diff --git a/dlls/msvcirt/msvcirt.c b/dlls/msvcirt/msvcirt.c
index 0e018d5d9d8..5364c868f0d 100644
--- a/dlls/msvcirt/msvcirt.c
+++ b/dlls/msvcirt/msvcirt.c
@@ -180,6 +180,8 @@ extern const vtable_ptr MSVCP_ostream_vtable;
 extern const vtable_ptr MSVCP_ostream_withassign_vtable;
 /* ??_7istream@@6B@ */
 extern const vtable_ptr MSVCP_istream_vtable;
+/* ??_7istream_withassign@@6B@ */
+extern const vtable_ptr MSVCP_istream_withassign_vtable;
 
 #ifndef __GNUC__
 void __asm_dummy_vtables(void) {
@@ -240,6 +242,8 @@ void __asm_dummy_vtables(void) {
             VTABLE_ADD_FUNC(ostream_vector_dtor));
     __ASM_VTABLE(istream,
             VTABLE_ADD_FUNC(istream_vector_dtor));
+    __ASM_VTABLE(istream_withassign,
+            VTABLE_ADD_FUNC(istream_vector_dtor));
 #ifndef __GNUC__
 }
 #endif
@@ -251,6 +255,7 @@ void __asm_dummy_vtables(void) {
 /* ??_8ostream_withassign@@7B@ */
 const int ostream_vbtable[] = {0, VBTABLE_ENTRY(ostream, FIELD_OFFSET(ostream, vbtable), ios)};
 /* ??_8istream@@7B@ */
+/* ??_8istream_withassign@@7B@ */
 const int istream_vbtable[] = {0, VBTABLE_ENTRY(istream, FIELD_OFFSET(istream, vbtable), ios)};
 
 DEFINE_RTTI_DATA0(streambuf, 0, ".?AVstreambuf@@")
@@ -262,6 +267,8 @@ DEFINE_RTTI_DATA1(ostream, sizeof(ostream), &ios_rtti_base_descriptor, ".?AVostr
 DEFINE_RTTI_DATA2(ostream_withassign, sizeof(ostream),
     &ostream_rtti_base_descriptor, &ios_rtti_base_descriptor, ".?AVostream_withassign@@")
 DEFINE_RTTI_DATA1(istream, sizeof(istream), &ios_rtti_base_descriptor, ".?AVistream@@")
+DEFINE_RTTI_DATA2(istream_withassign, sizeof(istream),
+    &istream_rtti_base_descriptor, &ios_rtti_base_descriptor, ".?AVistream_withassign@@")
 
 /* ??0streambuf@@IAE@PADH@Z */
 /* ??0streambuf@@IEAA@PEADH@Z */
@@ -2987,6 +2994,8 @@ istream* __thiscall istream_ctor(istream *this, BOOL virt_init)
 
 /* ??1istream@@UAE@XZ */
 /* ??1istream@@UEAA@XZ */
+/* ??1istream_withassign@@UAE@XZ */
+/* ??1istream_withassign@@UEAA@XZ */
 DEFINE_THISCALL_WRAPPER(istream_dtor, 4)
 void __thiscall istream_dtor(ios *base)
 {
@@ -2997,6 +3006,8 @@ void __thiscall istream_dtor(ios *base)
 
 /* ??4istream@@IAEAAV0@PAVstreambuf@@@Z */
 /* ??4istream@@IEAAAEAV0@PEAVstreambuf@@@Z */
+/* ??4istream_withassign@@QAEAAVistream@@PAVstreambuf@@@Z */
+/* ??4istream_withassign@@QEAAAEAVistream@@PEAVstreambuf@@@Z */
 DEFINE_THISCALL_WRAPPER(istream_assign_sb, 8)
 istream* __thiscall istream_assign_sb(istream *this, streambuf *sb)
 {
@@ -3018,6 +3029,10 @@ istream* __thiscall istream_assign_sb(istream *this, streambuf *sb)
 
 /* ??4istream@@IAEAAV0@ABV0@@Z */
 /* ??4istream@@IEAAAEAV0@AEBV0@@Z */
+/* ??4istream_withassign@@QAEAAV0@ABV0@@Z */
+/* ??4istream_withassign@@QEAAAEAV0@AEBV0@@Z */
+/* ??4istream_withassign@@QAEAAVistream@@ABV1@@Z */
+/* ??4istream_withassign@@QEAAAEAVistream@@AEBV1@@Z */
 DEFINE_THISCALL_WRAPPER(istream_assign, 8)
 istream* __thiscall istream_assign(istream *this, const istream *rhs)
 {
@@ -3026,6 +3041,8 @@ istream* __thiscall istream_assign(istream *this, const istream *rhs)
 
 /* ??_Distream@@QAEXXZ */
 /* ??_Distream@@QEAAXXZ */
+/* ??_Distream_withassign@@QAEXXZ */
+/* ??_Distream_withassign@@QEAAXXZ */
 DEFINE_THISCALL_WRAPPER(istream_vbase_dtor, 4)
 void __thiscall istream_vbase_dtor(istream *this)
 {
