Safe to link to static libstdc++ from shared library?

[Jonathan Wakely]

On Fri, 14 Nov 2025 at 13:45, Fredrik Orderud <forderud@gmail.com> wrote:
>
> I'm working on a project developing a Linux shared library (.so) with
> a pure "C" interface that we want to be as widely compatible as
> possible with multiple distros of various age. The -static-libstdc++
> option therefore seemed attractive, since it appear to eliminate
> run-time dependencies to libstdc++. We've therefore used
> -static-libstdc++ together with -Wl,--exclude-libs,ALL in an attempt
> to encapsulate all C++ dependencies (and other 3rd party libraries),
> so that callers doesn't need to know about the C++ stuff inside the
> shared library.
>
> This worked fine for a while, but now we suddenly started experiencing
> segmentation faults when calling std::async from the shared lib. I'm
> not sure if this is a caused by a bug, a known limitation or our
> misunderstanding of the libstdc++ documentation. A minimal reproducer
> is available on
> https://github.com/forderud/UnixSharedLib/tree/main/static-libstdc%2B%2B
>
> ASK: Are there any documented or undocumented limitations on
> -static-libstdc++ usage when building shared libraries on Linux?

The problem is your use of --exclude-libs - that won't work.

You can't pretend there are no dependencies on the C++ runtime like
that, the symbols in libstdc++ need to be globally visible so that the
linker can properly resolve them across different ELF objects.