diff --git a/Modules/binascii.c b/Modules/binascii.c
index 1f9ff5a..1af6b7f 100644
--- a/Modules/binascii.c
+++ b/Modules/binascii.c
@@ -372,7 +372,7 @@
     if (backtick && !bin_len)
         *ascii_data++ = '`';
     else
-        *ascii_data++ = ' ' + bin_len;
+        *ascii_data++ = ' ' + (unsigned char)bin_len;
 
     for( ; bin_len > 0 || leftbits != 0 ; bin_len--, bin_data++ ) {
         /* Shift the data (or padding) into our buffer */
diff --git a/Modules/zlibmodule.c b/Modules/zlibmodule.c
index cfe7f88..32dd817 100644
--- a/Modules/zlibmodule.c
+++ b/Modules/zlibmodule.c
@@ -142,7 +142,7 @@
 static void
 arrange_input_buffer(z_stream *zst, Py_ssize_t *remains)
 {
-    zst->avail_in = Py_MIN((size_t)*remains, UINT_MAX);
+    zst->avail_in = (uInt)Py_MIN((size_t)*remains, UINT_MAX);
     *remains -= zst->avail_in;
 }
 
@@ -177,7 +177,7 @@
         }
     }
 
-    zst->avail_out = Py_MIN((size_t)(length - occupied), UINT_MAX);
+    zst->avail_out = (uInt)Py_MIN((size_t)(length - occupied), UINT_MAX);
     zst->next_out = (Byte *)PyBytes_AS_STRING(*buffer) + occupied;
 
     return length;
diff --git a/PC/_msi.c b/PC/_msi.c
index 9c3f9f6..c028a88 100644
--- a/PC/_msi.c
+++ b/PC/_msi.c
@@ -948,8 +948,8 @@
 };
 
 #define Py_NOT_PERSIST(x, flag)                        \
-    (x != (int)(flag) &&                      \
-    x != ((int)(flag) | MSIDBOPEN_PATCHFILE))
+    (x != (SIZE_T)(flag) &&                      \
+    x != ((SIZE_T)(flag) | MSIDBOPEN_PATCHFILE))
 
 #define Py_INVALID_PERSIST(x)                \
     (Py_NOT_PERSIST(x, MSIDBOPEN_READONLY) &&  \
@@ -972,7 +972,7 @@
        behavior. */
     if (Py_INVALID_PERSIST(persist))
         return msierror(ERROR_INVALID_PARAMETER);
-    status = MsiOpenDatabase(path, (LPCSTR)persist, &h);
+    status = MsiOpenDatabase(path, (LPCSTR)(SIZE_T)persist, &h);
     if (status != ERROR_SUCCESS)
         return msierror(status);
 
@@ -1038,12 +1038,12 @@
     if (m == NULL)
         return NULL;
 
-    PyModule_AddIntConstant(m, "MSIDBOPEN_CREATEDIRECT", (long)MSIDBOPEN_CREATEDIRECT);
-    PyModule_AddIntConstant(m, "MSIDBOPEN_CREATE", (long)MSIDBOPEN_CREATE);
-    PyModule_AddIntConstant(m, "MSIDBOPEN_DIRECT", (long)MSIDBOPEN_DIRECT);
-    PyModule_AddIntConstant(m, "MSIDBOPEN_READONLY", (long)MSIDBOPEN_READONLY);
-    PyModule_AddIntConstant(m, "MSIDBOPEN_TRANSACT", (long)MSIDBOPEN_TRANSACT);
-    PyModule_AddIntConstant(m, "MSIDBOPEN_PATCHFILE", (long)MSIDBOPEN_PATCHFILE);
+    PyModule_AddIntConstant(m, "MSIDBOPEN_CREATEDIRECT", (long)(SIZE_T)MSIDBOPEN_CREATEDIRECT);
+    PyModule_AddIntConstant(m, "MSIDBOPEN_CREATE", (long)(SIZE_T)MSIDBOPEN_CREATE);
+    PyModule_AddIntConstant(m, "MSIDBOPEN_DIRECT", (long)(SIZE_T)MSIDBOPEN_DIRECT);
+    PyModule_AddIntConstant(m, "MSIDBOPEN_READONLY", (long)(SIZE_T)MSIDBOPEN_READONLY);
+    PyModule_AddIntConstant(m, "MSIDBOPEN_TRANSACT", (long)(SIZE_T)MSIDBOPEN_TRANSACT);
+    PyModule_AddIntConstant(m, "MSIDBOPEN_PATCHFILE", (long)(SIZE_T)MSIDBOPEN_PATCHFILE);
 
