diff --git a/Doc/c-api/exceptions.rst b/Doc/c-api/exceptions.rst
index c09b4cf..9fec46f 100644
--- a/Doc/c-api/exceptions.rst
+++ b/Doc/c-api/exceptions.rst
@@ -148,7 +148,8 @@
    This function sets the error indicator and returns *NULL*.  *exception*
    should be a Python exception class.  The *format* and subsequent
    parameters help format the error message; they have the same meaning and
-   values as in :c:func:`PyUnicode_FromFormat`.
+   values as in :c:func:`PyUnicode_FromFormat`. *format* is an ASCII-encoding
+   string.
 
 
 .. c:function:: void PyErr_SetNone(PyObject *type)
@@ -218,7 +219,8 @@
 
    Similar to :c:func:`PyErr_SetFromWindowsErr`, with the additional behavior that
    if *filename* is not *NULL*, it is passed to the constructor of
-   :exc:`WindowsError` as a third parameter. Availability: Windows.
+   :exc:`WindowsError` as a third parameter.  *filename* is decoded from UTF-8.
+   Availability: Windows.
 
 
 .. c:function:: PyObject* PyErr_SetExcFromWindowsErrWithFilename(PyObject *type, int ierr, char *filename)
@@ -232,7 +234,8 @@
    Set file, line, and offset information for the current exception.  If the
    current exception is not a :exc:`SyntaxError`, then it sets additional
    attributes, which make the exception printing subsystem think the exception
-   is a :exc:`SyntaxError`.
+   is a :exc:`SyntaxError`. *filename* is decoded from the filesystem encoding
+   (:func:`sys.getfilesystemencoding`).
 
 .. versionadded:: 3.2
 
@@ -254,7 +257,7 @@
 .. c:function:: int PyErr_WarnEx(PyObject *category, char *message, int stack_level)
 
    Issue a warning message.  The *category* argument is a warning category (see
-   below) or *NULL*; the *message* argument is a message string.  *stack_level* is a
+   below) or *NULL*; the *message* argument is an UTF-8 encoded string.  *stack_level* is a
    positive number giving a number of stack frames; the warning will be issued from
    the  currently executing line of code in that stack frame.  A *stack_level* of 1
    is the function calling :c:func:`PyErr_WarnEx`, 2 is  the function above that,
@@ -294,13 +297,15 @@
    is a straightforward wrapper around the Python function
    :func:`warnings.warn_explicit`, see there for more information.  The *module*
    and *registry* arguments may be set to *NULL* to get the default effect
-   described there.
+   described there. *message*, *filename* and *module* are UTF-8 encoded
+   strings.
 
 
 .. c:function:: int PyErr_WarnFormat(PyObject *category, Py_ssize_t stack_level, const char *format, ...)
 
    Function similar to :c:func:`PyErr_WarnEx`, but use
-   :c:func:`PyUnicode_FromFormat` to format the warning message.
+   :c:func:`PyUnicode_FromFormat` to format the warning message.  *format* is
+   an ASCII-encoded string.
 
    .. versionadded:: 3.2
 
@@ -437,17 +442,19 @@
 .. c:function:: PyObject* PyUnicodeDecodeError_Create(const char *encoding, const char *object, Py_ssize_t length, Py_ssize_t start, Py_ssize_t end, const char *reason)
 
    Create a :class:`UnicodeDecodeError` object with the attributes *encoding*,
-   *object*, *length*, *start*, *end* and *reason*.
+   *object*, *length*, *start*, *end* and *reason*. *encoding* and *reason* are
+   UTF-8 encoded strings.
 
 .. c:function:: PyObject* PyUnicodeEncodeError_Create(const char *encoding, const Py_UNICODE *object, Py_ssize_t length, Py_ssize_t start, Py_ssize_t end, const char *reason)
 
    Create a :class:`UnicodeEncodeError` object with the attributes *encoding*,
-   *object*, *length*, *start*, *end* and *reason*.
+   *object*, *length*, *start*, *end* and *reason*. *encoding* and *reason* are
+   UTF-8 encoded strings.
 
 .. c:function:: PyObject* PyUnicodeTranslateError_Create(const Py_UNICODE *object, Py_ssize_t length, Py_ssize_t start, Py_ssize_t end, const char *reason)
 
    Create a :class:`UnicodeTranslateError` object with the attributes *object*,
-   *length*, *start*, *end* and *reason*.
+   *length*, *start*, *end* and *reason*. *reason* is an UTF-8 encoded string.
 
 .. c:function:: PyObject* PyUnicodeDecodeError_GetEncoding(PyObject *exc)
                 PyObject* PyUnicodeEncodeError_GetEncoding(PyObject *exc)
diff --git a/Include/pyerrors.h b/Include/pyerrors.h
index d72ce07..05c5ea8 100644
--- a/Include/pyerrors.h
+++ b/Include/pyerrors.h
@@ -201,7 +201,9 @@
 PyAPI_FUNC(PyObject *) PyErr_SetFromWindowsErrWithFilenameObject(
     int, const char *);
 PyAPI_FUNC(PyObject *) PyErr_SetFromWindowsErrWithFilename(
-    int, const char *);
+    int ierr,
+    const char *filename        /* decoded from UTF-8 */
+    );
 #ifndef Py_LIMITED_API
 /* XXX redeclare to use WSTRING */
 PyAPI_FUNC(PyObject *) PyErr_SetFromWindowsErrWithUnicodeFilename(
@@ -211,7 +213,10 @@
 PyAPI_FUNC(PyObject *) PyErr_SetExcFromWindowsErrWithFilenameObject(
     PyObject *,int, PyObject *);
 PyAPI_FUNC(PyObject *) PyErr_SetExcFromWindowsErrWithFilename(
-    PyObject *,int, const char *);
+    PyObject *exc,
+    int ierr,
+    const char *filename        /* decoded from UTF-8 */
+    );
 #ifndef Py_LIMITED_API
 PyAPI_FUNC(PyObject *) PyErr_SetExcFromWindowsErrWithUnicodeFilename(
     PyObject *,int, const Py_UNICODE *);
@@ -243,27 +248,51 @@
 #endif
 
