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package/gcc: fix gcc12 with uClibc

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GCC 12 produces broken binaries when used with uClibc.
E.g. `gdb` crashes on startup.

GCC HEAD fixes this in:
https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=ee4af2ed0b7322884ec4ff537564683c3749b813

Adds the commit as patch for GCC 12.

Signed-off-by: Gleb Mazovetskiy <glex.spb@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
This commit is contained in:
Gleb Mazovetskiy 2022-12-23 17:49:21 +00:00 committed by Thomas Petazzoni
parent a8807ddbe2
commit 327fab5b9d
1 changed files with 82 additions and 0 deletions
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82
package/gcc/12.2.0/0002-fix-condvar.patch Normal file
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@ -0,0 +1,82 @@
From ee4af2ed0b7322884ec4ff537564683c3749b813 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Thu, 22 Dec 2022 09:56:47 +0000
Subject: [PATCH] libstdc++: Avoid recursion in __nothrow_wait_cv::wait
[PR105730]
The commit r12-5877-g9e18a25331fa25 removed the incorrect
noexcept-specifier from std::condition_variable::wait and gave the new
symbol version @@GLIBCXX_3.4.30. It also redefined the original symbol
std::condition_variable::wait(unique_lock<mutex>&)@GLIBCXX_3.4.11 as an
alias for a new symbol, __gnu_cxx::__nothrow_wait_cv::wait, which still
has the incorrect noexcept guarantee. That __nothrow_wait_cv::wait is
just a wrapper around the real condition_variable::wait which adds
noexcept and so terminates on a __forced_unwind exception.
This doesn't work on uclibc, possibly due to a dynamic linker bug. When
__nothrow_wait_cv::wait calls the condition_variable::wait function it
binds to the alias symbol, which means it just calls itself recursively
until the stack overflows.
This change avoids the possibility of a recursive call by changing the
__nothrow_wait_cv::wait function so that instead of calling
condition_variable::wait it re-implements it. This requires accessing
the private _M_cond member of condition_variable, so we need to use the
trick of instantiating a template with the member-pointer of the private
member.
libstdc++-v3/ChangeLog:
PR libstdc++/105730
* src/c++11/compatibility-condvar.cc (__nothrow_wait_cv::wait):
Access private data member of base class and call its wait
member.
Signed-off-by: Gleb Mazovetskiy <glex.spb@gmail.com>
---
.../src/c++11/compatibility-condvar.cc | 22 ++++++++++++++++++-
1 file changed, 21 insertions(+), 1 deletion(-)
diff --git a/libstdc++-v3/src/c++11/compatibility-condvar.cc b/libstdc++-v3/src/c++11/compatibility-condvar.cc
index e3a8b8403ca..3cef3bc0714 100644
--- a/libstdc++-v3/src/c++11/compatibility-condvar.cc
+++ b/libstdc++-v3/src/c++11/compatibility-condvar.cc
@@ -67,6 +67,24 @@ _GLIBCXX_END_NAMESPACE_VERSION
&& defined(_GLIBCXX_HAVE_SYMVER_SYMBOL_RENAMING_RUNTIME_SUPPORT)
namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
{
+namespace
+{
+ // Pointer-to-member for private std::condition_variable::_M_cond member.
+ std::__condvar std::condition_variable::* __base_member;
+
+ template<std::__condvar std::condition_variable::*X>
+ struct cracker
+ { static std::__condvar std::condition_variable::* value; };
+
+ // Initializer for this static member also initializes __base_member.
+ template<std::__condvar std::condition_variable::*X>
+ std::__condvar std::condition_variable::*
+ cracker<X>::value = __base_member = X;
+
+ // Explicit instantiation is allowed to access the private member.
+ 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 +94,9 @@ __attribute__((used))
void
__nothrow_wait_cv::wait(std::unique_lock<std::mutex>& lock) noexcept
{
- this->condition_variable::wait(lock);
+ // In theory this could be simply this->std::condition_variable::wait(lock)
+ // but with uclibc that binds to the @GLIBCXX_3.4.11 symbol, see PR 105730.
+ (this->*__base_member).wait(*lock.mutex());
}
} // namespace __gnu_cxx
--
2.31.1