     PyModule_AddIntMacro(m, MSICOLINFO_NAMES);
     PyModule_AddIntMacro(m, MSICOLINFO_TYPES);
diff --git a/PC/clinic/msvcrtmodule.c.h b/PC/clinic/msvcrtmodule.c.h
index c6545ac..debd9b0 100644
--- a/PC/clinic/msvcrtmodule.c.h
+++ b/PC/clinic/msvcrtmodule.c.h
@@ -113,13 +113,13 @@
     {"open_osfhandle", (PyCFunction)msvcrt_open_osfhandle, METH_FASTCALL, msvcrt_open_osfhandle__doc__},
 
 static long
-msvcrt_open_osfhandle_impl(PyObject *module, intptr_t handle, int flags);
+msvcrt_open_osfhandle_impl(PyObject *module, void *handle, int flags);
 
 static PyObject *
 msvcrt_open_osfhandle(PyObject *module, PyObject **args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    intptr_t handle;
+    void *handle;
     int flags;
     long _return_value;
 
@@ -148,7 +148,7 @@
 #define MSVCRT_GET_OSFHANDLE_METHODDEF    \
     {"get_osfhandle", (PyCFunction)msvcrt_get_osfhandle, METH_O, msvcrt_get_osfhandle__doc__},
 
-static intptr_t
+static void *
 msvcrt_get_osfhandle_impl(PyObject *module, int fd);
 
 static PyObject *
@@ -156,16 +156,16 @@
 {
     PyObject *return_value = NULL;
     int fd;
-    intptr_t _return_value;
+    void *_return_value;
 
     if (!PyArg_Parse(arg, "i:get_osfhandle", &fd)) {
         goto exit;
     }
     _return_value = msvcrt_get_osfhandle_impl(module, fd);
-    if ((_return_value == -1) && PyErr_Occurred()) {
+    if ((_return_value == NULL || _return_value == INVALID_HANDLE_VALUE) && PyErr_Occurred()) {
         goto exit;
     }
-    return_value = PyLong_FromVoidPtr((void *)_return_value);
+    return_value = PyLong_FromVoidPtr(_return_value);
 
 exit:
     return return_value;
@@ -426,26 +426,26 @@
 #define MSVCRT_CRTSETREPORTFILE_METHODDEF    \
     {"CrtSetReportFile", (PyCFunction)msvcrt_CrtSetReportFile, METH_FASTCALL, msvcrt_CrtSetReportFile__doc__},
 
-static long
-msvcrt_CrtSetReportFile_impl(PyObject *module, int type, int file);
+static void *
+msvcrt_CrtSetReportFile_impl(PyObject *module, int type, void *file);
 
 static PyObject *
 msvcrt_CrtSetReportFile(PyObject *module, PyObject **args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
     int type;
-    int file;
-    long _return_value;
+    void *file;
+    void *_return_value;
 
