diff --git a/Doc/c-api/init.rst b/Doc/c-api/init.rst
index a3113a390fd..4ee61e8a1cf 100644
--- a/Doc/c-api/init.rst
+++ b/Doc/c-api/init.rst
@@ -338,7 +338,7 @@ Process-wide parameters
    .. versionadded:: 3.4
 
 
-.. c:function:: void Py_SetProgramName(wchar_t *name)
+.. c:function:: void Py_SetProgramName(const wchar_t *name)
 
    .. index::
       single: Py_Initialize()
@@ -605,7 +605,7 @@ Process-wide parameters
    .. versionchanged:: 3.4 The *updatepath* value depends on :option:`-I`.
 
 
-.. c:function:: void Py_SetPythonHome(wchar_t *home)
+.. c:function:: void Py_SetPythonHome(const wchar_t *home)
 
    Set the default "home" directory, that is, the location of the standard
    Python libraries.  See :envvar:`PYTHONHOME` for the meaning of the
diff --git a/Include/pylifecycle.h b/Include/pylifecycle.h
index bda51f84c3c..542306004d2 100644
--- a/Include/pylifecycle.h
+++ b/Include/pylifecycle.h
@@ -37,10 +37,10 @@ typedef struct {
 #endif
 
 
-PyAPI_FUNC(void) Py_SetProgramName(wchar_t *);
+PyAPI_FUNC(void) Py_SetProgramName(const wchar_t *);
 PyAPI_FUNC(wchar_t *) Py_GetProgramName(void);
 
-PyAPI_FUNC(void) Py_SetPythonHome(wchar_t *);
+PyAPI_FUNC(void) Py_SetPythonHome(const wchar_t *);
 PyAPI_FUNC(wchar_t *) Py_GetPythonHome(void);
 
 #ifndef Py_LIMITED_API
diff --git a/Misc/NEWS.d/next/C API/2017-12-07-15-58-15.bpo-32241.LbyQt6.rst b/Misc/NEWS.d/next/C API/2017-12-07-15-58-15.bpo-32241.LbyQt6.rst
new file mode 100644
index 00000000000..71fa8baa807
--- /dev/null
+++ b/Misc/NEWS.d/next/C API/2017-12-07-15-58-15.bpo-32241.LbyQt6.rst	
@@ -0,0 +1,2 @@
+:c:func:`Py_SetProgramName` and :c:func:`Py_SetPythonHome` now take the
+``const wchar *`` arguments instead of ``wchar *``.
diff --git a/Modules/getaddrinfo.c b/Modules/getaddrinfo.c
index 06e87bfc8ce..5aaa6e7c814 100644
--- a/Modules/getaddrinfo.c
+++ b/Modules/getaddrinfo.c
@@ -251,7 +251,7 @@ getaddrinfo(const char*hostname, const char*servname,
     if (firsttime) {
         /* translator hack */
         {
-            char *q = getenv("GAI");
+            const char *q = getenv("GAI");
             if (q && inet_pton(AF_INET6, q, &faith_prefix) == 1)
                 translate = YES;
         }
diff --git a/Modules/getpath.c b/Modules/getpath.c
index fc2b5442ce2..11babf0a00b 100644
--- a/Modules/getpath.c
+++ b/Modules/getpath.c
@@ -910,7 +910,7 @@ calculate_init(PyCalculatePath *calculate,
                const _PyMainInterpreterConfig *main_config)
 {
     size_t len;
-    char *path = getenv("PATH");
+    const char *path = getenv("PATH");
     if (path) {
         calculate->path_env = Py_DecodeLocale(path, &len);
         if (!calculate->path_env) {
diff --git a/Modules/main.c b/Modules/main.c
index e536492379d..68ee616da62 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -154,10 +154,10 @@ pymain_usage(int error, const wchar_t* program)
 }
 
 
-static char*
+static const char*
 pymain_get_env_var(const char *name)
 {
-    char *var = Py_GETENV(name);
+    const char *var = Py_GETENV(name);
     if (var && var[0] != '\0') {
         return var;
     }
@@ -170,7 +170,7 @@ pymain_get_env_var(const char *name)
 static void
 pymain_run_startup(PyCompilerFlags *cf)
 {
-    char *startup = pymain_get_env_var("PYTHONSTARTUP");
+    const char *startup = pymain_get_env_var("PYTHONSTARTUP");
     if (startup == NULL) {
         return;
     }
@@ -542,7 +542,7 @@ error:
 
 
 static wchar_t*
-pymain_wstrdup(_PyMain *pymain, wchar_t *str)
+pymain_wstrdup(_PyMain *pymain, const wchar_t *str)
 {
     wchar_t *str2 = _PyMem_RawWcsdup(str);
     if (str2 == NULL) {
@@ -554,7 +554,7 @@ pymain_wstrdup(_PyMain *pymain, wchar_t *str)
 
 
 static int
-pymain_optlist_append(_PyMain *pymain, _Py_OptList *list, wchar_t *str)
+pymain_optlist_append(_PyMain *pymain, _Py_OptList *list, const wchar_t *str)
 {
     wchar_t *str2 = pymain_wstrdup(pymain, str);
     if (str2 == NULL) {
@@ -802,7 +802,7 @@ pymain_warnings_envvar(_PyMain *pymain)
     }
 
 #ifdef MS_WINDOWS
-    wchar_t *wp;
+    const wchar_t *wp;
 
     if ((wp = _wgetenv(L"PYTHONWARNINGS")) && *wp != L'\0') {
         wchar_t *warning, *context = NULL;
@@ -824,7 +824,7 @@ pymain_warnings_envvar(_PyMain *pymain)
         PyMem_RawFree(buf);
     }
 #else
-    char *p = pymain_get_env_var("PYTHONWARNINGS");
+    const char *p = pymain_get_env_var("PYTHONWARNINGS");
     if (p != NULL) {
         char *buf, *oldloc;
 
@@ -909,7 +909,7 @@ config_get_program_name(_PyMainInterpreterConfig *config)
     assert(config->program_name == NULL);
 
     /* If Py_SetProgramName() was called, use its value */
-    wchar_t *program_name = _Py_path_config.program_name;
+    const wchar_t *program_name = _Py_path_config.program_name;
     if (program_name != NULL) {
         config->program_name = _PyMem_RawWcsdup(program_name);
         if (config->program_name == NULL) {
@@ -927,7 +927,7 @@ config_get_program_name(_PyMainInterpreterConfig *config)
        so the actual executable path is passed in an environment variable.
        See Lib/plat-mac/bundlebuiler.py for details about the bootstrap
        script. */
-    char *p = pymain_get_env_var("PYTHONEXECUTABLE");
+    const char *p = pymain_get_env_var("PYTHONEXECUTABLE");
     if (p != NULL) {
         size_t len;
         wchar_t* program_name = