diff --git a/libcxx/include/__configuration/availability.h b/libcxx/include/__configuration/availability.h
index ae58e36b508b4..19dce7d9c8c8e 100644
--- a/libcxx/include/__configuration/availability.h
+++ b/libcxx/include/__configuration/availability.h
@@ -355,6 +355,12 @@
 #define _LIBCPP_AVAILABILITY_HAS_BAD_FUNCTION_CALL_GOOD_WHAT_MESSAGE _LIBCPP_INTRODUCED_IN_LLVM_21
 // No attribute, since we've had bad_function_call::what() in the headers before
 
+// This controls whether we assume that __shared_mutex_base::~__shared_mutex_base() is defined in the dylib.
+// Defining that function in the dylib provides additional flexibility for changing the representation of the
+// class, which may eventually be used to provide a better implementation.
+#define _LIBCPP_AVAILABILITY_HAS_SHARED_MUTEX_BASE_DESTRUCTOR _LIBCPP_INTRODUCED_IN_LLVM_21
+// No attribute, since we define the destructor in the headers otherwise
+
 // Define availability attributes that depend on both
 // _LIBCPP_HAS_EXCEPTIONS and _LIBCPP_HAS_RTTI.
 #if !_LIBCPP_HAS_EXCEPTIONS || !_LIBCPP_HAS_RTTI
diff --git a/libcxx/include/shared_mutex b/libcxx/include/shared_mutex
index 8c02e348e4de7..f8836d46e9a43 100644
--- a/libcxx/include/shared_mutex
+++ b/libcxx/include/shared_mutex
@@ -163,7 +163,11 @@ struct _LIBCPP_EXPORTED_FROM_ABI __shared_mutex_base {
   static const unsigned __n_readers_     = ~__write_entered_;
 
   __shared_mutex_base();
+#      if defined(_LIBCPP_BUILDING_LIBRARY) || _LIBCPP_AVAILABILITY_HAS_SHARED_MUTEX_BASE_DESTRUCTOR
+  ~__shared_mutex_base();
+#      else
   _LIBCPP_HIDE_FROM_ABI ~__shared_mutex_base() = default;
+#      endif
 