-    if (!_PyArg_ParseStack(args, nargs, "ii:CrtSetReportFile",
+    if (!_PyArg_ParseStack(args, nargs, "i"_Py_PARSE_INTPTR":CrtSetReportFile",
         &type, &file)) {
         goto exit;
     }
     _return_value = msvcrt_CrtSetReportFile_impl(module, type, file);
-    if ((_return_value == -1) && PyErr_Occurred()) {
+    if ((_return_value == NULL || _return_value == INVALID_HANDLE_VALUE) && PyErr_Occurred()) {
         goto exit;
     }
-    return_value = PyLong_FromLong(_return_value);
+    return_value = PyLong_FromVoidPtr(_return_value);
 
 exit:
     return return_value;
@@ -569,4 +569,4 @@
 #ifndef MSVCRT_SET_ERROR_MODE_METHODDEF
     #define MSVCRT_SET_ERROR_MODE_METHODDEF
 #endif /* !defined(MSVCRT_SET_ERROR_MODE_METHODDEF) */
-/*[clinic end generated code: output=8e9e57c48c4defcc input=a9049054013a1b77]*/
+/*[clinic end generated code: output=e86cf578e7f1ffd2 input=a9049054013a1b77]*/
diff --git a/PC/msvcrtmodule.c b/PC/msvcrtmodule.c
index 59bf54f..fa9ad9d 100644
--- a/PC/msvcrtmodule.c
+++ b/PC/msvcrtmodule.c
@@ -33,14 +33,20 @@
 #endif
 
 /*[python input]
-class intptr_t_converter(CConverter):
-    type = 'intptr_t'
+class HANDLE_converter(CConverter):
+    type = 'void *'
     format_unit = '"_Py_PARSE_INTPTR"'
 
-class handle_return_converter(long_return_converter):
-    type = 'intptr_t'
-    cast = '(void *)'
-    conversion_fn = 'PyLong_FromVoidPtr'
+class HANDLE_return_converter(CReturnConverter):
+    type = 'void *'
+
+    def render(self, function, data):
+        self.declare(data)
+        self.err_occurred_if(
+            "_return_value == NULL || _return_value == INVALID_HANDLE_VALUE",
+            data)
+        data.return_conversion.append(
+            'return_value = PyLong_FromVoidPtr(_return_value);\n')
 
 class byte_char_return_converter(CReturnConverter):
     type = 'int'
@@ -59,7 +65,7 @@
         data.return_conversion.append(
             'return_value = PyUnicode_FromOrdinal(_return_value);\n')
 [python start generated code]*/
-/*[python end generated code: output=da39a3ee5e6b4b0d input=b59f1663dba11997]*/
+/*[python end generated code: output=da39a3ee5e6b4b0d input=2b25dc89e9e59534]*/
 
 /*[clinic input]
 module msvcrt
@@ -152,7 +158,7 @@
 /*[clinic input]
 msvcrt.open_osfhandle -> long
 
-    handle: intptr_t
+    handle: HANDLE
     flags: int
     /
 
@@ -164,13 +170,13 @@
 [clinic start generated code]*/
 
 static long
-msvcrt_open_osfhandle_impl(PyObject *module, intptr_t handle, int flags)
-/*[clinic end generated code: output=cede871bf939d6e3 input=cb2108bbea84514e]*/
+msvcrt_open_osfhandle_impl(PyObject *module, void *handle, int flags)
+/*[clinic end generated code: output=b2fb97c4b515e4e6 input=d5db190a307cf4bb]*/
 {
     int fd;
 
     _Py_BEGIN_SUPPRESS_IPH
-    fd = _open_osfhandle(handle, flags);
+    fd = _open_osfhandle((intptr_t)handle, flags);
     _Py_END_SUPPRESS_IPH
     if (fd == -1)
         PyErr_SetFromErrno(PyExc_OSError);
@@ -179,7 +185,7 @@
 }
 
 /*[clinic input]
-msvcrt.get_osfhandle -> handle
+msvcrt.get_osfhandle -> HANDLE
 
     fd: int
     /
@@ -189,9 +195,9 @@
 Raises OSError if fd is not recognized.
 [clinic start generated code]*/
 
-static intptr_t
+static void *
 msvcrt_get_osfhandle_impl(PyObject *module, int fd)
-/*[clinic end generated code: output=7ce761dd0de2b503 input=305900f4bfab76c7]*/
+/*[clinic end generated code: output=aca01dfe24637374 input=5fcfde9b17136aa2]*/
 {
     intptr_t handle = -1;
 
