libcxx: std::ostream::sentry should be exported

.github/workflows/libcxx-build-and-test.yaml

@@ -44,6 +44,7 @@ jobs:
       matrix:
         config: [
           'frozen-cxx03-headers',
+          'generic-abi-unstable',
           'generic-cxx03',
           'generic-cxx26',
           'generic-modules'
@@ -54,6 +55,9 @@ jobs:
           - config: 'generic-gcc'
             cc: 'gcc-14'
             cxx: 'g++-14'
+          - config: 'generic-gcc-abi-unstable'
+            cc: 'gcc-14'
+            cxx: 'g++-14'
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - name: ${{ matrix.config }}.${{ matrix.cxx }}
@@ -239,7 +243,7 @@ jobs:
 
   windows:
     runs-on: windows-2022
-    needs: [ stage2 ]
+    #needs: [ stage2 ]
     strategy:
       fail-fast: false
       matrix:
@@ -263,10 +267,24 @@ jobs:
         if: ${{ matrix.mingw != true }}
         run: |
           choco install -y llvm --version=19.1.7 --allow-downgrade
+      - name: Download test llvm-mingw
+        if: ${{ matrix.mingw == true }}
+        shell: bash
+        run: |
+          ARTIFACT_URL=https://github.com/jeremyd2019/llvm-mingw/actions/runs/15080594305/artifacts/3143907630
+          case "$ARTIFACT_URL" in
+          https://github.com/*/actions/runs/[0-9]*/artifacts/[0-9]*)
+            ARTIFACT_URL="$(echo "$ARTIFACT_URL" |
+              sed 's|^\(https://\)\(github.com/\)\(.*/actions/\)runs/[0-9]*/\(artifacts/[0-9]*\)$|\1api.\2repos/\3\4/zip|')"
+              ;;
+          esac
+          curl -H "Authorization: token ${{secrets.GITHUB_TOKEN}}" \
+              -fLo artifact.zip "$ARTIFACT_URL"
+          powershell Expand-Archive artifact.zip -DestinationPath .
+          rm -f artifact.zip
       - name: Install llvm-mingw
         if: ${{ matrix.mingw == true }}
         run: |
-          curl -LO https://github.com/mstorsjo/llvm-mingw/releases/download/20250114/llvm-mingw-20250114-ucrt-x86_64.zip
           powershell Expand-Archive llvm-mingw*.zip -DestinationPath .
           del llvm-mingw*.zip
           mv llvm-mingw* c:\llvm-mingw

clang/lib/Sema/SemaTemplateInstantiate.cpp

@@ -4247,6 +4247,7 @@ Sema::InstantiateClassMembers(SourceLocation PointOfInstantiation,
         continue;
 
       if (Context.getTargetInfo().getTriple().isOSWindows() &&
+          !Context.getTargetInfo().getTriple().isOSCygMing() &&
           TSK == TSK_ExplicitInstantiationDeclaration) {
         // On Windows, explicit instantiation decl of the outer class doesn't
         // affect the inner class. Typically extern template declarations are

clang/test/CodeGenCXX/mingw-template-dllexport.cpp

@@ -6,46 +6,121 @@
 #define JOIN2(x, y) x##y
 #define JOIN(x, y) JOIN2(x, y)
 #define UNIQ(name) JOIN(name, __LINE__)
-#define USEMEMFUNC(class, func) void (class::*UNIQ(use)())() { return &class::func; }
+#define USEMEMFUNC(class, func) auto UNIQ(use) = &class::func;
 
 template <class T>
 class c {
+  // MinGW-GCC does not apply 'dllexport' to inline member function in dll-exported template but clang does from long ago.
   void f() {}
+  void g();
+  inline static int u = 0;
+  static int v;
 };
+template <class T> void c<T>::g() {}
+template <class T> int c<T>::v = 0;
 
+// #1
 template class __declspec(dllexport) c<int>;
 
-// CHECK: define {{.*}} dllexport {{.*}} @_ZN1cIiE1fEv
-
+// #2
 extern template class __declspec(dllexport) c<char>;
 template class c<char>;
 
-// CHECK: define {{.*}} dllexport {{.*}} @_ZN1cIcE1fEv
-
+// #3
 extern template class c<double>;
-template class __declspec(dllexport) c<double>;
+template class __declspec(dllexport) c<double>; // expected-warning {{ 'dllexport' attribute ignored on explicit instantiation definition }}
 
-// CHECK-NOT: define {{.*}} dllexport {{.*}} @_ZN1cIdE1fEv
 
 template <class T>
 struct outer {
-  void f();
+  void f() {}
+  void g();
+  inline static int u = 0;
+  static int v;
+  // MinGW-GCC and Clang does not apply 'dllexport' to inner type and its sub-elements in template class.
   struct inner {
-    void f();
+    void f() {}
+    void g();
+    inline static int u = 0;
+    static int v;
   };
 };
 
