for current Clang/LLVM toolchain

[Takashi Yano]

On Thu, 15 Jan 2026 21:53:21 +0900
Takashi Yano wrote:
> On Sun, 11 Jan 2026 23:11:00 +0200
> Florin wrote:
> > Hello Cygwin list,
> > 
> > I’ve noticed that the Clang/LLVM stable packages in Cygwin are at version
> > 20.1.x, while the libc++-devel, libc++1, libc++abi-devel, libc++abi1,
> > libunwind-devel and libunwind1 packages are still at 8.0.1. According to
> > the package summaries, they were last updated in 2019.
> > 
> > This version mismatch can present issues using modern C++ features and
> > makes it hard to use a complete LLVM toolchain with libc++ on Cygwin.
> > 
> > I searched the Cygwin mailing list archives for prior posts about updating
> > libc++, but I didn’t find a clear request or discussion about coordinating
> > libc++ versions with newer Clang.
> > 
> > Could you clarify if there is a plan to update libc++ to match more recent
> > LLVM releases, or if the recommended C++ standard library for newer and
> > future Clang versions on Cygwin should be libstdc++.
> > 
> > Thank you for your time and I'm grateful for the effort you all put into
> > this project.
> 
> I have just uploaded libcxx, compiler-rt, and libunwind packages.
> However, you cannot use them with -stdlib=libc++, -rtlib=compiler-rt,
> and -unwindlib=libunwind. This is because clang package has incomplete
> cygwin driver.
> 
> You can link them to, for example hello.cc, with:
> clang++ -stdlib=libc++ -isystem /usr/include/c++/v1 hello.cc -lc++ $(clang --print-resource-dir)/lib/cygwin/libclang_rt.builtins-x86_64.a -lunwind
> 
> The resulted a.exe will be free from libgcc_s. Please try.

I also uploaded 21.1.4-1 (Test) which works with clang/llvm 21.1.4-1 (Test).
This test version does not have the problem above.

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>