@@ -201,7 +207,7 @@
     if (handle == -1)
         PyErr_SetFromErrno(PyExc_OSError);
 
-    return handle;
+    return (HANDLE)handle;
 }
 
 /* Console I/O */
@@ -389,10 +395,10 @@
 
 #ifdef _DEBUG
 /*[clinic input]
-msvcrt.CrtSetReportFile -> long
+msvcrt.CrtSetReportFile -> HANDLE
 
     type: int
-    file: int
+    file: HANDLE
     /
 
 Wrapper around _CrtSetReportFile.
@@ -400,14 +406,14 @@
 Only available on Debug builds.
 [clinic start generated code]*/
 
-static long
-msvcrt_CrtSetReportFile_impl(PyObject *module, int type, int file)
-/*[clinic end generated code: output=df291c7fe032eb68 input=bb8f721a604fcc45]*/
+static void *
+msvcrt_CrtSetReportFile_impl(PyObject *module, int type, void *file)
+/*[clinic end generated code: output=9393e8c77088bbe9 input=290809b5f19e65b9]*/
 {
-    long res;
+    HANDLE res;
 
     _Py_BEGIN_SUPPRESS_IPH
-    res = (long)_CrtSetReportFile(type, (_HFILE)file);
+    res = _CrtSetReportFile(type, file);
     _Py_END_SUPPRESS_IPH
 
     return res;
@@ -540,6 +546,20 @@
     }
 }
 
+static void
+insertptr(PyObject *d, char *name, void *value)
+{
+    PyObject *v = PyLong_FromVoidPtr(value);
+    if (v == NULL) {
+        /* Don't bother reporting this error */
+        PyErr_Clear();
+    }
+    else {
+        PyDict_SetItemString(d, name, v);
+        Py_DECREF(v);
+    }
+}
+
 PyMODINIT_FUNC
 PyInit_msvcrt(void)
 {
@@ -568,9 +588,9 @@
     insertint(d, "CRTDBG_MODE_FILE", _CRTDBG_MODE_FILE);
     insertint(d, "CRTDBG_MODE_WNDW", _CRTDBG_MODE_WNDW);
     insertint(d, "CRTDBG_REPORT_MODE", _CRTDBG_REPORT_MODE);
-    insertint(d, "CRTDBG_FILE_STDERR", (int)_CRTDBG_FILE_STDERR);
-    insertint(d, "CRTDBG_FILE_STDOUT", (int)_CRTDBG_FILE_STDOUT);
-    insertint(d, "CRTDBG_REPORT_FILE", (int)_CRTDBG_REPORT_FILE);
+    insertptr(d, "CRTDBG_FILE_STDERR", _CRTDBG_FILE_STDERR);
+    insertptr(d, "CRTDBG_FILE_STDOUT", _CRTDBG_FILE_STDOUT);
+    insertptr(d, "CRTDBG_REPORT_FILE", _CRTDBG_REPORT_FILE);
 #endif
 
     /* constants for the crt versions */
diff --git a/PC/winreg.c b/PC/winreg.c
index 5efdc5e..2d665f7 100644
--- a/PC/winreg.c
+++ b/PC/winreg.c
@@ -905,7 +905,7 @@
     HKEY retKey;
     long rc;
 