-template <class T> void outer<T>::f() {}
-template <class T> void outer<T>::inner::f() {}
+template <class T> void outer<T>::g() {}
+template <class T> void outer<T>::inner::g() {}
+template <class T> int outer<T>::v = 0;
+template <class T> int outer<T>::inner::v = 0;
 
-template class __declspec(dllexport) outer<int>;
+// #4
+template struct __declspec(dllexport) outer<int>;
 
-// CHECK: define {{.*}} dllexport {{.*}} @_ZN5outerIiE1fEv
-// CHECK-NOT: define {{.*}} dllexport {{.*}} @_ZN5outerIiE5inner1fEv
-
-extern template class __declspec(dllimport) outer<char>;
+// #5
+extern template struct __declspec(dllimport) outer<char>;
 USEMEMFUNC(outer<char>, f)
+USEMEMFUNC(outer<char>, g)
+USEMEMFUNC(outer<char>, u)
+USEMEMFUNC(outer<char>, v)
 USEMEMFUNC(outer<char>::inner, f)
+USEMEMFUNC(outer<char>::inner, g)
+USEMEMFUNC(outer<char>::inner, u)
+USEMEMFUNC(outer<char>::inner, v)
+
+
+// #1 variables
+// CHECK: @_ZN1cIiE1uE = {{.*}} dllexport {{.*}}
+// CHECK: @_ZN1cIiE1vE = {{.*}} dllexport {{.*}}
+
+// #2 variables
+// CHECK: @_ZN1cIcE1uE = {{.*}} dllexport {{.*}}
+// CHECK: @_ZN1cIcE1vE = {{.*}} dllexport {{.*}}
+
+// #3 variables
+// CHECK: @_ZN1cIdE1uE = {{.*}}
+// CHECK-NOT: @_ZN1cIcE1uE = {{.*}} dllexport {{.*}}
+// CHECK: @_ZN1cIdE1vE = {{.*}}
+// CHECK-NOT: @_ZN1cIcE1vE = {{.*}} dllexport {{.*}}
+
+// #4 variables
+// CHECK: @_ZN5outerIiE1uE = {{.*}} dllexport {{.*}}
+// CHECK: @_ZN5outerIiE1vE = {{.*}} dllexport {{.*}}
+// CHECK: @_ZN5outerIiE5inner1uE = {{.*}}
+// CHECK-NOT: @_ZN5outerIiE5inner1uE = {{.*}} dllexport {{.*}}
+// CHECK: @_ZN5outerIiE5inner1vE = {{.*}}
+// CHECK-NOT: @_ZN5outerIiE5inner1vE = {{.*}} dllexport {{.*}}
+
+// #5 variables
+// CHECK: @_ZN5outerIcE1uE = external dllimport {{.*}}
+// CHECK: @_ZN5outerIcE1vE = external dllimport {{.*}}
+// CHECK-NOT: @_ZN5outerIcE5inner1uE = dllimport {{.*}}
+// CHECK-NOT: @_ZN5outerIcE5inner1vE = dllimport {{.*}}
+// CHECK: @_ZN5outerIcE5inner1uE = external {{.*}}
+// CHECK: @_ZN5outerIcE5inner1vE = external {{.*}}
+
+
+// #1 functions
+// CHECK: define {{.*}} dllexport {{.*}} @_ZN1cIiE1fEv
+// CHECK: define {{.*}} dllexport {{.*}} @_ZN1cIiE1gEv
+
+// #2 functions
+// CHECK: define {{.*}} dllexport {{.*}} @_ZN1cIcE1fEv
+// CHECK: define {{.*}} dllexport {{.*}} @_ZN1cIcE1gEv
+
+// #3 functions
+// CHECK-NOT: define {{.*}} dllexport {{.*}} @_ZN1cIdE1fEv
+// CHECK-NOT: define {{.*}} dllexport {{.*}} @_ZN1cIdE1gEv
+
+// #4 functions
+// CHECK: define {{.*}} dllexport {{.*}} @_ZN5outerIiE1fEv
+// CHECK: define {{.*}} dllexport {{.*}} @_ZN5outerIiE1gEv
+// CHECK-NOT: define {{.*}} dllexport {{.*}} @_ZN5outerIiE5inner1fEv
+// CHECK-NOT: define {{.*}} dllexport {{.*}} @_ZN5outerIiE5inner1gEv
 
+// #5 functions
 // CHECK: declare dllimport {{.*}} @_ZN5outerIcE1fEv
-// CHECK: define {{.*}} @_ZN5outerIcE5inner1fEv
+// CHECK: declare dllimport {{.*}} @_ZN5outerIcE1gEv
+// CHECK-NOT: declare dllimport {{.*}} @_ZN5outerIcE5inner1fEv
+// CHECK-NOT: declare dllimport {{.*}} @_ZN5outerIcE5inner1gEv
+// CHECK-NOT: define {{.*}} @_ZN5outerIcE1fEv
+// CHECK-NOT: define {{.*}} @_ZN5outerIcE5inner1fEv
+// CHECK-NOT: define {{.*}} @_ZN5outerIcE1gEv
+// CHECK-NOT: define {{.*}} @_ZN5outerIcE5inner1gEv

libcxx/include/__config

@@ -530,6 +530,26 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_HIDE_FROM_ABI_AFTER_V1 _LIBCPP_HIDE_FROM_ABI
 #  endif
 
