bpo-39943: Add the const qualifier to pointers on non-mutable PyUnicode data. (GH-19345)

Modules/_csv.c

@@ -789,7 +789,7 @@ Reader_iternext(ReaderObj *self)
     Py_UCS4 c;
     Py_ssize_t pos, linelen;
     unsigned int kind;
-    void *data;
+    const void *data;
     PyObject *lineobj;
 
     if (parse_reset(self) < 0)
@@ -996,7 +996,7 @@ join_reset(WriterObj *self)
  * record length.
  */
 static Py_ssize_t
-join_append_data(WriterObj *self, unsigned int field_kind, void *field_data,
+join_append_data(WriterObj *self, unsigned int field_kind, const void *field_data,
                  Py_ssize_t field_len, int *quoted,
                  int copy_phase)
 {
@@ -1107,7 +1107,7 @@ static int
 join_append(WriterObj *self, PyObject *field, int quoted)
 {
     unsigned int field_kind = -1;
-    void *field_data = NULL;
+    const void *field_data = NULL;
     Py_ssize_t field_len = 0;
     Py_ssize_t rec_len;
 
@@ -1139,7 +1139,7 @@ join_append_lineterminator(WriterObj *self)
 {
     Py_ssize_t terminator_len, i;
     unsigned int term_kind;
-    void *term_data;
+    const void *term_data;
 
     terminator_len = PyUnicode_GET_LENGTH(self->dialect->lineterminator);
     if (terminator_len == -1)

Modules/_decimal/_decimal.c

@@ -1878,7 +1878,7 @@ dec_dealloc(PyObject *dec)
 /******************************************************************************/
 
 Py_LOCAL_INLINE(int)
-is_space(enum PyUnicode_Kind kind, void *data, Py_ssize_t pos)
+is_space(enum PyUnicode_Kind kind, const void *data, Py_ssize_t pos)
 {
     Py_UCS4 ch = PyUnicode_READ(kind, data, pos);
     return Py_UNICODE_ISSPACE(ch);
@@ -1896,7 +1896,7 @@ static char *
 numeric_as_ascii(const PyObject *u, int strip_ws, int ignore_underscores)
 {
     enum PyUnicode_Kind kind;
-    void *data;
+    const void *data;
     Py_UCS4 ch;
     char *res, *cp;
     Py_ssize_t j, len;

Modules/_elementtree.c

@@ -1132,7 +1132,7 @@ checkpath(PyObject* tag)
 
     if (PyUnicode_Check(tag)) {
         const Py_ssize_t len = PyUnicode_GET_LENGTH(tag);
-        void *data = PyUnicode_DATA(tag);
+        const void *data = PyUnicode_DATA(tag);
         unsigned int kind = PyUnicode_KIND(tag);
         if (len >= 3 && PyUnicode_READ(kind, data, 0) == '{' && (
                 PyUnicode_READ(kind, data, 1) == '}' || (

Modules/_io/textio.c

@@ -340,7 +340,7 @@ _PyIncrementalNewlineDecoder_decode(PyObject *myself,
             goto error;
         kind = PyUnicode_KIND(modified);
         out = PyUnicode_DATA(modified);
-        PyUnicode_WRITE(kind, PyUnicode_DATA(modified), 0, '\r');
+        PyUnicode_WRITE(kind, out, 0, '\r');
         memcpy(out + kind, PyUnicode_DATA(output), kind * output_len);
         Py_DECREF(output);
         output = modified; /* output remains ready */
@@ -367,7 +367,7 @@ _PyIncrementalNewlineDecoder_decode(PyObject *myself,
     /* Record which newlines are read and do newline translation if desired,
        all in one pass. */
     {
-        void *in_str;
+        const void *in_str;
         Py_ssize_t len;
         int seennl = self->seennl;
         int only_lf = 0;
@@ -447,7 +447,7 @@ _PyIncrementalNewlineDecoder_decode(PyObject *myself,
         else {
             void *translated;
             int kind = PyUnicode_KIND(output);
-            void *in_str = PyUnicode_DATA(output);
+            const void *in_str = PyUnicode_DATA(output);
             Py_ssize_t in, out;
             /* XXX: Previous in-place translation here is disabled as
                resizing is not possible anymore */
@@ -2085,7 +2085,7 @@ _PyIO_find_line_ending(
     else {
         /* Non-universal mode. */
         Py_ssize_t readnl_len = PyUnicode_GET_LENGTH(readnl);
-        Py_UCS1 *nl = PyUnicode_1BYTE_DATA(readnl);
+        const Py_UCS1 *nl = PyUnicode_1BYTE_DATA(readnl);
         /* Assume that readnl is an ASCII character. */
         assert(PyUnicode_KIND(readnl) == PyUnicode_1BYTE_KIND);
         if (readnl_len == 1) {
@@ -2139,7 +2139,7 @@ _textiowrapper_readline(textio *self, Py_ssize_t limit)
     chunked = 0;
 
     while (1) {
-        char *ptr;
+        const char *ptr;
         Py_ssize_t line_len;
         int kind;
         Py_ssize_t consumed = 0;

Modules/_json.c

@@ -159,8 +159,8 @@ ascii_escape_unicode(PyObject *pystr)
     Py_ssize_t output_size;
     Py_ssize_t chars;
     PyObject *rval;
-    void *input;
+    const void *input;
-    unsigned char *output;
+    Py_UCS1 *output;
     int kind;
 
     if (PyUnicode_READY(pystr) == -1)
@@ -225,7 +225,7 @@ escape_unicode(PyObject *pystr)
     Py_ssize_t output_size;
     Py_ssize_t chars;
     PyObject *rval;
-    void *input;
+    const void *input;
     int kind;
     Py_UCS4 maxchar;
 
@@ -678,7 +678,7 @@ _parse_object_unicode(PyScannerObject *s, PyObject *pystr, Py_ssize_t idx, Py_ss
 
     Returns a new PyObject (usually a dict, but object_hook can change that)
     */
-    void *str;
+    const void *str;
     int kind;
     Py_ssize_t end_idx;
     PyObject *val = NULL;
@@ -808,7 +808,7 @@ _parse_array_unicode(PyScannerObject *s, PyObject *pystr, Py_ssize_t idx, Py_ssi
 
     Returns a new PyList
     */
-    void *str;
+    const void *str;
     int kind;
     Py_ssize_t end_idx;
     PyObject *val = NULL;
@@ -911,7 +911,7 @@ _match_number_unicode(PyScannerObject *s, PyObject *pystr, Py_ssize_t start, Py_
         PyLong, or PyFloat.
         May return other types if parse_int or parse_float are set
     */
-    void *str;
+    const void *str;
     int kind;
     Py_ssize_t end_idx;
     Py_ssize_t idx = start;
@@ -1028,7 +1028,7 @@ scan_once_unicode(PyScannerObject *s, PyObject *pystr, Py_ssize_t idx, Py_ssize_
     Returns a new PyObject representation of the term.
     */
     PyObject *res;
-    void *str;
+    const void *str;
     int kind;
     Py_ssize_t length;
 

Modules/_operator.c

@@ -1170,7 +1170,7 @@ attrgetter_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
     for (idx = 0; idx < nattrs; ++idx) {
         PyObject *item = PyTuple_GET_ITEM(args, idx);
         Py_ssize_t item_len;
-        void *data;
+        const void *data;
         unsigned int kind;
         int dot_count;
 

Modules/_pickle.c

@@ -2581,7 +2581,7 @@ raw_unicode_escape(PyObject *obj)
 {
     char *p;
     Py_ssize_t i, size;
-    void *data;
+    const void *data;
     unsigned int kind;
     _PyBytesWriter writer;
 

Modules/_sqlite/connection.c

@@ -1644,7 +1644,7 @@ pysqlite_connection_create_collation(pysqlite_Connection* self, PyObject* args)
     const char *uppercase_name_str;
     int rc;
     unsigned int kind;
-    void *data;
+    const void *data;
 
     if (!pysqlite_check_thread(self) || !pysqlite_check_connection(self)) {
         goto finally;

Modules/_sre.c

@@ -351,7 +351,7 @@ state_reset(SRE_STATE* state)
     data_stack_dealloc(state);
 }
 
-static void*
+static const void*
 getstring(PyObject* string, Py_ssize_t* p_length,
           int* p_isbytes, int* p_charsize,
           Py_buffer *view)
@@ -398,11 +398,11 @@ state_init(SRE_STATE* state, PatternObject* pattern, PyObject* string,
 
     Py_ssize_t length;
     int isbytes, charsize;
-    void* ptr;
+    const void* ptr;
 
     memset(state, 0, sizeof(SRE_STATE));
 
-    state->mark = PyMem_New(void *, pattern->groups * 2);
+    state->mark = PyMem_New(const void *, pattern->groups * 2);
     if (!state->mark) {
         PyErr_NoMemory();
         goto err;
@@ -891,7 +891,7 @@ _sre_SRE_Pattern_split_impl(PatternObject *self, PyObject *string,
     Py_ssize_t status;
     Py_ssize_t n;
     Py_ssize_t i;
-    void* last;
+    const void* last;
 
     assert(self->codesize != 0);
 