 /* Support for adding program text to SyntaxErrors */
-PyAPI_FUNC(void) PyErr_SyntaxLocation(const char *, int);
-PyAPI_FUNC(void) PyErr_SyntaxLocationEx(const char *, int, int);
-PyAPI_FUNC(PyObject *) PyErr_ProgramText(const char *, int);
+PyAPI_FUNC(void) PyErr_SyntaxLocation(
+    const char *filename,       /* decoded from the filesystem encoding */
+    int lineno);
+PyAPI_FUNC(void) PyErr_SyntaxLocationEx(
+    const char *filename,       /* decoded from the filesystem encoding */
+    int lineno,
+    int col_offset);
+PyAPI_FUNC(PyObject *) PyErr_ProgramText(
+    const char *filename,       /* decoded from the filesystem encoding */
+    int lineno);
 
 /* The following functions are used to create and modify unicode
    exceptions from C */
 
 /* create a UnicodeDecodeError object */
 PyAPI_FUNC(PyObject *) PyUnicodeDecodeError_Create(
-    const char *, const char *, Py_ssize_t, Py_ssize_t, Py_ssize_t, const char *);
+    const char *encoding,       /* UTF-8 encoded string */
+    const char *object,
+    Py_ssize_t length,
+    Py_ssize_t start,
+    Py_ssize_t end,
+    const char *reason          /* UTF-8 encoded string */
+    );
 
 /* create a UnicodeEncodeError object */
 #ifndef Py_LIMITED_API
 PyAPI_FUNC(PyObject *) PyUnicodeEncodeError_Create(
-    const char *, const Py_UNICODE *, Py_ssize_t, Py_ssize_t, Py_ssize_t, const char *);
+    const char *encoding,       /* UTF-8 encoded string */
+    const Py_UNICODE *object,
+    Py_ssize_t length,
+    Py_ssize_t start,
+    Py_ssize_t end,
+    const char *reason          /* UTF-8 encoded string */
+    );
 #endif
 
 /* create a UnicodeTranslateError object */
 #ifndef Py_LIMITED_API
 PyAPI_FUNC(PyObject *) PyUnicodeTranslateError_Create(
-    const Py_UNICODE *, Py_ssize_t, Py_ssize_t, Py_ssize_t, const char *);
+    const Py_UNICODE *object,
+    Py_ssize_t length,
+    Py_ssize_t start,
+    Py_ssize_t end,
+    const char *reason          /* UTF-8 encoded string */
+    );
 #endif
 
 /* get the encoding attribute */
@@ -307,11 +336,17 @@
 /* assign a new value to the reason attribute
    return 0 on success, -1 on failure */
 PyAPI_FUNC(int) PyUnicodeEncodeError_SetReason(
-    PyObject *, const char *);
+    PyObject *exc,
+    const char *reason          /* UTF-8 encoded string */
+    );
 PyAPI_FUNC(int) PyUnicodeDecodeError_SetReason(
-    PyObject *, const char *);
+    PyObject *exc,
+    const char *reason          /* UTF-8 encoded string */
+    );
 PyAPI_FUNC(int) PyUnicodeTranslateError_SetReason(
-    PyObject *, const char *);
+    PyObject *exc,
+    const char *reason          /* UTF-8 encoded string */
+    );
 
 
 /* These APIs aren't really part of the error implementation, but
diff --git a/Include/warnings.h b/Include/warnings.h
index 82abb11..7553a25 100644
--- a/Include/warnings.h
+++ b/Include/warnings.h
@@ -8,10 +8,22 @@
 PyAPI_FUNC(PyObject*) _PyWarnings_Init(void);
 #endif
 
-PyAPI_FUNC(int) PyErr_WarnEx(PyObject *, const char *, Py_ssize_t);
-PyAPI_FUNC(int) PyErr_WarnFormat(PyObject *, Py_ssize_t, const char *, ...);
-PyAPI_FUNC(int) PyErr_WarnExplicit(PyObject *, const char *, const char *, int,
-                                    const char *, PyObject *);
+PyAPI_FUNC(int) PyErr_WarnEx(
+    PyObject *category,
+    const char *message,        /* UTF-8 encoded string */
+    Py_ssize_t stack_level);
+PyAPI_FUNC(int) PyErr_WarnFormat(
+    PyObject *category,
+    Py_ssize_t stack_level,
+    const char *format,         /* ASCII-encoded string  */
+    ...);
+PyAPI_FUNC(int) PyErr_WarnExplicit(
+    PyObject *category,
+    const char *message,        /* UTF-8 encoded string */
+    const char *filename,       /* UTF-8 encoded string */
+    int lineno,
+    const char *module,         /* UTF-8 encoded string */
+    PyObject *registry);
 
 /* DEPRECATED: Use PyErr_WarnEx() instead. */
 #ifndef Py_LIMITED_API