@@ -3038,6 +3055,7 @@ void __thiscall istream_vbase_dtor(istream *this)
 }
 
 /* ??_Eistream@@UAEPAXI@Z */
+/* ??_Eistream_withassign@@UAEPAXI@Z */
 DEFINE_THISCALL_WRAPPER(istream_vector_dtor, 8)
 istream* __thiscall istream_vector_dtor(ios *base, unsigned int flags)
 {
@@ -3061,6 +3079,7 @@ istream* __thiscall istream_vector_dtor(ios *base, unsigned int flags)
 }
 
 /* ??_Gistream@@UAEPAXI@Z */
+/* ??_Gistream_withassign@@UAEPAXI@Z */
 DEFINE_THISCALL_WRAPPER(istream_scalar_dtor, 8)
 istream* __thiscall istream_scalar_dtor(ios *base, unsigned int flags)
 {
@@ -3837,6 +3856,33 @@ istream* __cdecl istream_ws(istream *this)
     return this;
 }
 
+/* ??0istream_withassign@@QAE@ABV0@@Z */
+/* ??0istream_withassign@@QEAA@AEBV0@@Z */
+DEFINE_THISCALL_WRAPPER(istream_withassign_copy_ctor, 12)
+istream* __thiscall istream_withassign_copy_ctor(istream *this, const istream *copy, BOOL virt_init)
+{
+    FIXME("(%p %p %d) stub\n", this, copy, virt_init);
+    return this;
+}
+
+/* ??0istream_withassign@@QAE@PAVstreambuf@@@Z */
+/* ??0istream_withassign@@QEAA@PEAVstreambuf@@@Z */
+DEFINE_THISCALL_WRAPPER(istream_withassign_sb_ctor, 12)
+istream* __thiscall istream_withassign_sb_ctor(istream *this, streambuf *sb, BOOL virt_init)
+{
+    FIXME("(%p %p %d) stub\n", this, sb, virt_init);
+    return this;
+}
+
+/* ??0istream_withassign@@QAE@XZ */
+/* ??0istream_withassign@@QEAA@XZ */
+DEFINE_THISCALL_WRAPPER(istream_withassign_ctor, 8)
+istream* __thiscall istream_withassign_ctor(istream *this, BOOL virt_init)
+{
+    FIXME("(%p %d) stub\n", this, virt_init);
+    return this;
+}
+
 /******************************************************************
  *		 ??0ostrstream@@QAE@XZ (MSVCRTI.@)
  */
@@ -3914,6 +3960,7 @@ static void init_io(void *base)
     init_ostream_rtti(base);
     init_ostream_withassign_rtti(base);
     init_istream_rtti(base);
+    init_istream_withassign_rtti(base);
 #endif
 }
 
diff --git a/dlls/msvcirt/msvcirt.spec b/dlls/msvcirt/msvcirt.spec
index 67c30285960..4438b31673f 100644
--- a/dlls/msvcirt/msvcirt.spec
+++ b/dlls/msvcirt/msvcirt.spec
@@ -54,12 +54,12 @@
 @ cdecl -arch=win64 ??0istream@@IEAA@XZ(ptr long) istream_ctor
 @ thiscall -arch=win32 ??0istream@@QAE@PAVstreambuf@@@Z(ptr ptr long) istream_sb_ctor
 @ cdecl -arch=win64 ??0istream@@QEAA@PEAVstreambuf@@@Z(ptr ptr long) istream_sb_ctor
-@ stub -arch=win32 ??0istream_withassign@@QAE@ABV0@@Z  # __thiscall istream_withassign::istream_withassign(class istream_withassign const &)
-@ stub -arch=win64 ??0istream_withassign@@QEAA@AEBV0@@Z
-@ stub -arch=win32 ??0istream_withassign@@QAE@PAVstreambuf@@@Z  # __thiscall istream_withassign::istream_withassign(class streambuf *)
-@ stub -arch=win64 ??0istream_withassign@@QEAA@PEAVstreambuf@@@Z
-@ stub -arch=win32 ??0istream_withassign@@QAE@XZ  # __thiscall istream_withassign::istream_withassign(void)
-@ stub -arch=win64 ??0istream_withassign@@QEAA@XZ
+@ thiscall -arch=win32 ??0istream_withassign@@QAE@ABV0@@Z(ptr ptr long) istream_withassign_copy_ctor
+@ cdecl -arch=win64 ??0istream_withassign@@QEAA@AEBV0@@Z(ptr ptr long) istream_withassign_copy_ctor
+@ thiscall -arch=win32 ??0istream_withassign@@QAE@PAVstreambuf@@@Z(ptr ptr long) istream_withassign_sb_ctor
+@ cdecl -arch=win64 ??0istream_withassign@@QEAA@PEAVstreambuf@@@Z(ptr ptr long) istream_withassign_sb_ctor