@@ -984,7 +984,7 @@ pattern_subx(PatternObject* self, PyObject* ptemplate, PyObject* string,
     PyObject* item;
     PyObject* filter;
     PyObject* match;
-    void* ptr;
+    const void* ptr;
     Py_ssize_t status;
     Py_ssize_t n;
     Py_ssize_t i, b, e;
@@ -1895,7 +1895,7 @@ match_getslice_by_index(MatchObject* self, Py_ssize_t index, PyObject* def)
     int isbytes, charsize;
     Py_buffer view;
     PyObject *result;
-    void* ptr;
+    const void* ptr;
     Py_ssize_t i, j;
 
     assert(0 <= index && index < self->groups);

Modules/cjkcodecs/cjkcodecs.h

@@ -72,7 +72,7 @@ static const struct dbcs_map *mapping_list;
 #define ENCODER(encoding)                                               \
     static Py_ssize_t encoding##_encode(                                \
         MultibyteCodec_State *state, const void *config,                \
-        int kind, void *data,                          \
+        int kind, const void *data,                                     \
         Py_ssize_t *inpos, Py_ssize_t inlen,                            \
         unsigned char **outbuf, Py_ssize_t outleft, int flags)
 #define ENCODER_RESET(encoding)                                         \

Modules/cjkcodecs/multibytecodec.c

@@ -228,7 +228,7 @@ multibytecodec_encerror(MultibyteCodec *codec,
         Py_ssize_t r;
         Py_ssize_t inpos;
         int kind;
-        void *data;
+        const void *data;
 
         replchar = PyUnicode_FromOrdinal('?');
         if (replchar == NULL)
@@ -457,7 +457,7 @@ multibytecodec_encode(MultibyteCodec *codec,
     Py_ssize_t finalsize, r = 0;
     Py_ssize_t datalen;
     int kind;
-    void *data;
+    const void *data;
 
     if (PyUnicode_READY(text) < 0)
         return NULL;

Modules/cjkcodecs/multibytecodec.h

@@ -30,7 +30,7 @@ typedef struct {
 typedef int (*mbcodec_init)(const void *config);
 typedef Py_ssize_t (*mbencode_func)(MultibyteCodec_State *state,
                         const void *config,
-                        int kind, void *data,
+                        int kind, const void *data,
                         Py_ssize_t *inpos, Py_ssize_t inlen,
                         unsigned char **outbuf, Py_ssize_t outleft,
                         int flags);

Modules/pyexpat.c

@@ -1060,7 +1060,7 @@ PyUnknownEncodingHandler(void *encodingHandlerData,
     static unsigned char template_buffer[256] = {0};
     PyObject* u;
     int i;
-    void *data;
+    const void *data;
     unsigned int kind;
 
     if (PyErr_Occurred())

Modules/sre.h

@@ -54,17 +54,17 @@ typedef struct {
 
 typedef struct SRE_REPEAT_T {
     Py_ssize_t count;
-    SRE_CODE* pattern; /* points to REPEAT operator arguments */
+    const SRE_CODE* pattern; /* points to REPEAT operator arguments */
-    void* last_ptr; /* helper to check for infinite loops */
+    const void* last_ptr; /* helper to check for infinite loops */
     struct SRE_REPEAT_T *prev; /* points to previous repeat context */
 } SRE_REPEAT;
 
 typedef struct {
     /* string pointers */
-    void* ptr; /* current position (also end of current slice) */
+    const void* ptr; /* current position (also end of current slice) */
-    void* beginning; /* start of original string */
+    const void* beginning; /* start of original string */
-    void* start; /* start of current slice */
+    const void* start; /* start of current slice */
-    void* end; /* end of original string */
+    const void* end; /* end of original string */
     /* attributes for the match object */
     PyObject* string;
     Py_buffer buffer;
@@ -74,7 +74,7 @@ typedef struct {
     /* registers */
     Py_ssize_t lastindex;
     Py_ssize_t lastmark;
-    void** mark;
+    const void** mark;
     int match_all;
     int must_advance;
     /* dynamically allocated stuff */

Modules/sre_lib.h

@@ -13,7 +13,7 @@
 /* This file is included three times, with different character settings */
 
 LOCAL(int)
-SRE(at)(SRE_STATE* state, SRE_CHAR* ptr, SRE_CODE at)
+SRE(at)(SRE_STATE* state, const SRE_CHAR* ptr, SRE_CODE at)
 {
     /* check if pointer is at given position */
 
@@ -101,7 +101,7 @@ SRE(at)(SRE_STATE* state, SRE_CHAR* ptr, SRE_CODE at)
 }
 
 LOCAL(int)
-SRE(charset)(SRE_STATE* state, SRE_CODE* set, SRE_CODE ch)
+SRE(charset)(SRE_STATE* state, const SRE_CODE* set, SRE_CODE ch)
 {
     /* check if character is a member of the given set */
 
@@ -188,7 +188,7 @@ SRE(charset)(SRE_STATE* state, SRE_CODE* set, SRE_CODE ch)
 }
 
 LOCAL(int)
-SRE(charset_loc_ignore)(SRE_STATE* state, SRE_CODE* set, SRE_CODE ch)
+SRE(charset_loc_ignore)(SRE_STATE* state, const SRE_CODE* set, SRE_CODE ch)
 {
     SRE_CODE lo, up;
     lo = sre_lower_locale(ch);
@@ -199,15 +199,15 @@ SRE(charset_loc_ignore)(SRE_STATE* state, SRE_CODE* set, SRE_CODE ch)
     return up != lo && SRE(charset)(state, set, up);
 }
 
-LOCAL(Py_ssize_t) SRE(match)(SRE_STATE* state, SRE_CODE* pattern, int toplevel);
+LOCAL(Py_ssize_t) SRE(match)(SRE_STATE* state, const SRE_CODE* pattern, int toplevel);
 
 LOCAL(Py_ssize_t)
-SRE(count)(SRE_STATE* state, SRE_CODE* pattern, Py_ssize_t maxcount)
+SRE(count)(SRE_STATE* state, const SRE_CODE* pattern, Py_ssize_t maxcount)
 {
     SRE_CODE chr;
     SRE_CHAR c;
-    SRE_CHAR* ptr = (SRE_CHAR *)state->ptr;
+    const SRE_CHAR* ptr = (const SRE_CHAR *)state->ptr;
-    SRE_CHAR* end = (SRE_CHAR *)state->end;
+    const SRE_CHAR* end = (const SRE_CHAR *)state->end;
     Py_ssize_t i;
 
     /* adjust end */
@@ -335,14 +335,14 @@ SRE(count)(SRE_STATE* state, SRE_CODE* pattern, Py_ssize_t maxcount)
 
 #if 0 /* not used in this release */
 LOCAL(int)
-SRE(info)(SRE_STATE* state, SRE_CODE* pattern)
+SRE(info)(SRE_STATE* state, const SRE_CODE* pattern)
 {
     /* check if an SRE_OP_INFO block matches at the current position.
        returns the number of SRE_CODE objects to skip if successful, 0
        if no match */
 
-    SRE_CHAR* end = (SRE_CHAR*) state->end;
+    const SRE_CHAR* end = (const SRE_CHAR*) state->end;
-    SRE_CHAR* ptr = (SRE_CHAR*) state->ptr;
+    const SRE_CHAR* ptr = (const SRE_CHAR*) state->ptr;
     Py_ssize_t i;
 
     /* check minimal length */
@@ -531,8 +531,8 @@ do { \
 typedef struct {
     Py_ssize_t last_ctx_pos;
     Py_ssize_t jump;
-    SRE_CHAR* ptr;
+    const SRE_CHAR* ptr;
-    SRE_CODE* pattern;
+    const SRE_CODE* pattern;
     Py_ssize_t count;
     Py_ssize_t lastmark;
     Py_ssize_t lastindex;
@@ -546,9 +546,9 @@ typedef struct {
 /* check if string matches the given pattern.  returns <0 for
    error, 0 for failure, and 1 for success */
 LOCAL(Py_ssize_t)
-SRE(match)(SRE_STATE* state, SRE_CODE* pattern, int toplevel)
+SRE(match)(SRE_STATE* state, const SRE_CODE* pattern, int toplevel)
 {
-    SRE_CHAR* end = (SRE_CHAR *)state->end;
+    const SRE_CHAR* end = (const SRE_CHAR *)state->end;
     Py_ssize_t alloc_pos, ctx_pos = -1;
     Py_ssize_t i, ret = 0;
     Py_ssize_t jump;

Modules/unicodedata.c

@@ -496,7 +496,7 @@ nfd_nfkd(PyObject *self, PyObject *input, int k)
     Py_UCS4 *output;
     Py_ssize_t i, o, osize;
     int kind;
-    void *data;
+    const void *data;
     /* Longest decomposition in Unicode 3.2: U+FDFA */
     Py_UCS4 stack[20];
     Py_ssize_t space, isize;
@@ -643,7 +643,7 @@ nfc_nfkc(PyObject *self, PyObject *input, int k)
 {
     PyObject *result;
     int kind;
-    void *data;
+    const void *data;
     Py_UCS4 *output;
     Py_ssize_t i, i1, o, len;
     int f,l,index,index1,comb;
@@ -804,7 +804,7 @@ is_normalized_quickcheck(PyObject *self, PyObject *input,
 