-    rc = RegCreateKeyExW(key, sub_key, reserved, NULL, (DWORD)NULL,
+    rc = RegCreateKeyExW(key, sub_key, reserved, NULL, 0,
                          access, NULL, &retKey, NULL);
     if (rc != ERROR_SUCCESS) {
         PyErr_SetFromWindowsErrWithFunction(rc, "CreateKeyEx");
diff --git a/PCbuild/_bz2.vcxproj b/PCbuild/_bz2.vcxproj
index 9efb0d9..b3ab378 100644
--- a/PCbuild/_bz2.vcxproj
+++ b/PCbuild/_bz2.vcxproj
@@ -64,6 +64,7 @@
     <ClCompile>
       <AdditionalIncludeDirectories>$(bz2Dir);%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
       <PreprocessorDefinitions>WIN32;_FILE_OFFSET_BITS=64;_CRT_SECURE_NO_DEPRECATE;_CRT_NONSTDC_NO_DEPRECATE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <DisableSpecificWarnings>4244;4267;%(DisableSpecificWarnings)</DisableSpecificWarnings>
     </ClCompile>
     <Link>
       <BaseAddress>0x1D170000</BaseAddress>
diff --git a/PCbuild/_ctypes.vcxproj b/PCbuild/_ctypes.vcxproj
index 70bea45..43d51f8 100644
--- a/PCbuild/_ctypes.vcxproj
+++ b/PCbuild/_ctypes.vcxproj
@@ -83,7 +83,9 @@
     <ClCompile Include="..\Modules\_ctypes\cfield.c" />
     <ClCompile Include="..\Modules\_ctypes\libffi_msvc\ffi.c" />
     <ClCompile Include="..\Modules\_ctypes\malloc_closure.c" />
-    <ClCompile Include="..\Modules\_ctypes\libffi_msvc\prep_cif.c" />
+    <ClCompile Include="..\Modules\_ctypes\libffi_msvc\prep_cif.c">
+      <DisableSpecificWarnings Condition="'$(Platform)'=='x64'">4267;%(DisableSpecificWarnings)</DisableSpecificWarnings>
+    </ClCompile>
     <ClCompile Include="..\Modules\_ctypes\stgdict.c" />
     <ClCompile Include="..\Modules\_ctypes\libffi_msvc\win32.c">
       <ExcludedFromBuild Condition="'$(Platform)'=='x64'">true</ExcludedFromBuild>
diff --git a/PCbuild/liblzma.vcxproj b/PCbuild/liblzma.vcxproj
index 4ace9d9..f408b54 100644
--- a/PCbuild/liblzma.vcxproj
+++ b/PCbuild/liblzma.vcxproj
@@ -64,7 +64,7 @@
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Disabled</Optimization>
       <AdditionalIncludeDirectories>$(lzmaDir)windows;$(lzmaDir)src/liblzma/common;$(lzmaDir)src/common;$(lzmaDir)src/liblzma/api;$(lzmaDir)src/liblzma/check;$(lzmaDir)src/liblzma/delta;$(lzmaDir)src/liblzma/lz;$(lzmaDir)src/liblzma/lzma;$(lzmaDir)src/liblzma/rangecoder;$(lzmaDir)src/liblzma/simple</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4028;4113;4244;4267;4996</DisableSpecificWarnings>
+      <DisableSpecificWarnings>4028;4113;4133;4244;4267;4996;%(DisableSpecificWarnings)</DisableSpecificWarnings>
     </ClCompile>
   </ItemDefinitionGroup>
   <ItemGroup>
diff --git a/PCbuild/tcl.vcxproj b/PCbuild/tcl.vcxproj
index 28a0ee9..c940ab1 100644
--- a/PCbuild/tcl.vcxproj
+++ b/PCbuild/tcl.vcxproj
@@ -55,11 +55,12 @@
     <TclOpts Condition="$(Configuration) == 'Debug'">symbols,msvcrt</TclOpts>
     <TclDirs>INSTALLDIR="$(OutDir.TrimEnd(`\`))" INSTALL_DIR="$(OutDir.TrimEnd(`\`))"</TclDirs>