+@ thiscall -arch=win32 ??0istream_withassign@@QAE@XZ(ptr long) istream_withassign_ctor
+@ cdecl -arch=win64 ??0istream_withassign@@QEAA@XZ(ptr long) istream_withassign_ctor
 @ stub -arch=win32 ??0istrstream@@QAE@ABV0@@Z  # __thiscall istrstream::istrstream(class istrstream const &)
 @ stub -arch=win64 ??0istrstream@@QEAA@AEBV0@@Z
 @ stub -arch=win32 ??0istrstream@@QAE@PAD@Z  # __thiscall istrstream::istrstream(char *)
@@ -146,8 +146,8 @@
 @ stub -arch=win64 ??1iostream@@UEAA@XZ
 @ thiscall -arch=win32 ??1istream@@UAE@XZ(ptr) istream_dtor
 @ cdecl -arch=win64 ??1istream@@UEAA@XZ(ptr) istream_dtor
-@ stub -arch=win32 ??1istream_withassign@@UAE@XZ  # virtual __thiscall istream_withassign::~istream_withassign(void)
-@ stub -arch=win64 ??1istream_withassign@@UEAA@XZ
+@ thiscall -arch=win32 ??1istream_withassign@@UAE@XZ(ptr) istream_dtor
+@ cdecl -arch=win64 ??1istream_withassign@@UEAA@XZ(ptr) istream_dtor
 @ stub -arch=win32 ??1istrstream@@UAE@XZ  # virtual __thiscall istrstream::~istrstream(void)
 @ stub -arch=win64 ??1istrstream@@UEAA@XZ
 @ thiscall -arch=win32 ??1logic_error@@UAE@XZ(ptr) MSVCP_logic_error_dtor
@@ -190,12 +190,12 @@
 @ cdecl -arch=win64 ??4istream@@IEAAAEAV0@AEBV0@@Z(ptr ptr) istream_assign
 @ thiscall -arch=win32 ??4istream@@IAEAAV0@PAVstreambuf@@@Z(ptr ptr) istream_assign_sb
 @ cdecl -arch=win64 ??4istream@@IEAAAEAV0@PEAVstreambuf@@@Z(ptr ptr) istream_assign_sb
-@ stub -arch=win32 ??4istream_withassign@@QAEAAV0@ABV0@@Z  # class istream_withassign & __thiscall istream_withassign::operator=(class istream_withassign const &)
-@ stub -arch=win64 ??4istream_withassign@@QEAAAEAV0@AEBV0@@Z
-@ stub -arch=win32 ??4istream_withassign@@QAEAAVistream@@ABV1@@Z  # class istream & __thiscall istream_withassign::operator=(class istream const &)
-@ stub -arch=win64 ??4istream_withassign@@QEAAAEAVistream@@AEBV1@@Z
-@ stub -arch=win32 ??4istream_withassign@@QAEAAVistream@@PAVstreambuf@@@Z  # class istream & __thiscall istream_withassign::operator=(class streambuf *)
-@ stub -arch=win64 ??4istream_withassign@@QEAAAEAVistream@@PEAVstreambuf@@@Z
+@ thiscall -arch=win32 ??4istream_withassign@@QAEAAV0@ABV0@@Z(ptr ptr) istream_assign
+@ cdecl -arch=win64 ??4istream_withassign@@QEAAAEAV0@AEBV0@@Z(ptr ptr) istream_assign
+@ thiscall -arch=win32 ??4istream_withassign@@QAEAAVistream@@ABV1@@Z(ptr ptr) istream_assign
+@ cdecl -arch=win64 ??4istream_withassign@@QEAAAEAVistream@@AEBV1@@Z(ptr ptr) istream_assign
+@ thiscall -arch=win32 ??4istream_withassign@@QAEAAVistream@@PAVstreambuf@@@Z(ptr ptr) istream_assign_sb
+@ cdecl -arch=win64 ??4istream_withassign@@QEAAAEAVistream@@PEAVstreambuf@@@Z(ptr ptr) istream_assign_sb
 @ stub -arch=win32 ??4istrstream@@QAEAAV0@ABV0@@Z  # class istrstream & __thiscall istrstream::operator=(class istrstream const &)
 @ stub -arch=win64 ??4istrstream@@QEAAAEAV0@AEBV0@@Z
 @ thiscall -arch=win32 ??4logic_error@@QAEAAV0@ABV0@@Z(ptr ptr) MSVCP_logic_error_assign
@@ -309,7 +309,7 @@
 @ extern ??_7ios@@6B@ MSVCP_ios_vtable
 # @ extern ??_7iostream@@6B@  # const iostream::`vftable'
 @ extern ??_7istream@@6B@ MSVCP_istream_vtable
-# @ extern ??_7istream_withassign@@6B@  # const istream_withassign::`vftable'
+@ extern ??_7istream_withassign@@6B@ MSVCP_istream_vtable