     Py_ssize_t i, len;
     int kind;
-    void *data;
+    const void *data;
     unsigned char prev_combining = 0;
 
     /* The two quickcheck bits at this shift have type QuickcheckResult. */

Objects/bytesobject.c

@@ -1265,12 +1265,14 @@ PyBytes_Repr(PyObject *obj, int smartquotes)
     Py_ssize_t i, length = Py_SIZE(op);
     Py_ssize_t newsize, squotes, dquotes;
     PyObject *v;
-    unsigned char quote, *s, *p;
+    unsigned char quote;
+    const unsigned char *s;
+    Py_UCS1 *p;
 
     /* Compute size of output string */
     squotes = dquotes = 0;
     newsize = 3; /* b'' */
-    s = (unsigned char*)op->ob_sval;
+    s = (const unsigned char*)op->ob_sval;
     for (i = 0; i < length; i++) {
         Py_ssize_t incr = 1;
         switch(s[i]) {
@@ -2271,7 +2273,7 @@ _PyBytes_FromHex(PyObject *string, int use_bytearray)
     char *buf;
     Py_ssize_t hexlen, invalid_char;
     unsigned int top, bot;
-    Py_UCS1 *str, *end;
+    const Py_UCS1 *str, *end;
     _PyBytesWriter writer;
 
     _PyBytesWriter_Init(&writer);
@@ -2283,7 +2285,7 @@ _PyBytes_FromHex(PyObject *string, int use_bytearray)
     hexlen = PyUnicode_GET_LENGTH(string);
 
     if (!PyUnicode_IS_ASCII(string)) {
-        void *data = PyUnicode_DATA(string);
+        const void *data = PyUnicode_DATA(string);
         unsigned int kind = PyUnicode_KIND(string);
         Py_ssize_t i;
 

Objects/exceptions.c

@@ -1428,7 +1428,7 @@ my_basename(PyObject *name)
 {
     Py_ssize_t i, size, offset;
     int kind;
-    void *data;
+    const void *data;
 
     if (PyUnicode_READY(name))
         return NULL;
@@ -2953,7 +2953,7 @@ _check_for_legacy_statements(PySyntaxErrorObject *self, Py_ssize_t start)
     static PyObject *exec_prefix = NULL;
     Py_ssize_t text_len = PyUnicode_GET_LENGTH(self->text), match;
     int kind = PyUnicode_KIND(self->text);
-    void *data = PyUnicode_DATA(self->text);
+    const void *data = PyUnicode_DATA(self->text);
 
     /* Ignore leading whitespace */
     while (start < text_len) {

Objects/stringlib/codecs.h

@@ -259,7 +259,7 @@ InvalidContinuation3:
 Py_LOCAL_INLINE(char *)
 STRINGLIB(utf8_encoder)(_PyBytesWriter *writer,
                         PyObject *unicode,
-                        STRINGLIB_CHAR *data,
+                        const STRINGLIB_CHAR *data,
                         Py_ssize_t size,
                         _Py_error_handler error_handler,
                         const char *errors)

Objects/typeobject.c

@@ -3208,7 +3208,7 @@ is_dunder_name(PyObject *name)
     int kind = PyUnicode_KIND(name);
     /* Special names contain at least "__x__" and are always ASCII. */
     if (length > 4 && kind == PyUnicode_1BYTE_KIND) {
-        Py_UCS1 *characters = PyUnicode_1BYTE_DATA(name);
+        const Py_UCS1 *characters = PyUnicode_1BYTE_DATA(name);
         return (
             ((characters[length-2] == '_') && (characters[length-1] == '_')) &&
             ((characters[0] == '_') && (characters[1] == '_'))

Objects/unicodeobject.c

@@ -578,7 +578,7 @@ _PyUnicode_CheckConsistency(PyObject *op, int check_content)
     if (check_content && kind != PyUnicode_WCHAR_KIND) {
         Py_ssize_t i;
         Py_UCS4 maxchar = 0;
-        void *data;
+        const void *data;
         Py_UCS4 ch;
 
         data = PyUnicode_DATA(ascii);
@@ -662,7 +662,7 @@ unicode_result_ready(PyObject *unicode)
     }
 
     if (length == 1) {
-        void *data = PyUnicode_DATA(unicode);
+        const void *data = PyUnicode_DATA(unicode);
         int kind = PyUnicode_KIND(unicode);
         Py_UCS4 ch = PyUnicode_READ(kind, data, 0);
         if (ch < 256) {
@@ -720,7 +720,7 @@ backslashreplace(_PyBytesWriter *writer, char *str,
     Py_ssize_t size, i;
     Py_UCS4 ch;
     enum PyUnicode_Kind kind;
-    void *data;
+    const void *data;
 
     assert(PyUnicode_IS_READY(unicode));
     kind = PyUnicode_KIND(unicode);
@@ -787,7 +787,7 @@ xmlcharrefreplace(_PyBytesWriter *writer, char *str,
     Py_ssize_t size, i;
     Py_UCS4 ch;
     enum PyUnicode_Kind kind;
-    void *data;
+    const void *data;
 
     assert(PyUnicode_IS_READY(unicode));
     kind = PyUnicode_KIND(unicode);
@@ -863,7 +863,7 @@ static BLOOM_MASK bloom_linebreak = ~(BLOOM_MASK)0;
      (BLOOM(bloom_linebreak, (ch)) && Py_UNICODE_ISLINEBREAK(ch)))
 
 static inline BLOOM_MASK
-make_bloom_mask(int kind, void* ptr, Py_ssize_t len)
+make_bloom_mask(int kind, const void* ptr, Py_ssize_t len)
 {
 #define BLOOM_UPDATE(TYPE, MASK, PTR, LEN)             \
     do {                                               \
@@ -1302,16 +1302,16 @@ unicode_kind_name(PyObject *unicode)
 
 #ifdef Py_DEBUG
 /* Functions wrapping macros for use in debugger */
-char *_PyUnicode_utf8(void *unicode_raw){
+const char *_PyUnicode_utf8(void *unicode_raw){
     PyObject *unicode = _PyObject_CAST(unicode_raw);
     return PyUnicode_UTF8(unicode);
 }
 
-void *_PyUnicode_compact_data(void *unicode_raw) {
+const void *_PyUnicode_compact_data(void *unicode_raw) {
     PyObject *unicode = _PyObject_CAST(unicode_raw);
     return _PyUnicode_COMPACT_DATA(unicode);
 }
-void *_PyUnicode_data(void *unicode_raw) {
+const void *_PyUnicode_data(void *unicode_raw) {
     PyObject *unicode = _PyObject_CAST(unicode_raw);
     printf("obj %p\n", (void*)unicode);
     printf("compact %d\n", PyUnicode_IS_COMPACT(unicode));
@@ -1328,7 +1328,7 @@ _PyUnicode_Dump(PyObject *op)
     PyASCIIObject *ascii = (PyASCIIObject *)op;
     PyCompactUnicodeObject *compact = (PyCompactUnicodeObject *)op;
     PyUnicodeObject *unicode = (PyUnicodeObject *)op;
-    void *data;
+    const void *data;
 
     if (ascii->state.compact)
     {
@@ -1528,7 +1528,8 @@ _copy_characters(PyObject *to, Py_ssize_t to_start,
                  Py_ssize_t how_many, int check_maxchar)
 {
     unsigned int from_kind, to_kind;
-    void *from_data, *to_data;
+    const void *from_data;
+    void *to_data;
 
     assert(0 <= how_many);
     assert(0 <= from_start);
@@ -1553,7 +1554,7 @@ _copy_characters(PyObject *to, Py_ssize_t to_start,
     if (!check_maxchar
         && PyUnicode_MAX_CHAR_VALUE(from) > PyUnicode_MAX_CHAR_VALUE(to))
     {
-        const Py_UCS4 to_maxchar = PyUnicode_MAX_CHAR_VALUE(to);
+        Py_UCS4 to_maxchar = PyUnicode_MAX_CHAR_VALUE(to);
         Py_UCS4 ch;
         Py_ssize_t i;
         for (i=0; i < how_many; i++) {
@@ -1571,12 +1572,12 @@ _copy_characters(PyObject *to, Py_ssize_t to_start,
                check that all written characters are pure ASCII */
             Py_UCS4 max_char;
             max_char = ucs1lib_find_max_char(from_data,
-                                             (Py_UCS1*)from_data + how_many);
+                                             (const Py_UCS1*)from_data + how_many);
             if (max_char >= 128)
                 return -1;
         }
         memcpy((char*)to_data + to_kind * to_start,
-                  (char*)from_data + from_kind * from_start,
+                  (const char*)from_data + from_kind * from_start,
                   to_kind * how_many);
     }
     else if (from_kind == PyUnicode_1BYTE_KIND
@@ -2047,7 +2048,7 @@ unicode_write_cstr(PyObject *unicode, Py_ssize_t index,
                    const char *str, Py_ssize_t len)
 {
     enum PyUnicode_Kind kind = PyUnicode_KIND(unicode);
-    void *data = PyUnicode_DATA(unicode);
+    const void *data = PyUnicode_DATA(unicode);
     const char *end = str + len;
 
