Re: [Buildroot] [PATCH] package/gcc: fix gcc12 with uClibc

[Andreas Ziegler <br015@umbiko.net>]

Fixes a recursive call to __nothrow_wait_cv::wait() in 
libstdc++-v3/src/c++11/compatibility-condvar.cc which occurs whenever a 
C++ application (gcc12 +uClibc) calls std::condition_variable::wait()

Also observed with: mpd using liburing.

Tested-by: Andreas Ziegler <br015@umbiko.net>

On 2022-12-21 12:52, Gleb Mazovetskiy <glex.spb@gmail.com> wrote:
> GCC 12 produces broken binaries when used with uClibc.
> E.g. `gdb` crashes on startup.
> 
> This adds a patch to address the issue.
> The patch is from:
> 
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105730#c8
> 
> Signed-off-by: Gleb Mazovetskiy <glex.spb@gmail.com>
> ---
>  .../gcc/12.2.0/0002-fix-condvar-compat.patch  | 33 +++++++++++++++++++
>  1 file changed, 33 insertions(+)
>  create mode 100644 package/gcc/12.2.0/0002-fix-condvar-compat.patch
> 
> diff --git a/package/gcc/12.2.0/0002-fix-condvar-compat.patch 
> b/package/gcc/12.2.0/0002-fix-condvar-compat.patch
> new file mode 100644
> index 0000000000..9bbd481dbe
> --- /dev/null
> +++ b/package/gcc/12.2.0/0002-fix-condvar-compat.patch
> @@ -0,0 +1,33 @@
> +--- a/libstdc++-v3/src/c++11/compatibility-condvar.cc
> ++++ b/libstdc++-v3/src/c++11/compatibility-condvar.cc
> +@@ -67,6 +67,22 @@ _GLIBCXX_END_NAMESPACE_VERSION
> +     && defined(_GLIBCXX_HAVE_SYMVER_SYMBOL_RENAMING_RUNTIME_SUPPORT)
> + namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
> + {
> ++namespace
> ++{
> ++  std::__condvar std::condition_variable::* __base_member;
> ++
> ++  template<std::__condvar std::condition_variable::*X>
> ++    struct cracker
> ++    {
> ++      static std::__condvar std::condition_variable::* value;
> ++    };
> ++  template<std::__condvar std::condition_variable::*X>
> ++    std::__condvar std::condition_variable::*
> ++      cracker<X>::value = __base_member = X;
> ++
> ++  template class cracker<&std::condition_variable::_M_cond>;
> ++}
> ++
> + struct __nothrow_wait_cv : std::condition_variable
> + {
> +   void wait(std::unique_lock<std::mutex>&) noexcept;
> +@@ -76,7 +92,7 @@ __attribute__((used))
> + void
> + __nothrow_wait_cv::wait(std::unique_lock<std::mutex>& lock) noexcept
> + {
> +-  this->condition_variable::wait(lock);
> ++  (this->*__base_member).wait(*lock.mutex());
> + }
> + } // namespace __gnu_cxx
> --
> 2.37.2
> 
> 
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