 # @ extern ??_7istrstream@@6B@  # const istrstream::`vftable'
 @ extern ??_7logic_error@@6B@ MSVCP_logic_error_vtable
 # @ extern ??_7ofstream@@6B@  # const ofstream::`vftable'
@@ -327,7 +327,7 @@
 # @ extern ??_8iostream@@7Bistream@@@  # const iostream::`vbtable'{for `istream'}
 # @ extern ??_8iostream@@7Bostream@@@  # const iostream::`vbtable'{for `ostream'}
 @ extern ??_8istream@@7B@ istream_vbtable
-# @ extern ??_8istream_withassign@@7B@  # const istream_withassign::`vbtable'
+@ extern ??_8istream_withassign@@7B@ istream_vbtable
 # @ extern ??_8istrstream@@7B@  # const istrstream::`vbtable'
 # @ extern ??_8ofstream@@7B@  # const ofstream::`vbtable'
 @ extern ??_8ostream@@7B@ ostream_vbtable
@@ -345,8 +345,8 @@
 @ stub -arch=win64 ??_Diostream@@QEAAXXZ
 @ thiscall -arch=win32 ??_Distream@@QAEXXZ(ptr) istream_vbase_dtor
 @ cdecl -arch=win64 ??_Distream@@QEAAXXZ(ptr) istream_vbase_dtor
-@ stub -arch=win32 ??_Distream_withassign@@QAEXXZ  # void __thiscall istream_withassign::`vbase destructor'(void)
-@ stub -arch=win64 ??_Distream_withassign@@QEAAXXZ
+@ thiscall -arch=win32 ??_Distream_withassign@@QAEXXZ(ptr) istream_vbase_dtor
+@ cdecl -arch=win64 ??_Distream_withassign@@QEAAXXZ(ptr) istream_vbase_dtor
 @ stub -arch=win32 ??_Distrstream@@QAEXXZ  # void __thiscall istrstream::`vbase destructor'(void)
 @ stub -arch=win64 ??_Distrstream@@QEAAXXZ
 @ stub -arch=win32 ??_Dofstream@@QAEXXZ  # void __thiscall ofstream::`vbase destructor'(void)
@@ -368,7 +368,7 @@
 @ thiscall -arch=win32 ??_Eios@@UAEPAXI@Z(ptr long) ios_vector_dtor
 @ stub -arch=win32 ??_Eiostream@@UAEPAXI@Z  # virtual void * __thiscall iostream::`vector deleting destructor'(unsigned int)
 @ thiscall -arch=win32 ??_Eistream@@UAEPAXI@Z(ptr long) istream_vector_dtor
-@ stub -arch=win32 ??_Eistream_withassign@@UAEPAXI@Z  # virtual void * __thiscall istream_withassign::`vector deleting destructor'(unsigned int)
+@ thiscall -arch=win32 ??_Eistream_withassign@@UAEPAXI@Z(ptr long) istream_vector_dtor
 @ stub -arch=win32 ??_Eistrstream@@UAEPAXI@Z  # virtual void * __thiscall istrstream::`vector deleting destructor'(unsigned int)
 @ thiscall -arch=win32 ??_Elogic_error@@UAEPAXI@Z(ptr long) MSVCP_logic_error_vector_dtor
 @ stub -arch=win32 ??_Eofstream@@UAEPAXI@Z  # virtual void * __thiscall ofstream::`vector deleting destructor'(unsigned int)
@@ -387,7 +387,7 @@
 @ thiscall -arch=win32 ??_Gios@@UAEPAXI@Z(ptr long) ios_scalar_dtor
 @ stub -arch=win32 ??_Giostream@@UAEPAXI@Z  # virtual void * __thiscall iostream::`scalar deleting destructor'(unsigned int)
 @ thiscall -arch=win32 ??_Gistream@@UAEPAXI@Z(ptr long) istream_scalar_dtor
-@ stub -arch=win32 ??_Gistream_withassign@@UAEPAXI@Z  # virtual void * __thiscall istream_withassign::`scalar deleting destructor'(unsigned int)
+@ thiscall -arch=win32 ??_Gistream_withassign@@UAEPAXI@Z(ptr long) istream_scalar_dtor
 @ stub -arch=win32 ??_Gistrstream@@UAEPAXI@Z  # virtual void * __thiscall istrstream::`scalar deleting destructor'(unsigned int)
 @ thiscall -arch=win32 ??_Glogic_error@@UAEPAXI@Z(ptr long) MSVCP_logic_error_scalar_dtor
 @ stub -arch=win32 ??_Gofstream@@UAEPAXI@Z  # virtual void * __thiscall ofstream::`scalar deleting destructor'(unsigned int)
diff --git a/dlls/msvcrt20/msvcrt20.spec b/dlls/msvcrt20/msvcrt20.spec
index ff4ed730edb..a5070f4d688 100644
--- a/dlls/msvcrt20/msvcrt20.spec