     assert(index + len <= PyUnicode_GET_LENGTH(unicode));
@@ -2402,7 +2403,7 @@ Py_UCS4
 _PyUnicode_FindMaxChar(PyObject *unicode, Py_ssize_t start, Py_ssize_t end)
 {
     enum PyUnicode_Kind kind;
-    void *startptr, *endptr;
+    const void *startptr, *endptr;
 
     assert(PyUnicode_IS_READY(unicode));
     assert(0 <= start);
@@ -2559,7 +2560,7 @@ as_ucs4(PyObject *string, Py_UCS4 *target, Py_ssize_t targetsize,
         int copy_null)
 {
     int kind;
-    void *data;
+    const void *data;
     Py_ssize_t len, targetlen;
     if (PyUnicode_READY(string) == -1)
         return NULL;
@@ -2586,17 +2587,19 @@ as_ucs4(PyObject *string, Py_UCS4 *target, Py_ssize_t targetsize,
         }
     }
     if (kind == PyUnicode_1BYTE_KIND) {
-        Py_UCS1 *start = (Py_UCS1 *) data;
+        const Py_UCS1 *start = (const Py_UCS1 *) data;
         _PyUnicode_CONVERT_BYTES(Py_UCS1, Py_UCS4, start, start + len, target);
     }
     else if (kind == PyUnicode_2BYTE_KIND) {
-        Py_UCS2 *start = (Py_UCS2 *) data;
+        const Py_UCS2 *start = (const Py_UCS2 *) data;
         _PyUnicode_CONVERT_BYTES(Py_UCS2, Py_UCS4, start, start + len, target);
     }
-    else {
+    else if (kind == PyUnicode_4BYTE_KIND) {
-        assert(kind == PyUnicode_4BYTE_KIND);
         memcpy(target, data, len * sizeof(Py_UCS4));
     }
+    else {
+        Py_UNREACHABLE();
+    }
     if (copy_null)
         target[len] = 0;
     return target;
@@ -4105,7 +4108,7 @@ PyUnicode_GetLength(PyObject *unicode)
 Py_UCS4
 PyUnicode_ReadChar(PyObject *unicode, Py_ssize_t index)
 {
-    void *data;
+    const void *data;
     int kind;
 
     if (!PyUnicode_Check(unicode)) {
@@ -4707,7 +4710,7 @@ _PyUnicode_EncodeUTF7(PyObject *str,
                       const char *errors)
 {
     int kind;
-    void *data;
+    const void *data;
     Py_ssize_t len;
     PyObject *v;
     int inShift = 0;
@@ -4950,7 +4953,7 @@ unicode_decode_utf8(const char *s, Py_ssize_t size,
     if (u == NULL) {
         return NULL;
     }
-    s += ascii_decode(s, end, PyUnicode_DATA(u));
+    s += ascii_decode(s, end, PyUnicode_1BYTE_DATA(u));
     if (s == end) {
         return u;
     }
@@ -5380,7 +5383,7 @@ unicode_encode_utf8(PyObject *unicode, _Py_error_handler error_handler,
                                          PyUnicode_UTF8_LENGTH(unicode));
 
     enum PyUnicode_Kind kind = PyUnicode_KIND(unicode);
-    void *data = PyUnicode_DATA(unicode);
+    const void *data = PyUnicode_DATA(unicode);
     Py_ssize_t size = PyUnicode_GET_LENGTH(unicode);
 
     _PyBytesWriter writer;
@@ -5416,7 +5419,7 @@ unicode_fill_utf8(PyObject *unicode)
     assert(!PyUnicode_IS_ASCII(unicode));
 
     enum PyUnicode_Kind kind = PyUnicode_KIND(unicode);
-    void *data = PyUnicode_DATA(unicode);
+    const void *data = PyUnicode_DATA(unicode);
     Py_ssize_t size = PyUnicode_GET_LENGTH(unicode);
 
     _PyBytesWriter writer;
@@ -6425,7 +6428,7 @@ PyUnicode_AsUnicodeEscapeString(PyObject *unicode)
     PyObject *repr;
     char *p;
     enum PyUnicode_Kind kind;
-    void *data;
+    const void *data;
     Py_ssize_t expandsize;
 
     /* Initial allocation is based on the longest-possible character
@@ -6679,7 +6682,7 @@ PyUnicode_AsRawUnicodeEscapeString(PyObject *unicode)
     char *p;
     Py_ssize_t expandsize, pos;
     int kind;
-    void *data;
+    const void *data;
     Py_ssize_t len;
 
     if (!PyUnicode_Check(unicode)) {
@@ -6885,7 +6888,7 @@ unicode_encode_ucs1(PyObject *unicode,
     /* input state */
     Py_ssize_t pos=0, size;
     int kind;
-    void *data;
+    const void *data;
     /* pointer into the output */
     char *str;
     const char *encoding = (limit == 256) ? "latin-1" : "ascii";
@@ -7113,7 +7116,7 @@ PyUnicode_DecodeASCII(const char *s,
     if (u == NULL) {
         return NULL;
     }
-    Py_ssize_t outpos = ascii_decode(s, e, PyUnicode_DATA(u));
+    Py_ssize_t outpos = ascii_decode(s, e, PyUnicode_1BYTE_DATA(u));
     if (outpos == size) {
         return u;
     }
@@ -7800,7 +7803,7 @@ encode_code_page_errors(UINT code_page, PyObject **outbytes,
         else {
             Py_ssize_t i;
             enum PyUnicode_Kind kind;
-            void *data;
+            const void *data;
 
             if (PyUnicode_READY(rep) == -1) {
                 Py_DECREF(rep);
@@ -7958,7 +7961,7 @@ charmap_decode_string(const char *s,
     PyObject *errorHandler = NULL, *exc = NULL;
     Py_ssize_t maplen;
     enum PyUnicode_Kind mapkind;
-    void *mapdata;
+    const void *mapdata;
     Py_UCS4 x;
     unsigned char ch;
 
@@ -7975,7 +7978,7 @@ charmap_decode_string(const char *s,
         /* fast-path for cp037, cp500 and iso8859_1 encodings. iso8859_1
          * is disabled in encoding aliases, latin1 is preferred because
          * its implementation is faster. */
-        Py_UCS1 *mapdata_ucs1 = (Py_UCS1 *)mapdata;
+        const Py_UCS1 *mapdata_ucs1 = (const Py_UCS1 *)mapdata;
         Py_UCS1 *outdata = (Py_UCS1 *)writer->data;
         Py_UCS4 maxchar = writer->maxchar;
 
@@ -7999,7 +8002,7 @@ charmap_decode_string(const char *s,
     while (s < e) {
         if (mapkind == PyUnicode_2BYTE_KIND && maplen >= 256) {
             enum PyUnicode_Kind outkind = writer->kind;
-            Py_UCS2 *mapdata_ucs2 = (Py_UCS2 *)mapdata;
+            const Py_UCS2 *mapdata_ucs2 = (const Py_UCS2 *)mapdata;
             if (outkind == PyUnicode_1BYTE_KIND) {
                 Py_UCS1 *outdata = (Py_UCS1 *)writer->data;
                 Py_UCS4 maxchar = writer->maxchar;
@@ -8279,7 +8282,7 @@ PyUnicode_BuildEncodingMap(PyObject* string)
     unsigned char *mlevel1, *mlevel2, *mlevel3;
     int count2 = 0, count3 = 0;
     int kind;
-    void *data;
+    const void *data;
     Py_ssize_t length;
     Py_UCS4 ch;
 
@@ -8543,7 +8546,7 @@ charmap_encoding_error(
     Py_ssize_t size, repsize;
     Py_ssize_t newpos;
     enum PyUnicode_Kind kind;
-    void *data;
+    const void *data;
     Py_ssize_t index;
     /* startpos for collecting unencodable chars */
     Py_ssize_t collstartpos = *inpos;
@@ -8693,7 +8696,7 @@ _PyUnicode_EncodeCharmap(PyObject *unicode,
     PyObject *error_handler_obj = NULL;
     PyObject *exc = NULL;
     _Py_error_handler error_handler = _Py_ERROR_UNKNOWN;
-    void *data;
+    const void *data;
     int kind;
 
     if (PyUnicode_READY(unicode) == -1)
@@ -9025,7 +9028,8 @@ unicode_fast_translate(PyObject *input, PyObject *mapping,
 {
     Py_UCS1 ascii_table[128], ch, ch2;
     Py_ssize_t len;
-    Py_UCS1 *in, *end, *out;
+    const Py_UCS1 *in, *end;
+    Py_UCS1 *out;
     int res = 0;
 
     len = PyUnicode_GET_LENGTH(input);
@@ -9074,7 +9078,7 @@ _PyUnicode_TranslateCharmap(PyObject *input,
                             const char *errors)
 {
     /* input object */
-    char *data;
+    const void *data;
     Py_ssize_t size, i;
     int kind;
     /* output buffer */
@@ -9093,7 +9097,7 @@ _PyUnicode_TranslateCharmap(PyObject *input,
 
     if (PyUnicode_READY(input) == -1)
         return NULL;
-    data = (char*)PyUnicode_DATA(input);
+    data = PyUnicode_DATA(input);
     kind = PyUnicode_KIND(input);
     size = PyUnicode_GET_LENGTH(input);
 