     <DebugFlags Condition="'$(Configuration)' == 'Debug'">DEBUGFLAGS="-wd4456 -wd4457 -wd4458 -wd4459 -wd4996"</DebugFlags>
+    <WarningsFlags>WARNINGS="-W3 -wd4311 -wd4312"</WarningsFlags>
     <NMakeBuildCommandLine>setlocal
 set VCINSTALLDIR=$(VCInstallDir)
 cd /D "$(tclDir)win"
-nmake -f makefile.vc MACHINE=$(TclMachine) OPTS=$(TclOpts) $(TclDirs) $(DebugFlags) core shell dlls
-nmake -f makefile.vc MACHINE=$(TclMachine) OPTS=$(TclOpts) $(TclDirs) $(DebugFlags) install-binaries install-libraries
+nmake -f makefile.vc MACHINE=$(TclMachine) OPTS=$(TclOpts) $(TclDirs) $(DebugFlags) $(WarningsFlags) core shell dlls
+nmake -f makefile.vc MACHINE=$(TclMachine) OPTS=$(TclOpts) $(TclDirs) $(DebugFlags) $(WarningsFlags) install-binaries install-libraries
 copy /Y ..\license.terms "$(OutDir)\tcllicense.terms"
 </NMakeBuildCommandLine>
   </PropertyGroup>
diff --git a/PCbuild/tix.vcxproj b/PCbuild/tix.vcxproj
index 525758c..5168209 100644
--- a/PCbuild/tix.vcxproj
+++ b/PCbuild/tix.vcxproj
@@ -56,7 +56,7 @@
     <TixDirs>BUILDDIRTOP="$(BuildDirTop)" TCL_DIR="$(tclDir.TrimEnd(`\`))" TK_DIR="$(tkDir.TrimEnd(`\`))" INSTALL_DIR="$(OutDir.TrimEnd(`\`))"</TixDirs>
     <DebugFlags Condition="'$(Configuration)' == 'Debug'">DEBUG=1 NODEBUG=0 TCL_DBGX=g TK_DBGX=g</DebugFlags>
     <DebugFlags Condition="'$(Configuration)' != 'Debug'">DEBUG=0 NODEBUG=1</DebugFlags>
-    <CFlags>-c -W3 -nologo -MD -wd4028 -wd4090</CFlags>
+    <CFlags>-c -W3 -nologo -MD -wd4028 -wd4090 -wd4244 -wd4267 -wd4312</CFlags>
     <NMakeBuildCommandLine>setlocal
 set VCINSTALLDIR=$(VCInstallDir)
 cd /D "$(tixDir)win"
diff --git a/PCbuild/tk.vcxproj b/PCbuild/tk.vcxproj
index f90e482..a1b8b9e 100644
--- a/PCbuild/tk.vcxproj
+++ b/PCbuild/tk.vcxproj
@@ -56,11 +56,12 @@
     <TkOpts Condition="$(Configuration) == 'Debug'">symbols,msvcrt</TkOpts>
     <TkDirs>TCLDIR="$(tclDir.TrimEnd(`\`))" INSTALLDIR="$(OutDir.TrimEnd(`\`))"</TkDirs>
     <DebugFlags Condition="'$(Configuration)' == 'Debug'">DEBUGFLAGS="-wd4456 -wd4457 -wd4458 -wd4459 -wd4996"</DebugFlags>
+    <WarningsFlags>WARNINGS="-W3 -wd4244 -wd4267 -wd4311 -wd4312 -wd4334"</WarningsFlags>
     <NMakeBuildCommandLine>setlocal
 set VCINSTALLDIR=$(VCInstallDir)
 cd /D "$(tkDir)win"
-nmake /nologo -f makefile.vc RC=rc MACHINE=$(TclMachine) OPTS=$(TkOpts) $(TkDirs) $(DebugFlags) all
-nmake /nologo -f makefile.vc RC=rc MACHINE=$(TclMachine) OPTS=$(TkOpts) $(TkDirs) $(DebugFlags) install-binaries install-libraries
+nmake /nologo -f makefile.vc RC=rc MACHINE=$(TclMachine) OPTS=$(TkOpts) $(TkDirs) $(DebugFlags) $(WarningsFlags) all
+nmake /nologo -f makefile.vc RC=rc MACHINE=$(TclMachine) OPTS=$(TkOpts) $(TkDirs) $(DebugFlags) $(WarningsFlags) install-binaries install-libraries
 copy /Y ..\license.terms "$(OutDir)\tklicense.terms"
 </NMakeBuildCommandLine>
   </PropertyGroup>