+++ b/dlls/msvcrt20/msvcrt20.spec
@@ -48,12 +48,12 @@
 @ cdecl -arch=win64 ??0istream@@IEAA@XZ(ptr long) msvcirt.??0istream@@IEAA@XZ
 @ thiscall -arch=win32 ??0istream@@QAE@PAVstreambuf@@@Z(ptr ptr long) msvcirt.??0istream@@QAE@PAVstreambuf@@@Z
 @ cdecl -arch=win64 ??0istream@@QEAA@PEAVstreambuf@@@Z(ptr ptr long) msvcirt.??0istream@@QEAA@PEAVstreambuf@@@Z
-@ stub -arch=win32 ??0istream_withassign@@QAE@ABV0@@Z
-@ stub -arch=win64 ??0istream_withassign@@QEAA@AEBV0@@Z
-@ stub -arch=win32 ??0istream_withassign@@QAE@PAVstreambuf@@@Z
-@ stub -arch=win64 ??0istream_withassign@@QEAA@PEAVstreambuf@@@Z
-@ stub -arch=win32 ??0istream_withassign@@QAE@XZ
-@ stub -arch=win64 ??0istream_withassign@@QEAA@XZ
+@ thiscall -arch=win32 ??0istream_withassign@@QAE@ABV0@@Z(ptr ptr long) msvcirt.??0istream_withassign@@QAE@ABV0@@Z
+@ cdecl -arch=win64 ??0istream_withassign@@QEAA@AEBV0@@Z(ptr ptr long) msvcirt.??0istream_withassign@@QEAA@AEBV0@@Z
+@ thiscall -arch=win32 ??0istream_withassign@@QAE@PAVstreambuf@@@Z(ptr ptr long) msvcirt.??0istream_withassign@@QAE@PAVstreambuf@@@Z
+@ cdecl -arch=win64 ??0istream_withassign@@QEAA@PEAVstreambuf@@@Z(ptr ptr long) msvcirt.??0istream_withassign@@QEAA@PEAVstreambuf@@@Z
+@ thiscall -arch=win32 ??0istream_withassign@@QAE@XZ(ptr long) msvcirt.??0istream_withassign@@QAE@XZ
+@ cdecl -arch=win64 ??0istream_withassign@@QEAA@XZ(ptr long) msvcirt.??0istream_withassign@@QEAA@XZ
 @ stub -arch=win32 ??0istrstream@@QAE@ABV0@@Z
 @ stub -arch=win64 ??0istrstream@@QEAA@AEBV0@@Z
 @ stub -arch=win32 ??0istrstream@@QAE@PAD@Z
@@ -132,8 +132,8 @@
 @ stub -arch=win64 ??1iostream@@UEAA@XZ
 @ thiscall -arch=win32 ??1istream@@UAE@XZ(ptr) msvcirt.??1istream@@UAE@XZ
 @ cdecl -arch=win64 ??1istream@@UEAA@XZ(ptr) msvcirt.??1istream@@UEAA@XZ
-@ stub -arch=win32 ??1istream_withassign@@UAE@XZ
-@ stub -arch=win64 ??1istream_withassign@@UEAA@XZ
+@ thiscall -arch=win32 ??1istream_withassign@@UAE@XZ(ptr) msvcirt.??1istream_withassign@@UAE@XZ
+@ cdecl -arch=win64 ??1istream_withassign@@UEAA@XZ(ptr) msvcirt.??1istream_withassign@@UEAA@XZ
 @ stub -arch=win32 ??1istrstream@@UAE@XZ
 @ stub -arch=win64 ??1istrstream@@UEAA@XZ
 @ stub -arch=win32 ??1ofstream@@UAE@XZ
@@ -176,12 +176,12 @@
 @ cdecl -arch=win64 ??4istream@@IEAAAEAV0@AEBV0@@Z(ptr ptr) msvcirt.??4istream@@IEAAAEAV0@AEBV0@@Z
 @ thiscall -arch=win32 ??4istream@@IAEAAV0@PAVstreambuf@@@Z(ptr ptr) msvcirt.??4istream@@IAEAAV0@PAVstreambuf@@@Z
 @ cdecl -arch=win64 ??4istream@@IEAAAEAV0@PEAVstreambuf@@@Z(ptr ptr) msvcirt.??4istream@@IEAAAEAV0@PEAVstreambuf@@@Z
-@ stub -arch=win32 ??4istream_withassign@@QAEAAV0@ABV0@@Z
-@ stub -arch=win64 ??4istream_withassign@@QEAAAEAV0@AEBV0@@Z
-@ stub -arch=win32 ??4istream_withassign@@QAEAAVistream@@ABV1@@Z
-@ stub -arch=win64 ??4istream_withassign@@QEAAAEAVistream@@AEBV1@@Z
-@ stub -arch=win32 ??4istream_withassign@@QAEAAVistream@@PAVstreambuf@@@Z
-@ stub -arch=win64 ??4istream_withassign@@QEAAAEAVistream@@PEAVstreambuf@@@Z
+@ thiscall -arch=win32 ??4istream_withassign@@QAEAAV0@ABV0@@Z(ptr ptr) msvcirt.??4istream_withassign@@QAEAAV0@ABV0@@Z
+@ cdecl -arch=win64 ??4istream_withassign@@QEAAAEAV0@AEBV0@@Z(ptr ptr) msvcirt.??4istream_withassign@@QEAAAEAV0@AEBV0@@Z
+@ thiscall -arch=win32 ??4istream_withassign@@QAEAAVistream@@ABV1@@Z(ptr ptr) msvcirt.??4istream_withassign@@QAEAAVistream@@ABV1@@Z