@@ -9271,7 +9275,7 @@ PyUnicode_TransformDecimalToASCII(Py_UNICODE *s,
     Py_ssize_t i;
     Py_UCS4 maxchar;
     enum PyUnicode_Kind kind;
-    void *data;
+    const void *data;
 
     maxchar = 127;
     for (i = 0; i < length; i++) {
@@ -9313,7 +9317,7 @@ PyUnicode_EncodeDecimal(Py_UNICODE *s,
     PyObject *unicode;
     Py_ssize_t i;
     enum PyUnicode_Kind kind;
-    void *data;
+    const void *data;
 
     if (output == NULL) {
         PyErr_BadArgument();
@@ -9391,7 +9395,7 @@ any_find_slice(PyObject* s1, PyObject* s2,
                int direction)
 {
     int kind1, kind2;
-    void *buf1, *buf2;
+    const void *buf1, *buf2;
     Py_ssize_t len1, len2, result;
 
     kind1 = PyUnicode_KIND(s1);
@@ -9460,8 +9464,9 @@ any_find_slice(PyObject* s1, PyObject* s2,
         }
     }
 
+    assert((kind2 != kind1) == (buf2 != PyUnicode_DATA(s2)));
     if (kind2 != kind1)
-        PyMem_Free(buf2);
+        PyMem_Free((void *)buf2);
 
     return result;
 }
@@ -9620,7 +9625,7 @@ PyUnicode_Count(PyObject *str,
 {
     Py_ssize_t result;
     int kind1, kind2;
-    void *buf1 = NULL, *buf2 = NULL;
+    const void *buf1 = NULL, *buf2 = NULL;
     Py_ssize_t len1, len2;
 
     if (ensure_unicode(str) < 0 || ensure_unicode(substr) < 0)
@@ -9649,24 +9654,24 @@ PyUnicode_Count(PyObject *str,
     case PyUnicode_1BYTE_KIND:
         if (PyUnicode_IS_ASCII(str) && PyUnicode_IS_ASCII(substr))
             result = asciilib_count(
-                ((Py_UCS1*)buf1) + start, end - start,
+                ((const Py_UCS1*)buf1) + start, end - start,
                 buf2, len2, PY_SSIZE_T_MAX
                 );
         else
             result = ucs1lib_count(
-                ((Py_UCS1*)buf1) + start, end - start,
+                ((const Py_UCS1*)buf1) + start, end - start,
                 buf2, len2, PY_SSIZE_T_MAX
                 );
         break;
     case PyUnicode_2BYTE_KIND:
         result = ucs2lib_count(
-            ((Py_UCS2*)buf1) + start, end - start,
+            ((const Py_UCS2*)buf1) + start, end - start,
             buf2, len2, PY_SSIZE_T_MAX
             );
         break;
     case PyUnicode_4BYTE_KIND:
         result = ucs4lib_count(
-            ((Py_UCS4*)buf1) + start, end - start,
+            ((const Py_UCS4*)buf1) + start, end - start,
             buf2, len2, PY_SSIZE_T_MAX
             );
         break;
@@ -9674,13 +9679,15 @@ PyUnicode_Count(PyObject *str,
         Py_UNREACHABLE();
     }
 
+    assert((kind2 != kind1) == (buf2 != PyUnicode_DATA(substr)));
     if (kind2 != kind1)
-        PyMem_Free(buf2);
+        PyMem_Free((void *)buf2);
 
     return result;
   onError:
-    if (kind2 != kind1 && buf2)
+    assert((kind2 != kind1) == (buf2 != PyUnicode_DATA(substr)));
-        PyMem_Free(buf2);
+    if (kind2 != kind1)
+        PyMem_Free((void *)buf2);
     return -1;
 }
 
@@ -9728,8 +9735,8 @@ tailmatch(PyObject *self,
 {
     int kind_self;
     int kind_sub;
-    void *data_self;
+    const void *data_self;
-    void *data_sub;
+    const void *data_sub;
     Py_ssize_t offset;
     Py_ssize_t i;
     Py_ssize_t end_sub;
@@ -9803,7 +9810,8 @@ static PyObject *
 ascii_upper_or_lower(PyObject *self, int lower)
 {
     Py_ssize_t len = PyUnicode_GET_LENGTH(self);
-    char *resdata, *data = PyUnicode_DATA(self);
+    const char *data = PyUnicode_DATA(self);
+    char *resdata;
     PyObject *res;
 
     res = PyUnicode_New(len, 127);
@@ -9818,7 +9826,7 @@ ascii_upper_or_lower(PyObject *self, int lower)
 }
 
 static Py_UCS4
-handle_capital_sigma(int kind, void *data, Py_ssize_t length, Py_ssize_t i)
+handle_capital_sigma(int kind, const void *data, Py_ssize_t length, Py_ssize_t i)
 {
     Py_ssize_t j;
     int final_sigma;
@@ -9847,7 +9855,7 @@ handle_capital_sigma(int kind, void *data, Py_ssize_t length, Py_ssize_t i)
 }
 
 static int
-lower_ucs4(int kind, void *data, Py_ssize_t length, Py_ssize_t i,
+lower_ucs4(int kind, const void *data, Py_ssize_t length, Py_ssize_t i,
            Py_UCS4 c, Py_UCS4 *mapped)
 {
     /* Obscure special case. */
@@ -9859,7 +9867,7 @@ lower_ucs4(int kind, void *data, Py_ssize_t length, Py_ssize_t i,
 }
 
 static Py_ssize_t
-do_capitalize(int kind, void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *maxchar)
+do_capitalize(int kind, const void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *maxchar)
 {
     Py_ssize_t i, k = 0;
     int n_res, j;
@@ -9883,7 +9891,7 @@ do_capitalize(int kind, void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *ma
 }
 
 static Py_ssize_t
-do_swapcase(int kind, void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *maxchar) {
+do_swapcase(int kind, const void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *maxchar) {
     Py_ssize_t i, k = 0;
 
     for (i = 0; i < length; i++) {
@@ -9908,7 +9916,7 @@ do_swapcase(int kind, void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *maxc
 }
 
 static Py_ssize_t
-do_upper_or_lower(int kind, void *data, Py_ssize_t length, Py_UCS4 *res,
+do_upper_or_lower(int kind, const void *data, Py_ssize_t length, Py_UCS4 *res,
                   Py_UCS4 *maxchar, int lower)
 {
     Py_ssize_t i, k = 0;
@@ -9929,19 +9937,19 @@ do_upper_or_lower(int kind, void *data, Py_ssize_t length, Py_UCS4 *res,
 }
 
 static Py_ssize_t
-do_upper(int kind, void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *maxchar)
+do_upper(int kind, const void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *maxchar)
 {
     return do_upper_or_lower(kind, data, length, res, maxchar, 0);
 }
 
 static Py_ssize_t
-do_lower(int kind, void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *maxchar)
+do_lower(int kind, const void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *maxchar)
 {
     return do_upper_or_lower(kind, data, length, res, maxchar, 1);
 }
 
 static Py_ssize_t
-do_casefold(int kind, void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *maxchar)
+do_casefold(int kind, const void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *maxchar)
 {
     Py_ssize_t i, k = 0;
 
@@ -9958,7 +9966,7 @@ do_casefold(int kind, void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *maxc
 }
 
 static Py_ssize_t
-do_title(int kind, void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *maxchar)
+do_title(int kind, const void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *maxchar)
 {
     Py_ssize_t i, k = 0;
     int previous_is_cased;
@@ -9986,12 +9994,13 @@ do_title(int kind, void *data, Py_ssize_t length, Py_UCS4 *res, Py_UCS4 *maxchar
 
 static PyObject *
 case_operation(PyObject *self,
-               Py_ssize_t (*perform)(int, void *, Py_ssize_t, Py_UCS4 *, Py_UCS4 *))
+               Py_ssize_t (*perform)(int, const void *, Py_ssize_t, Py_UCS4 *, Py_UCS4 *))
 {
     PyObject *res = NULL;
     Py_ssize_t length, newlength = 0;
     int kind, outkind;
-    void *data, *outdata;
+    const void *data;
+    void *outdata;
     Py_UCS4 maxchar = 0, *tmp, *tmpend;
 
     assert(PyUnicode_IS_READY(self));
@@ -10358,7 +10367,7 @@ split(PyObject *self,
       Py_ssize_t maxcount)
 {
     int kind1, kind2;
-    void *buf1, *buf2;
+    const void *buf1, *buf2;
     Py_ssize_t len1, len2;
     PyObject* out;
 
@@ -10438,8 +10447,9 @@ split(PyObject *self,
     default:
         out = NULL;
     }
+    assert((kind2 != kind1) == (buf2 != PyUnicode_DATA(substring)));
     if (kind2 != kind1)
-        PyMem_Free(buf2);
+        PyMem_Free((void *)buf2);
     return out;
 }
 