+//// ** in-progress: this description block should be here or merged block above? **
+// _LIBCPP_HIDE_FROM_ABI(_AFTER_V1) is mandatory for member functions in a inner class in a class template
+// (e.g. std::basic_ostream<...>::sentry::sentry(...) ) due to strange behavior of MinGW-GCC about
+// instantiation combined with dllimport/dllexport described below. Former clang didn't do this buggy behavior
+// but will be aligned to GCC for platform compatibility (in particluar, required by some of libstdc++ package).
+// Thus, such member functions exist from a past (they are, ostream::sentry::sentry, ostream::ostream::~sentry
+// and istream::sentry::sentry only) need to be HIDE_FROM_ABI but simply attaching simply ABI on other platforms.
+// So it's needed a dedicated keyword named _LIBCPP_HIDE_FROM_ABI_MINGW_OR_AFTER_V1 to affects only for MinGW
+// target (and, Cygwin too). For other platforms, that is expanded to _LIBCPP_HIDE_FROM_ABI_AFTER_V1 because at
+// a time to fix V2 ABI comes, _LIBCPP_HIDE_FROM_ABI_MINGW_OR_AFTER_V1 can be simply replaced into
+// _LIBCPP_HIDE_FROM_ABI_AFTER_V1 and be completely removed.
+// If time to a new class in a class template comes, all non-inline member functions of that new inner class must
+// be declared with _LIBCPP_HIDE_FROM_ABI_AFTER_V1 otherwise they build to DLL will be inaccessible by MinGW-GCC.
+//// ** in-progress: describe peculiar behavior of MinGW-GCC **
+#  if defined(__MINGW32__) || defined(__CYGWIN__)
+#    define _LIBCPP_HIDE_FROM_ABI_MINGW_OR_AFTER_V1 _LIBCPP_HIDE_FROM_ABI
+#  else
+#    define _LIBCPP_HIDE_FROM_ABI_MINGW_OR_AFTER_V1 _LIBCPP_HIDE_FROM_ABI_AFTER_V1
+#  endif
+
 // TODO: Remove this workaround once we drop support for Clang 16
 #  if __has_warning("-Wc++23-extensions")
 #    define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED_CXX23_EXTENSION _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++23-extensions")

libcxx/include/__ostream/basic_ostream.h

@@ -186,8 +186,8 @@ class basic_ostream<_CharT, _Traits>::sentry {
   basic_ostream<_CharT, _Traits>& __os_;
 
 public:
-  explicit sentry(basic_ostream<_CharT, _Traits>& __os);
-  ~sentry();
+  explicit inline _LIBCPP_HIDE_FROM_ABI_MINGW_OR_AFTER_V1 sentry(basic_ostream<_CharT, _Traits>& __os);
+  inline _LIBCPP_HIDE_FROM_ABI_MINGW_OR_AFTER_V1 ~sentry();
   sentry(const sentry&)            = delete;
   sentry& operator=(const sentry&) = delete;
 

libcxx/include/istream

@@ -309,7 +309,8 @@ class basic_istream<_CharT, _Traits>::sentry {
   bool __ok_;
 
 public:
-  explicit sentry(basic_istream<_CharT, _Traits>& __is, bool __noskipws = false);
+  explicit inline _LIBCPP_HIDE_FROM_ABI_MINGW_OR_AFTER_V1
+  sentry(basic_istream<_CharT, _Traits>& __is, bool __noskipws = false);
   //    ~sentry() = default;
 
   _LIBCPP_HIDE_FROM_ABI explicit operator bool() const { return __ok_; }

libcxx/test/libcxx/containers/sequences/deque/incomplete.pass.cpp

@@ -11,7 +11,7 @@
 // deque()
 // deque::iterator()
 
-// ADDITIONAL_COMPILE_FLAGS: -Wno-macro-redefined -D_LIBCPP_ABI_INCOMPLETE_TYPES_IN_DEQUE
+// ADDITIONAL_COMPILE_FLAGS: -Wno-error -Wno-macro-redefined -D_LIBCPP_ABI_INCOMPLETE_TYPES_IN_DEQUE
 
 #include <deque>
 #include <cassert>

libcxx/utils/ci/run-buildbot

@@ -353,6 +353,14 @@ generic-gcc-cxx11)
                    -DLIBUNWIND_ENABLE_WERROR=NO
     check-runtimes
 ;;
+generic-gcc-abi-unstable)
+    clean
+    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-abi-unstable.cmake" \
+                   -DLIBCXX_ENABLE_WERROR=NO \
+                   -DLIBCXXABI_ENABLE_WERROR=NO \
+                   -DLIBUNWIND_ENABLE_WERROR=NO
+    check-runtimes
+;;
 #
 # Sanitizers
 #