+@ cdecl -arch=win64 ??4istream_withassign@@QEAAAEAVistream@@AEBV1@@Z(ptr ptr) msvcirt.??4istream_withassign@@QEAAAEAVistream@@AEBV1@@Z
+@ thiscall -arch=win32 ??4istream_withassign@@QAEAAVistream@@PAVstreambuf@@@Z(ptr ptr) msvcirt.??4istream_withassign@@QAEAAVistream@@PAVstreambuf@@@Z
+@ cdecl -arch=win64 ??4istream_withassign@@QEAAAEAVistream@@PEAVstreambuf@@@Z(ptr ptr) msvcirt.??4istream_withassign@@QEAAAEAVistream@@PEAVstreambuf@@@Z
 @ stub -arch=win32 ??4istrstream@@QAEAAV0@ABV0@@Z
 @ stub -arch=win64 ??4istrstream@@QEAAAEAV0@AEBV0@@Z
 @ stub -arch=win32 ??4ofstream@@QAEAAV0@ABV0@@Z
@@ -292,7 +292,7 @@
 @ extern ??_7ios@@6B@ msvcirt.??_7ios@@6B@
 # @ extern ??_7iostream@@6B@
 @ extern ??_7istream@@6B@ msvcirt.??_7istream@@6B@
-# @ extern ??_7istream_withassign@@6B@
+@ extern ??_7istream_withassign@@6B@ msvcirt.??_7istream_withassign@@6B@
 # @ extern ??_7istrstream@@6B@
 # @ extern ??_7ofstream@@6B@
 @ extern ??_7ostream@@6B@ msvcirt.??_7ostream@@6B@
@@ -309,7 +309,7 @@
 # @ extern ??_8iostream@@7Bistream@@@
 # @ extern ??_8iostream@@7Bostream@@@
 @ extern ??_8istream@@7B@ msvcirt.??_8istream@@7B@
-# @ extern ??_8istream_withassign@@7B@
+@ extern ??_8istream_withassign@@7B@ msvcirt.??_8istream_withassign@@7B@
 # @ extern ??_8istrstream@@7B@
 # @ extern ??_8ofstream@@7B@
 @ extern ??_8ostream@@7B@ msvcirt.??_8ostream@@7B@
@@ -327,8 +327,8 @@
 @ stub -arch=win64 ??_Diostream@@QEAAXXZ
 @ thiscall -arch=win32 ??_Distream@@QAEXXZ(ptr) msvcirt.??_Distream@@QAEXXZ
 @ cdecl -arch=win64 ??_Distream@@QEAAXXZ(ptr) msvcirt.??_Distream@@QEAAXXZ
-@ stub -arch=win32 ??_Distream_withassign@@QAEXXZ
-@ stub -arch=win64 ??_Distream_withassign@@QEAAXXZ
+@ thiscall -arch=win32 ??_Distream_withassign@@QAEXXZ(ptr) msvcirt.??_Distream_withassign@@QAEXXZ
+@ cdecl -arch=win64 ??_Distream_withassign@@QEAAXXZ(ptr) msvcirt.??_Distream_withassign@@QEAAXXZ
 @ stub -arch=win32 ??_Distrstream@@QAEXXZ
 @ stub -arch=win64 ??_Distrstream@@QEAAXXZ
 @ stub -arch=win32 ??_Dofstream@@QAEXXZ
@@ -350,7 +350,7 @@
 @ thiscall -arch=win32 ??_Eios@@UAEPAXI@Z(ptr long) msvcirt.??_Eios@@UAEPAXI@Z
 @ stub -arch=win32 ??_Eiostream@@UAEPAXI@Z
 @ thiscall -arch=win32 ??_Eistream@@UAEPAXI@Z(ptr long) msvcirt.??_Eistream@@UAEPAXI@Z
-@ stub -arch=win32 ??_Eistream_withassign@@UAEPAXI@Z
+@ thiscall -arch=win32 ??_Eistream_withassign@@UAEPAXI@Z(ptr long) msvcirt.??_Eistream_withassign@@UAEPAXI@Z
 @ stub -arch=win32 ??_Eistrstream@@UAEPAXI@Z
 @ stub -arch=win32 ??_Eofstream@@UAEPAXI@Z
 @ thiscall -arch=win32 ??_Eostream@@UAEPAXI@Z(ptr long) msvcirt.??_Eostream@@UAEPAXI@Z
@@ -368,7 +368,7 @@
 @ thiscall -arch=win32 ??_Gios@@UAEPAXI@Z(ptr long) msvcirt.??_Gios@@UAEPAXI@Z
 @ stub -arch=win32 ??_Giostream@@UAEPAXI@Z
 @ thiscall -arch=win32 ??_Gistream@@UAEPAXI@Z(ptr long) msvcirt.??_Gistream@@UAEPAXI@Z
-@ stub -arch=win32 ??_Gistream_withassign@@UAEPAXI@Z
+@ thiscall -arch=win32 ??_Gistream_withassign@@UAEPAXI@Z(ptr long) msvcirt.??_Gistream_withassign@@UAEPAXI@Z
 @ stub -arch=win32 ??_Gistrstream@@UAEPAXI@Z
 @ stub -arch=win32 ??_Gofstream@@UAEPAXI@Z
 @ thiscall -arch=win32 ??_Gostream@@UAEPAXI@Z(ptr long) msvcirt.??_Gostream@@UAEPAXI@Z
diff --git a/dlls/msvcrt40/msvcrt40.spec b/dlls/msvcrt40/msvcrt40.spec
index fc9a5dcbc85..935e48c2775 100644
--- a/dlls/msvcrt40/msvcrt40.spec