@@ -10449,7 +10459,7 @@ rsplit(PyObject *self,
        Py_ssize_t maxcount)
 {
     int kind1, kind2;
-    void *buf1, *buf2;
+    const void *buf1, *buf2;
     Py_ssize_t len1, len2;
     PyObject* out;
 
@@ -10529,14 +10539,15 @@ rsplit(PyObject *self,
     default:
         out = NULL;
     }
+    assert((kind2 != kind1) == (buf2 != PyUnicode_DATA(substring)));
     if (kind2 != kind1)
-        PyMem_Free(buf2);
+        PyMem_Free((void *)buf2);
     return out;
 }
 
 static Py_ssize_t
-anylib_find(int kind, PyObject *str1, void *buf1, Py_ssize_t len1,
+anylib_find(int kind, PyObject *str1, const void *buf1, Py_ssize_t len1,
-            PyObject *str2, void *buf2, Py_ssize_t len2, Py_ssize_t offset)
+            PyObject *str2, const void *buf2, Py_ssize_t len2, Py_ssize_t offset)
 {
     switch (kind) {
     case PyUnicode_1BYTE_KIND:
@@ -10553,8 +10564,8 @@ anylib_find(int kind, PyObject *str1, void *buf1, Py_ssize_t len1,
 }
 
 static Py_ssize_t
-anylib_count(int kind, PyObject *sstr, void* sbuf, Py_ssize_t slen,
+anylib_count(int kind, PyObject *sstr, const void* sbuf, Py_ssize_t slen,
-             PyObject *str1, void *buf1, Py_ssize_t len1, Py_ssize_t maxcount)
+             PyObject *str1, const void *buf1, Py_ssize_t len1, Py_ssize_t maxcount)
 {
     switch (kind) {
     case PyUnicode_1BYTE_KIND:
@@ -10600,9 +10611,9 @@ replace(PyObject *self, PyObject *str1,
         PyObject *str2, Py_ssize_t maxcount)
 {
     PyObject *u;
-    char *sbuf = PyUnicode_DATA(self);
+    const char *sbuf = PyUnicode_DATA(self);
-    char *buf1 = PyUnicode_DATA(str1);
+    const void *buf1 = PyUnicode_DATA(str1);
-    char *buf2 = PyUnicode_DATA(str2);
+    const void *buf2 = PyUnicode_DATA(str2);
     int srelease = 0, release1 = 0, release2 = 0;
     int skind = PyUnicode_KIND(self);
     int kind1 = PyUnicode_KIND(str1);
@@ -10680,7 +10691,8 @@ replace(PyObject *self, PyObject *str1,
                 /* widen self and buf1 */
                 rkind = kind2;
                 if (release1) {
-                    PyMem_Free(buf1);
+                    assert(buf1 != PyUnicode_DATA(str1));
+                    PyMem_Free((void *)buf1);
                     buf1 = PyUnicode_DATA(str1);
                     release1 = 0;
                 }
@@ -10745,7 +10757,8 @@ replace(PyObject *self, PyObject *str1,
             if (!sbuf) goto error;
             srelease = 1;
             if (release1) {
-                PyMem_Free(buf1);
+                assert(buf1 != PyUnicode_DATA(str1));
+                PyMem_Free((void *)buf1);
                 buf1 = PyUnicode_DATA(str1);
                 release1 = 0;
             }
@@ -10837,32 +10850,41 @@ replace(PyObject *self, PyObject *str1,
     }
 
   done:
+    assert(srelease == (sbuf != PyUnicode_DATA(self)));
+    assert(release1 == (buf1 != PyUnicode_DATA(str1)));
+    assert(release2 == (buf2 != PyUnicode_DATA(str2)));
     if (srelease)
-        PyMem_FREE(sbuf);
+        PyMem_FREE((void *)sbuf);
     if (release1)
-        PyMem_FREE(buf1);
+        PyMem_FREE((void *)buf1);
     if (release2)
-        PyMem_FREE(buf2);
+        PyMem_FREE((void *)buf2);
     assert(_PyUnicode_CheckConsistency(u, 1));
     return u;
 
   nothing:
     /* nothing to replace; return original string (when possible) */
+    assert(srelease == (sbuf != PyUnicode_DATA(self)));
+    assert(release1 == (buf1 != PyUnicode_DATA(str1)));
+    assert(release2 == (buf2 != PyUnicode_DATA(str2)));
     if (srelease)
-        PyMem_FREE(sbuf);
+        PyMem_FREE((void *)sbuf);
     if (release1)
-        PyMem_FREE(buf1);
+        PyMem_FREE((void *)buf1);
     if (release2)
-        PyMem_FREE(buf2);
+        PyMem_FREE((void *)buf2);
     return unicode_result_unchanged(self);
 
   error:
-    if (srelease && sbuf)
+    assert(srelease == (sbuf != PyUnicode_DATA(self)));
-        PyMem_FREE(sbuf);
+    assert(release1 == (buf1 != PyUnicode_DATA(str1)));
-    if (release1 && buf1)
+    assert(release2 == (buf2 != PyUnicode_DATA(str2)));
-        PyMem_FREE(buf1);
+    if (srelease)
-    if (release2 && buf2)
+        PyMem_FREE((void *)sbuf);
-        PyMem_FREE(buf2);
+    if (release1)
+        PyMem_FREE((void *)buf1);
+    if (release2)
+        PyMem_FREE((void *)buf2);
     return NULL;
 }
 
@@ -10999,7 +11021,7 @@ unicode_compare(PyObject *str1, PyObject *str2)
     while (0)
 
     int kind1, kind2;
-    void *data1, *data2;
+    const void *data1, *data2;
     Py_ssize_t len1, len2, len;
 
     kind1 = PyUnicode_KIND(str1);
@@ -11100,7 +11122,7 @@ static int
 unicode_compare_eq(PyObject *str1, PyObject *str2)
 {
     int kind;
-    void *data1, *data2;
+    const void *data1, *data2;
     Py_ssize_t len;
     int cmp;
 
@@ -11185,7 +11207,7 @@ PyUnicode_CompareWithASCIIString(PyObject* uni, const char* str)
         return 0;
     }
     else {
-        void *data = PyUnicode_DATA(uni);
+        const void *data = PyUnicode_DATA(uni);
         /* Compare Unicode string and source character set string */
         for (i = 0; (chr = PyUnicode_READ(kind, data, i)) && str[i]; i++)
             if (chr != (unsigned char)str[i])
@@ -11334,7 +11356,7 @@ int
 PyUnicode_Contains(PyObject *str, PyObject *substr)
 {
     int kind1, kind2;
-    void *buf1, *buf2;
+    const void *buf1, *buf2;
     Py_ssize_t len1, len2;
     int result;
 
@@ -11384,8 +11406,9 @@ PyUnicode_Contains(PyObject *str, PyObject *substr)
         Py_UNREACHABLE();
     }
 
+    assert((kind2 == kind1) == (buf2 == PyUnicode_DATA(substr)));
     if (kind2 != kind1)
-        PyMem_Free(buf2);
+        PyMem_Free((void *)buf2);
 
     return result;
 }
@@ -11562,7 +11585,7 @@ unicode_count(PyObject *self, PyObject *args)
     Py_ssize_t end = PY_SSIZE_T_MAX;
     PyObject *result;
     int kind1, kind2;
-    void *buf1, *buf2;
+    const void *buf1, *buf2;
     Py_ssize_t len1, len2, iresult;
 
     if (!parse_args_finds_unicode("count", args, &substring, &start, &end))
@@ -11589,19 +11612,19 @@ unicode_count(PyObject *self, PyObject *args)
     switch (kind1) {
     case PyUnicode_1BYTE_KIND:
         iresult = ucs1lib_count(
-            ((Py_UCS1*)buf1) + start, end - start,
+            ((const Py_UCS1*)buf1) + start, end - start,
             buf2, len2, PY_SSIZE_T_MAX
             );
         break;
     case PyUnicode_2BYTE_KIND:
         iresult = ucs2lib_count(
-            ((Py_UCS2*)buf1) + start, end - start,
+            ((const Py_UCS2*)buf1) + start, end - start,
             buf2, len2, PY_SSIZE_T_MAX
             );
         break;
     case PyUnicode_4BYTE_KIND:
         iresult = ucs4lib_count(
-            ((Py_UCS4*)buf1) + start, end - start,
+            ((const Py_UCS4*)buf1) + start, end - start,
             buf2, len2, PY_SSIZE_T_MAX
             );
         break;
@@ -11611,8 +11634,9 @@ unicode_count(PyObject *self, PyObject *args)
 
     result = PyLong_FromSsize_t(iresult);
 
+    assert((kind2 == kind1) == (buf2 == PyUnicode_DATA(substring)));
     if (kind2 != kind1)
-        PyMem_Free(buf2);
+        PyMem_Free((void *)buf2);
 
     return result;
 }
@@ -11656,7 +11680,8 @@ unicode_expandtabs_impl(PyObject *self, int tabsize)
     Py_ssize_t i, j, line_pos, src_len, incr;
     Py_UCS4 ch;
     PyObject *u;
-    void *src_data, *dest_data;
+    const void *src_data;
+    void *dest_data;
     int kind;
     int found;
 
