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libstdc++: Use init_priority attribute for tzdb globals [PR118811]

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When linking statically to libstdc++.a (or to libstdc++_nonshared.a in
the RHEL devtoolset compiler) there's a static initialization order
problem where user code might be constructed before the
std::chrono::tzdb_list globals, and so might try to use them after
they've already been destroyed.

Use the init_priority attribute on those globals so that they are
initialized early. Since r15-7511-g4e7f74225116e7 we can disable the
warnings for using a reserved priority using a diagnostic pragma.

libstdc++-v3/ChangeLog:

	PR libstdc++/118811
	* src/c++20/tzdb.cc (tzdb_list::_Node): Use init_priority
	attribute on static data members.
	* testsuite/std/time/tzdb_list/pr118811.cc: New test.
This commit is contained in:
Jonathan Wakely 2025-02-12 17:29:59 +00:00 • committed by Jonathan Wakely
parent d324467544
commit 99f57446e6
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2 changed files with 32 additions and 4 deletions
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11
libstdc++-v3/src/c++20/tzdb.cc
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@ -133,6 +133,8 @@ namespace std::chrono
// of this type gives them access to the private members of time_zone
// and tzdb, without needing them declared in the <chrono> header.
// The tzdb_list singleton. This doesn't contain the actual linked list,
// but it has member functions that give access to it.
static tzdb_list _S_the_list;
#if USE_ATOMIC_SHARED_PTR
@ -177,15 +179,16 @@ namespace std::chrono
// Implementation of the private constructor used for the singleton object.
constexpr tzdb_list::tzdb_list(nullptr_t) { }
// The tzdb_list singleton. This doesn't contain the actual linked list,
// but it has member functions that give access to it.
#pragma GCC diagnostic ignored "-Wprio-ctor-dtor"
[[gnu::init_priority(99)]]
constinit tzdb_list tzdb_list::_Node::_S_the_list(nullptr);
// Shared pointer to the first Node in the list.
[[gnu::init_priority(99)]]
constinit tzdb_list::_Node::head_ptr tzdb_list::_Node::_S_head_owner{nullptr};
#if USE_ATOMIC_LIST_HEAD
// Lock-free access to the first Node in the list.
[[gnu::init_priority(99)]]
constinit atomic<tzdb_list::_Node*> tzdb_list::_Node::_S_head_cache{nullptr};
#endif

25
libstdc++-v3/testsuite/std/time/tzdb_list/pr118811.cc Normal file
View file

@ -0,0 +1,25 @@
// { dg-do run { target c++20 } }
// { dg-require-effective-target tzdb }
// { dg-require-effective-target cxx11_abi }
// { dg-require-static-libstdcxx }
// { dg-additional-options "-static-libstdc++" }
#include <chrono>
struct Global
{
Global()
{
(void) std::chrono::current_zone(); // initialize tzdb on first use
}
~Global()
{
(void) std::chrono::current_zone(); // attempt to use it again on exit
}
} global;
int main()
{
}