+++ b/dlls/msvcrt40/msvcrt40.spec
@@ -66,12 +66,12 @@
 @ cdecl -arch=win64 ??0istream@@IEAA@XZ(ptr long) msvcirt.??0istream@@IEAA@XZ
 @ thiscall -arch=win32 ??0istream@@QAE@PAVstreambuf@@@Z(ptr ptr long) msvcirt.??0istream@@QAE@PAVstreambuf@@@Z
 @ cdecl -arch=win64 ??0istream@@QEAA@PEAVstreambuf@@@Z(ptr ptr long) msvcirt.??0istream@@QEAA@PEAVstreambuf@@@Z
-@ stub -arch=win32 ??0istream_withassign@@QAE@ABV0@@Z
-@ stub -arch=win64 ??0istream_withassign@@QEAA@AEBV0@@Z
-@ stub -arch=win32 ??0istream_withassign@@QAE@PAVstreambuf@@@Z
-@ stub -arch=win64 ??0istream_withassign@@QEAA@PEAVstreambuf@@@Z
-@ stub -arch=win32 ??0istream_withassign@@QAE@XZ
-@ stub -arch=win64 ??0istream_withassign@@QEAA@XZ
+@ thiscall -arch=win32 ??0istream_withassign@@QAE@ABV0@@Z(ptr ptr long) msvcirt.??0istream_withassign@@QAE@ABV0@@Z
+@ cdecl -arch=win64 ??0istream_withassign@@QEAA@AEBV0@@Z(ptr ptr long) msvcirt.??0istream_withassign@@QEAA@AEBV0@@Z
+@ thiscall -arch=win32 ??0istream_withassign@@QAE@PAVstreambuf@@@Z(ptr ptr long) msvcirt.??0istream_withassign@@QAE@PAVstreambuf@@@Z
+@ cdecl -arch=win64 ??0istream_withassign@@QEAA@PEAVstreambuf@@@Z(ptr ptr long) msvcirt.??0istream_withassign@@QEAA@PEAVstreambuf@@@Z
+@ thiscall -arch=win32 ??0istream_withassign@@QAE@XZ(ptr long) msvcirt.??0istream_withassign@@QAE@XZ
+@ cdecl -arch=win64 ??0istream_withassign@@QEAA@XZ(ptr long) msvcirt.??0istream_withassign@@QEAA@XZ
 @ stub -arch=win32 ??0istrstream@@QAE@ABV0@@Z
 @ stub -arch=win64 ??0istrstream@@QEAA@AEBV0@@Z
 @ stub -arch=win32 ??0istrstream@@QAE@PAD@Z
@@ -162,8 +162,8 @@
 @ stub -arch=win64 ??1iostream@@UEAA@XZ
 @ thiscall -arch=win32 ??1istream@@UAE@XZ(ptr) msvcirt.??1istream@@UAE@XZ
 @ cdecl -arch=win64 ??1istream@@UEAA@XZ(ptr) msvcirt.??1istream@@UEAA@XZ
-@ stub -arch=win32 ??1istream_withassign@@UAE@XZ
-@ stub -arch=win64 ??1istream_withassign@@UEAA@XZ
+@ thiscall -arch=win32 ??1istream_withassign@@UAE@XZ(ptr) msvcirt.??1istream_withassign@@UAE@XZ
+@ cdecl -arch=win64 ??1istream_withassign@@UEAA@XZ(ptr) msvcirt.??1istream_withassign@@UEAA@XZ
 @ stub -arch=win32 ??1istrstream@@UAE@XZ
 @ stub -arch=win64 ??1istrstream@@UEAA@XZ
 @ thiscall -arch=win32 ??1logic_error@@UAE@XZ(ptr) msvcirt.??1logic_error@@UAE@XZ
@@ -218,12 +218,12 @@
 @ cdecl -arch=win64 ??4istream@@IEAAAEAV0@AEBV0@@Z(ptr ptr) msvcirt.??4istream@@IEAAAEAV0@AEBV0@@Z
 @ thiscall -arch=win32 ??4istream@@IAEAAV0@PAVstreambuf@@@Z(ptr ptr) msvcirt.??4istream@@IAEAAV0@PAVstreambuf@@@Z
 @ cdecl -arch=win64 ??4istream@@IEAAAEAV0@PEAVstreambuf@@@Z(ptr ptr) msvcirt.??4istream@@IEAAAEAV0@PEAVstreambuf@@@Z
-@ stub -arch=win32 ??4istream_withassign@@QAEAAV0@ABV0@@Z
-@ stub -arch=win64 ??4istream_withassign@@QEAAAEAV0@AEBV0@@Z
-@ stub -arch=win32 ??4istream_withassign@@QAEAAVistream@@ABV1@@Z
-@ stub -arch=win64 ??4istream_withassign@@QEAAAEAVistream@@AEBV1@@Z
-@ stub -arch=win32 ??4istream_withassign@@QAEAAVistream@@PAVstreambuf@@@Z
-@ stub -arch=win64 ??4istream_withassign@@QEAAAEAVistream@@PEAVstreambuf@@@Z
+@ thiscall -arch=win32 ??4istream_withassign@@QAEAAV0@ABV0@@Z(ptr ptr) msvcirt.??4istream_withassign@@QAEAAV0@ABV0@@Z
+@ cdecl -arch=win64 ??4istream_withassign@@QEAAAEAV0@AEBV0@@Z(ptr ptr) msvcirt.??4istream_withassign@@QEAAAEAV0@AEBV0@@Z