@@ -11762,7 +11787,7 @@ unicode_find(PyObject *self, PyObject *args)
 static PyObject *
 unicode_getitem(PyObject *self, Py_ssize_t index)
 {
-    void *data;
+    const void *data;
     enum PyUnicode_Kind kind;
     Py_UCS4 ch;
 
@@ -11875,7 +11900,7 @@ unicode_islower_impl(PyObject *self)
 {
     Py_ssize_t i, length;
     int kind;
-    void *data;
+    const void *data;
     int cased;
 
     if (PyUnicode_READY(self) == -1)
@@ -11920,7 +11945,7 @@ unicode_isupper_impl(PyObject *self)
 {
     Py_ssize_t i, length;
     int kind;
-    void *data;
+    const void *data;
     int cased;
 
     if (PyUnicode_READY(self) == -1)
@@ -11965,7 +11990,7 @@ unicode_istitle_impl(PyObject *self)
 {
     Py_ssize_t i, length;
     int kind;
-    void *data;
+    const void *data;
     int cased, previous_is_cased;
 
     if (PyUnicode_READY(self) == -1)
@@ -12023,7 +12048,7 @@ unicode_isspace_impl(PyObject *self)
 {
     Py_ssize_t i, length;
     int kind;
-    void *data;
+    const void *data;
 
     if (PyUnicode_READY(self) == -1)
         return NULL;
@@ -12063,7 +12088,7 @@ unicode_isalpha_impl(PyObject *self)
 {
     Py_ssize_t i, length;
     int kind;
-    void *data;
+    const void *data;
 
     if (PyUnicode_READY(self) == -1)
         return NULL;
@@ -12101,7 +12126,7 @@ unicode_isalnum_impl(PyObject *self)
 /*[clinic end generated code: output=a5a23490ffc3660c input=5c6579bf2e04758c]*/
 {
     int kind;
-    void *data;
+    const void *data;
     Py_ssize_t len, i;
 
     if (PyUnicode_READY(self) == -1)
@@ -12144,7 +12169,7 @@ unicode_isdecimal_impl(PyObject *self)
 {
     Py_ssize_t i, length;
     int kind;
-    void *data;
+    const void *data;
 
     if (PyUnicode_READY(self) == -1)
         return NULL;
@@ -12183,7 +12208,7 @@ unicode_isdigit_impl(PyObject *self)
 {
     Py_ssize_t i, length;
     int kind;
-    void *data;
+    const void *data;
 
     if (PyUnicode_READY(self) == -1)
         return NULL;
@@ -12223,7 +12248,7 @@ unicode_isnumeric_impl(PyObject *self)
 {
     Py_ssize_t i, length;
     int kind;
-    void *data;
+    const void *data;
 
     if (PyUnicode_READY(self) == -1)
         return NULL;
@@ -12260,7 +12285,7 @@ PyUnicode_IsIdentifier(PyObject *self)
     }
 
     int kind = 0;
-    void *data = NULL;
+    const void *data = NULL;
     const wchar_t *wstr = NULL;
     Py_UCS4 ch;
     if (ready) {
@@ -12329,7 +12354,7 @@ unicode_isprintable_impl(PyObject *self)
 {
     Py_ssize_t i, length;
     int kind;
-    void *data;
+    const void *data;
 
     if (PyUnicode_READY(self) == -1)
         return NULL;
@@ -12434,7 +12459,7 @@ static const char *stripfuncnames[] = {"lstrip", "rstrip", "strip"};
 PyObject *
 _PyUnicode_XStrip(PyObject *self, int striptype, PyObject *sepobj)
 {
-    void *data;
+    const void *data;
     int kind;
     Py_ssize_t i, j, len;
     BLOOM_MASK sepmask;
@@ -12484,7 +12509,7 @@ _PyUnicode_XStrip(PyObject *self, int striptype, PyObject *sepobj)
 PyObject*
 PyUnicode_Substring(PyObject *self, Py_ssize_t start, Py_ssize_t end)
 {
-    unsigned char *data;
+    const unsigned char *data;
     int kind;
     Py_ssize_t length;
 
@@ -12507,7 +12532,7 @@ PyUnicode_Substring(PyObject *self, Py_ssize_t start, Py_ssize_t end)
     length = end - start;
     if (PyUnicode_IS_ASCII(self)) {
         data = PyUnicode_1BYTE_DATA(self);
-        return _PyUnicode_FromASCII((char*)(data + start), length);
+        return _PyUnicode_FromASCII((const char*)(data + start), length);
     }
     else {
         kind = PyUnicode_KIND(self);
@@ -12529,7 +12554,7 @@ do_strip(PyObject *self, int striptype)
     len = PyUnicode_GET_LENGTH(self);
 
     if (PyUnicode_IS_ASCII(self)) {
-        Py_UCS1 *data = PyUnicode_1BYTE_DATA(self);
+        const Py_UCS1 *data = PyUnicode_1BYTE_DATA(self);
 
         i = 0;
         if (striptype != RIGHTSTRIP) {
@@ -12555,7 +12580,7 @@ do_strip(PyObject *self, int striptype)
     }
     else {
         int kind = PyUnicode_KIND(self);
-        void *data = PyUnicode_DATA(self);
+        const void *data = PyUnicode_DATA(self);
 
         i = 0;
         if (striptype != RIGHTSTRIP) {
@@ -12688,8 +12713,8 @@ unicode_repeat(PyObject *str, Py_ssize_t len)
     assert(PyUnicode_KIND(u) == PyUnicode_KIND(str));
 
     if (PyUnicode_GET_LENGTH(str) == 1) {
-        const int kind = PyUnicode_KIND(str);
+        int kind = PyUnicode_KIND(str);
-        const Py_UCS4 fill_char = PyUnicode_READ(kind, PyUnicode_DATA(str), 0);
+        Py_UCS4 fill_char = PyUnicode_READ(kind, PyUnicode_DATA(str), 0);
         if (kind == PyUnicode_1BYTE_KIND) {
             void *to = PyUnicode_DATA(u);
             memset(to, (unsigned char)fill_char, len);
@@ -12708,7 +12733,7 @@ unicode_repeat(PyObject *str, Py_ssize_t len)
     else {
         /* number of characters copied this far */
         Py_ssize_t done = PyUnicode_GET_LENGTH(str);
-        const Py_ssize_t char_size = PyUnicode_KIND(str);
+        Py_ssize_t char_size = PyUnicode_KIND(str);
         char *to = (char *) PyUnicode_DATA(u);
         memcpy(to, PyUnicode_DATA(str),
                   PyUnicode_GET_LENGTH(str) * char_size);
@@ -12769,7 +12794,8 @@ unicode_repr(PyObject *unicode)
     Py_ssize_t osize, squote, dquote, i, o;
     Py_UCS4 max, quote;
     int ikind, okind, unchanged;
-    void *idata, *odata;
+    const void *idata;
+    void *odata;
 
     if (PyUnicode_READY(unicode) == -1)
         return NULL;
@@ -13062,7 +13088,7 @@ PyUnicode_Partition(PyObject *str_obj, PyObject *sep_obj)
 {
     PyObject* out;
     int kind1, kind2;
-    void *buf1, *buf2;
+    const void *buf1, *buf2;
     Py_ssize_t len1, len2;
 
     if (ensure_unicode(str_obj) < 0 || ensure_unicode(sep_obj) < 0)
@@ -13107,8 +13133,9 @@ PyUnicode_Partition(PyObject *str_obj, PyObject *sep_obj)
         Py_UNREACHABLE();
     }
 
+    assert((kind2 == kind1) == (buf2 == PyUnicode_DATA(sep_obj)));
     if (kind2 != kind1)
-        PyMem_Free(buf2);
+        PyMem_Free((void *)buf2);
 
     return out;
 }
@@ -13119,7 +13146,7 @@ PyUnicode_RPartition(PyObject *str_obj, PyObject *sep_obj)
 {
     PyObject* out;
     int kind1, kind2;
-    void *buf1, *buf2;
+    const void *buf1, *buf2;
     Py_ssize_t len1, len2;
 
     if (ensure_unicode(str_obj) < 0 || ensure_unicode(sep_obj) < 0)
@@ -13164,8 +13191,9 @@ PyUnicode_RPartition(PyObject *str_obj, PyObject *sep_obj)
         Py_UNREACHABLE();
     }
 
+    assert((kind2 == kind1) == (buf2 == PyUnicode_DATA(sep_obj)));
     if (kind2 != kind1)
-        PyMem_Free(buf2);
+        PyMem_Free((void *)buf2);
 
     return out;
 }
@@ -13321,7 +13349,7 @@ unicode_maketrans_impl(PyObject *x, PyObject *y, PyObject *z)
         return NULL;
     if (y != NULL) {
         int x_kind, y_kind, z_kind;
-        void *x_data, *y_data, *z_data;
+        const void *x_data, *y_data, *z_data;
 
