[gcc r15-7645] libstdc++: Use init_priority attribute for tzdb globals [PR118811]

[Jonathan Wakely via Libstdc++-cvs]

https://gcc.gnu.org/g:99f57446e63b8ebeaeeae8dc48981cd5f1dfb831

commit r15-7645-g99f57446e63b8ebeaeeae8dc48981cd5f1dfb831
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Wed Feb 12 17:29:59 2025 +0000

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

Diff:
---
 libstdc++-v3/src/c++20/tzdb.cc                     | 11 ++++++----
 .../testsuite/std/time/tzdb_list/pr118811.cc       | 25 ++++++++++++++++++++++
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/libstdc++-v3/src/c++20/tzdb.cc b/libstdc++-v3/src/c++20/tzdb.cc
index 7e8cce7ce8cf..c3bb6a12ccc1 100644
--- a/libstdc++-v3/src/c++20/tzdb.cc
+++ b/libstdc++-v3/src/c++20/tzdb.cc
@@ -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
 
diff --git a/libstdc++-v3/testsuite/std/time/tzdb_list/pr118811.cc 
b/libstdc++-v3/testsuite/std/time/tzdb_list/pr118811.cc
new file mode 100644
index 000000000000..3968be3f0eca
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/tzdb_list/pr118811.cc
@@ -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()
+{
+}