+@ thiscall -arch=win32 ??4istream_withassign@@QAEAAVistream@@ABV1@@Z(ptr ptr) msvcirt.??4istream_withassign@@QAEAAVistream@@ABV1@@Z
+@ cdecl -arch=win64 ??4istream_withassign@@QEAAAEAVistream@@AEBV1@@Z(ptr ptr) msvcirt.??4istream_withassign@@QEAAAEAVistream@@AEBV1@@Z
+@ thiscall -arch=win32 ??4istream_withassign@@QAEAAVistream@@PAVstreambuf@@@Z(ptr ptr) msvcirt.??4istream_withassign@@QAEAAVistream@@PAVstreambuf@@@Z
+@ cdecl -arch=win64 ??4istream_withassign@@QEAAAEAVistream@@PEAVstreambuf@@@Z(ptr ptr) msvcirt.??4istream_withassign@@QEAAAEAVistream@@PEAVstreambuf@@@Z
 @ stub -arch=win32 ??4istrstream@@QAEAAV0@ABV0@@Z
 @ stub -arch=win64 ??4istrstream@@QEAAAEAV0@AEBV0@@Z
 @ thiscall -arch=win32 ??4logic_error@@QAEAAV0@ABV0@@Z(ptr ptr) msvcirt.??4logic_error@@QAEAAV0@ABV0@@Z
@@ -344,7 +344,7 @@
 @ extern ??_7ios@@6B@ msvcirt.??_7ios@@6B@
 # @ extern ??_7iostream@@6B@
 @ extern ??_7istream@@6B@ msvcirt.??_7istream@@6B@
-# @ extern ??_7istream_withassign@@6B@
+@ extern ??_7istream_withassign@@6B@ msvcirt.??_7istream_withassign@@6B@
 # @ extern ??_7istrstream@@6B@
 @ extern ??_7logic_error@@6B@ msvcirt.??_7logic_error@@6B@
 # @ extern ??_7ofstream@@6B@
@@ -362,7 +362,7 @@
 # @ extern ??_8iostream@@7Bistream@@@
 # @ extern ??_8iostream@@7Bostream@@@
 @ extern ??_8istream@@7B@ msvcirt.??_8istream@@7B@
-# @ extern ??_8istream_withassign@@7B@
+@ extern ??_8istream_withassign@@7B@ msvcirt.??_8istream_withassign@@7B@
 # @ extern ??_8istrstream@@7B@
 # @ extern ??_8ofstream@@7B@
 @ extern ??_8ostream@@7B@ msvcirt.??_8ostream@@7B@
@@ -380,8 +380,8 @@
 @ stub -arch=win64 ??_Diostream@@QEAAXXZ
 @ thiscall -arch=win32 ??_Distream@@QAEXXZ(ptr) msvcirt.??_Distream@@QAEXXZ
 @ cdecl -arch=win64 ??_Distream@@QEAAXXZ(ptr) msvcirt.??_Distream@@QEAAXXZ
-@ stub -arch=win32 ??_Distream_withassign@@QAEXXZ
-@ stub -arch=win64 ??_Distream_withassign@@QEAAXXZ
+@ thiscall -arch=win32 ??_Distream_withassign@@QAEXXZ(ptr) msvcirt.??_Distream_withassign@@QAEXXZ
+@ cdecl -arch=win64 ??_Distream_withassign@@QEAAXXZ(ptr) msvcirt.??_Distream_withassign@@QEAAXXZ
 @ stub -arch=win32 ??_Distrstream@@QAEXXZ
 @ stub -arch=win64 ??_Distrstream@@QEAAXXZ
 @ stub -arch=win32 ??_Dofstream@@QAEXXZ
@@ -407,7 +407,7 @@
 @ thiscall -arch=win32 ??_Eios@@UAEPAXI@Z(ptr long) msvcirt.??_Eios@@UAEPAXI@Z
 @ stub -arch=win32 ??_Eiostream@@UAEPAXI@Z
 @ thiscall -arch=win32 ??_Eistream@@UAEPAXI@Z(ptr long) msvcirt.??_Eistream@@UAEPAXI@Z
-@ stub -arch=win32 ??_Eistream_withassign@@UAEPAXI@Z
+@ thiscall -arch=win32 ??_Eistream_withassign@@UAEPAXI@Z(ptr long) msvcirt.??_Eistream_withassign@@UAEPAXI@Z
 @ stub -arch=win32 ??_Eistrstream@@UAEPAXI@Z
 @ thiscall -arch=win32 ??_Elogic_error@@UAEPAXI@Z(ptr long) msvcirt.??_Elogic_error@@UAEPAXI@Z
 @ stub -arch=win32 ??_Eofstream@@UAEPAXI@Z
@@ -430,7 +430,7 @@
 @ thiscall -arch=win32 ??_Gios@@UAEPAXI@Z(ptr long) msvcirt.??_Gios@@UAEPAXI@Z
 @ stub -arch=win32 ??_Giostream@@UAEPAXI@Z
 @ thiscall -arch=win32 ??_Gistream@@UAEPAXI@Z(ptr long) msvcirt.??_Gistream@@UAEPAXI@Z
-@ stub -arch=win32 ??_Gistream_withassign@@UAEPAXI@Z
+@ thiscall -arch=win32 ??_Gistream_withassign@@UAEPAXI@Z(ptr long) msvcirt.??_Gistream_withassign@@UAEPAXI@Z
 @ stub -arch=win32 ??_Gistrstream@@UAEPAXI@Z
 @ thiscall -arch=win32 ??_Glogic_error@@UAEPAXI@Z(ptr long) msvcirt.??_Glogic_error@@UAEPAXI@Z
 @ stub -arch=win32 ??_Gofstream@@UAEPAXI@Z