gh-155742: Get PyBytes_AS_STRING() as const char* (#155751)

Use "const char*" type instead of "char*" to store
PyBytes_AS_STRING(): treat bytes objects as immutable.

Author: vstinner

Include/internal/pycore_code.h

@@ -205,7 +205,7 @@ _PyLocals_GetKind(PyObject *kinds, int i)
 {
     assert(PyBytes_Check(kinds));
     assert(0 <= i && i < PyBytes_GET_SIZE(kinds));
-    char *ptr = PyBytes_AS_STRING(kinds);
+    const char *ptr = PyBytes_AS_STRING(kinds);
     return (_PyLocals_Kind)(ptr[i]);
 }
 

Modules/_sqlite/blob.c

@@ -472,7 +472,7 @@ subscript_slice(pysqlite_Blob *self, PyObject *item)
         return NULL;
     }
     char *res_buf = PyBytesWriter_GetData(writer);
-    char *blob_buf = PyBytes_AS_STRING(blob);
+    const char *blob_buf = PyBytes_AS_STRING(blob);
 
     size_t cur;
     Py_ssize_t i;

Modules/socketmodule.c

@@ -1811,7 +1811,7 @@ makesockaddr(SOCKET_T sockfd, struct sockaddr *addr, size_t addrlen, int proto)
    (in particular, numeric IP addresses). */
 struct maybe_idna {
     PyObject *obj;
-    char *buf;
+    const char *buf;
 };
 
 static void

Objects/stringlib/codecs.h

@@ -406,7 +406,7 @@ STRINGLIB(utf8_encoder)(PyObject *unicode,
                     writer->overallocate = (newpos < size);
                 }
 
-                char *rep_str;
+                const char *rep_str;
                 Py_ssize_t rep_len;
                 if (PyBytes_Check(rep)) {
                     rep_str = PyBytes_AS_STRING(rep);

Objects/unicodeobject.c

@@ -7314,7 +7314,7 @@ unicode_encode_ucs1(PyObject *unicode,
                     writer->overallocate = (newpos < size);
                 }
 
-                char *rep_str;
+                const char *rep_str;
                 Py_ssize_t rep_len;
                 if (PyBytes_Check(rep)) {
                     /* Directly copy bytes result to output. */

Parser/action_helpers.c

@@ -1481,7 +1481,7 @@ expr_ty _PyPegen_decoded_constant_from_token(Parser* p, Token* tok) {
 }
 
 expr_ty _PyPegen_constant_from_token(Parser* p, Token* tok) {
-    char* bstr = PyBytes_AsString(tok->bytes);
+    const char* bstr = PyBytes_AsString(tok->bytes);
     if (bstr == NULL) {
         return NULL;
     }
@@ -1499,7 +1499,7 @@ expr_ty _PyPegen_constant_from_token(Parser* p, Token* tok) {
 }
 
 expr_ty _PyPegen_constant_from_string(Parser* p, Token* tok) {
-    char* the_str = PyBytes_AsString(tok->bytes);
+    const char* the_str = PyBytes_AsString(tok->bytes);
     if (the_str == NULL) {
         return NULL;
     }

Parser/string_parser.c

@@ -70,7 +70,7 @@ warn_invalid_escape_sequence(Parser *p, const char* buffer, const char *first_in
     char first_quote = 0;
     if (lineno == t->lineno) {
         int quote_count = 0;
-        char* tok = PyBytes_AsString(t->bytes);
+        const char* tok = PyBytes_AsString(t->bytes);
         for (int i = 0; i < PyBytes_Size(t->bytes); i++) {
             if (tok[i] == '\'' || tok[i] == '\"') {
                 if (quote_count == 0) {