         /* x must be a string too, of equal length */
         if (!PyUnicode_Check(x)) {
@@ -13370,7 +13398,7 @@ unicode_maketrans_impl(PyObject *x, PyObject *y, PyObject *z)
         }
     } else {
         int kind;
-        void *data;
+        const void *data;
 
         /* x must be a dict */
         if (!PyDict_CheckExact(x)) {
@@ -13471,7 +13499,7 @@ unicode_zfill_impl(PyObject *self, Py_ssize_t width)
     Py_ssize_t fill;
     PyObject *u;
     int kind;
-    void *data;
+    const void *data;
     Py_UCS4 chr;
 
     if (PyUnicode_READY(self) == -1)
@@ -14144,7 +14172,8 @@ unicode_subscript(PyObject* self, PyObject* item)
         Py_ssize_t start, stop, step, slicelength, i;
         size_t cur;
         PyObject *result;
-        void *src_data, *dest_data;
+        const void *src_data;
+        void *dest_data;
         int src_kind, dest_kind;
         Py_UCS4 ch, max_char, kind_limit;
 
@@ -14215,7 +14244,7 @@ struct unicode_formatter_t {
 
     enum PyUnicode_Kind fmtkind;
     Py_ssize_t fmtcnt, fmtpos;
-    void *fmtdata;
+    const void *fmtdata;
     PyObject *fmtstr;
 
     _PyUnicodeWriter writer;
@@ -14889,7 +14918,7 @@ unicode_format_arg_output(struct unicode_formatter_t *ctx,
 {
     Py_ssize_t len;
     enum PyUnicode_Kind kind;
-    void *pbuf;
+    const void *pbuf;
     Py_ssize_t pindex;
     Py_UCS4 signchar;
     Py_ssize_t buflen;
@@ -15556,7 +15585,7 @@ unicodeiter_next(unicodeiterobject *it)
 
     if (it->it_index < PyUnicode_GET_LENGTH(seq)) {
         int kind = PyUnicode_KIND(seq);
-        void *data = PyUnicode_DATA(seq);
+        const void *data = PyUnicode_DATA(seq);
         Py_UCS4 chr = PyUnicode_READ(kind, data, it->it_index);
         item = PyUnicode_FromOrdinal(chr);
         if (item != NULL)

Python/_warnings.c

@@ -435,7 +435,7 @@ normalize_module(PyObject *filename)
 {
     PyObject *module;
     int kind;
-    void *data;
+    const void *data;
     Py_ssize_t len;
 
     len = PyUnicode_GetLength(filename);
@@ -519,7 +519,7 @@ show_warning(PyObject *filename, int lineno, PyObject *text,
     /* Print "  source_line\n" */
     if (sourceline) {
         int kind;
-        void *data;
+        const void *data;
         Py_ssize_t i, len;
         Py_UCS4 ch;
         PyObject *truncated;

Python/ast.c

@@ -4588,7 +4588,7 @@ decode_unicode_with_escapes(struct compiling *c, const node *n, const char *s,
         if (*s & 0x80) { /* XXX inefficient */
             PyObject *w;
             int kind;
-            void *data;
+            const void *data;
             Py_ssize_t len, i;
             w = decode_utf8(c, &s, end);
             if (w == NULL) {

Python/codecs.c

@@ -701,8 +701,7 @@ PyObject *PyCodec_ReplaceErrors(PyObject *exc)
 
     if (PyObject_TypeCheck(exc, (PyTypeObject *)PyExc_UnicodeEncodeError)) {
         PyObject *res;
-        int kind;
+        Py_UCS1 *outp;
-        void *data;
         if (PyUnicodeEncodeError_GetStart(exc, &start))
             return NULL;
         if (PyUnicodeEncodeError_GetEnd(exc, &end))
@@ -711,10 +710,10 @@ PyObject *PyCodec_ReplaceErrors(PyObject *exc)
         res = PyUnicode_New(len, '?');
         if (res == NULL)
             return NULL;
-        kind = PyUnicode_KIND(res);
+        assert(PyUnicode_KIND(res) == PyUnicode_1BYTE_KIND);
-        data = PyUnicode_DATA(res);
+        outp = PyUnicode_1BYTE_DATA(res);
         for (i = 0; i < len; ++i)
-            PyUnicode_WRITE(kind, data, i, '?');
+            outp[i] = '?';
         assert(_PyUnicode_CheckConsistency(res, 1));
         return Py_BuildValue("(Nn)", res, end);
     }
@@ -727,8 +726,7 @@ PyObject *PyCodec_ReplaceErrors(PyObject *exc)
     }
     else if (PyObject_TypeCheck(exc, (PyTypeObject *)PyExc_UnicodeTranslateError)) {
         PyObject *res;
-        int kind;
+        Py_UCS2 *outp;
-        void *data;
         if (PyUnicodeTranslateError_GetStart(exc, &start))
             return NULL;
         if (PyUnicodeTranslateError_GetEnd(exc, &end))
@@ -737,10 +735,10 @@ PyObject *PyCodec_ReplaceErrors(PyObject *exc)
         res = PyUnicode_New(len, Py_UNICODE_REPLACEMENT_CHARACTER);
         if (res == NULL)
             return NULL;
-        kind = PyUnicode_KIND(res);
+        assert(PyUnicode_KIND(res) == PyUnicode_2BYTE_KIND);
-        data = PyUnicode_DATA(res);
+        outp = PyUnicode_2BYTE_DATA(res);
         for (i = 0; i < len; i++)
-            PyUnicode_WRITE(kind, data, i, Py_UNICODE_REPLACEMENT_CHARACTER);
+            outp[i] = Py_UNICODE_REPLACEMENT_CHARACTER;
         assert(_PyUnicode_CheckConsistency(res, 1));
         return Py_BuildValue("(Nn)", res, end);
     }
@@ -759,7 +757,7 @@ PyObject *PyCodec_XMLCharRefReplaceErrors(PyObject *exc)
         Py_ssize_t start;
         Py_ssize_t end;
         PyObject *res;
-        unsigned char *outp;
+        Py_UCS1 *outp;
         Py_ssize_t ressize;
         Py_UCS4 ch;
         if (PyUnicodeEncodeError_GetStart(exc, &start))
@@ -855,7 +853,7 @@ PyObject *PyCodec_BackslashReplaceErrors(PyObject *exc)
     Py_ssize_t start;
     Py_ssize_t end;
     PyObject *res;
-    unsigned char *outp;
+    Py_UCS1 *outp;
     int ressize;
     Py_UCS4 c;
 
@@ -966,7 +964,7 @@ PyObject *PyCodec_NameReplaceErrors(PyObject *exc)
         Py_ssize_t start;
         Py_ssize_t end;
         PyObject *res;
-        unsigned char *outp;
+        Py_UCS1 *outp;
         Py_ssize_t ressize;
         int replsize;
         Py_UCS4 c;

Python/formatter_unicode.c

@@ -62,7 +62,7 @@ get_integer(PyObject *str, Py_ssize_t *ppos, Py_ssize_t end,
     Py_ssize_t accumulator, digitval, pos = *ppos;
     int numdigits;
     int kind = PyUnicode_KIND(str);
-    void *data = PyUnicode_DATA(str);
+    const void *data = PyUnicode_DATA(str);
 
     accumulator = numdigits = 0;
     for (; pos < end; pos++, numdigits++) {
@@ -170,7 +170,7 @@ parse_internal_render_format_spec(PyObject *format_spec,
 {
     Py_ssize_t pos = start;
     int kind = PyUnicode_KIND(format_spec);
-    void *data = PyUnicode_DATA(format_spec);
+    const void *data = PyUnicode_DATA(format_spec);
     /* end-pos is used throughout this code to specify the length of
        the input string */
 #define READ_spec(index) PyUnicode_READ(kind, data, index)
@@ -443,7 +443,7 @@ parse_number(PyObject *s, Py_ssize_t pos, Py_ssize_t end,
 {
     Py_ssize_t remainder;
     int kind = PyUnicode_KIND(s);
-    void *data = PyUnicode_DATA(s);
+    const void *data = PyUnicode_DATA(s);
 
     while (pos<end && Py_ISDIGIT(PyUnicode_READ(kind, data, pos)))
         ++pos;

Python/getargs.c

@@ -923,7 +923,7 @@ convertsimple(PyObject *arg, const char **p_format, va_list *p_va, int flags,
     case 'C': {/* unicode char */
         int *p = va_arg(*p_va, int *);
         int kind;
-        void *data;
+        const void *data;
 
         if (!PyUnicode_Check(arg))
             return converterr("a unicode character", arg, msgbuf, bufsize);

Python/traceback.c

@@ -376,7 +376,7 @@ _Py_DisplaySourceLine(PyObject *f, PyObject *filename, int lineno, int indent)
     int fd;
     int i;
     char *found_encoding;
-    char *encoding;
+    const char *encoding;
     PyObject *io;
     PyObject *binary;
     PyObject *fob = NULL;
@@ -384,7 +384,7 @@ _Py_DisplaySourceLine(PyObject *f, PyObject *filename, int lineno, int indent)
     PyObject *res;
     char buf[MAXPATHLEN+1];
     int kind;
-    void *data;
+    const void *data;
 
     /* open the file */
     if (filename == NULL)