   __shared_mutex_base(const __shared_mutex_base&)            = delete;
   __shared_mutex_base& operator=(const __shared_mutex_base&) = delete;
diff --git a/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist
index 162757c7e37ec..b14921aebfe49 100644
--- a/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist
+++ b/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -1551,6 +1551,8 @@
 {'is_defined': True, 'name': '__ZNSt3__119__shared_mutex_base8try_lockEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__119__shared_mutex_baseC1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__119__shared_mutex_baseC2Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__119__shared_mutex_baseD1Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__119__shared_mutex_baseD2Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__119__shared_weak_count10__add_weakEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__119__shared_weak_count12__add_sharedEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__119__shared_weak_count14__release_weakEv', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/i686-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/i686-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist
index 4b6f3548ce495..189314de51ffc 100644
--- a/libcxx/lib/abi/i686-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist
+++ b/libcxx/lib/abi/i686-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -1187,6 +1187,8 @@
 {'is_defined': True, 'name': '_ZNSt6__ndk119__shared_mutex_base8try_lockEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk119__shared_mutex_baseC1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk119__shared_mutex_baseC2Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt6__ndk119__shared_mutex_baseD1Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt6__ndk119__shared_mutex_baseD2Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk119__shared_weak_count10__add_weakEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk119__shared_weak_count12__add_sharedEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk119__shared_weak_count14__release_weakEv', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/powerpc-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/powerpc-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist
index 2b85596bd87f6..cd58901779433 100644
--- a/libcxx/lib/abi/powerpc-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist
+++ b/libcxx/lib/abi/powerpc-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -545,6 +545,8 @@
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_base8try_lockEv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseC1Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseC2Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
+{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseD1Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
+{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseD2Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_weak_count14__release_weakEv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_weak_count4lockEv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_weak_countD0Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/powerpc64-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/powerpc64-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist
index 6ebdab96ed455..f55df888a0a29 100644
--- a/libcxx/lib/abi/powerpc64-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist
+++ b/libcxx/lib/abi/powerpc64-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -545,6 +545,8 @@
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_base8try_lockEv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseC1Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseC2Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
+{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseD1Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
+{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseD2Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_weak_count14__release_weakEv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_weak_count4lockEv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__119__shared_weak_countD0Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist
index f6f7d7fd8265a..38221d575eea0 100644
--- a/libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist
+++ b/libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -1550,6 +1550,8 @@
 {'is_defined': True, 'name': '__ZNSt3__119__shared_mutex_base8try_lockEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__119__shared_mutex_baseC1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__119__shared_mutex_baseC2Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__119__shared_mutex_baseD1Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__119__shared_mutex_baseD2Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__119__shared_weak_count10__add_weakEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__119__shared_weak_count12__add_sharedEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__119__shared_weak_count14__release_weakEv', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/x86_64-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/x86_64-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist
index 45f3d7c5904e8..a7106d9102385 100644
--- a/libcxx/lib/abi/x86_64-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist
+++ b/libcxx/lib/abi/x86_64-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -1187,6 +1187,8 @@
 {'is_defined': True, 'name': '_ZNSt6__ndk119__shared_mutex_base8try_lockEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk119__shared_mutex_baseC1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk119__shared_mutex_baseC2Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt6__ndk119__shared_mutex_baseD1Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt6__ndk119__shared_mutex_baseD2Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk119__shared_weak_count10__add_weakEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk119__shared_weak_count12__add_sharedEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk119__shared_weak_count14__release_weakEv', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/x86_64-unknown-freebsd.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/x86_64-unknown-freebsd.libcxxabi.v1.stable.exceptions.nonew.abilist
index de8cf6deef1df..88acfbda37c6d 100644
--- a/libcxx/lib/abi/x86_64-unknown-freebsd.libcxxabi.v1.stable.exceptions.nonew.abilist
+++ b/libcxx/lib/abi/x86_64-unknown-freebsd.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -1201,6 +1201,8 @@
 {'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_base8try_lockEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseC1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseC2Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseD1Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseD2Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__119__shared_weak_count10__add_weakEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__119__shared_weak_count12__add_sharedEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__119__shared_weak_count14__release_weakEv', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.nonew.abilist
index 8c55c4385f6f6..30618108ee8b7 100644
--- a/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.nonew.abilist
+++ b/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -1199,6 +1199,8 @@
 {'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_base8try_lockEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseC1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseC2Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseD1Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseD2Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__119__shared_weak_count10__add_weakEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__119__shared_weak_count12__add_sharedEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__119__shared_weak_count14__release_weakEv', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.noexceptions.nonew.abilist b/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.noexceptions.nonew.abilist
index 51caa07a74330..58d4ed765ab92 100644
--- a/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.noexceptions.nonew.abilist
+++ b/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.noexceptions.nonew.abilist
@@ -1170,6 +1170,8 @@
 {'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_base8try_lockEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseC1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseC2Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseD1Ev', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__119__shared_mutex_baseD2Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__119__shared_weak_count10__add_weakEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__119__shared_weak_count12__add_sharedEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__119__shared_weak_count14__release_weakEv', 'type': 'FUNC'}
diff --git a/libcxx/src/shared_mutex.cpp b/libcxx/src/shared_mutex.cpp
index 6180833736956..27ef9d351966d 100644
--- a/libcxx/src/shared_mutex.cpp
+++ b/libcxx/src/shared_mutex.cpp
@@ -16,6 +16,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 // Shared Mutex Base
 __shared_mutex_base::__shared_mutex_base() : __state_(0) {}
+__shared_mutex_base::~__shared_mutex_base() {}
 
 // Exclusive ownership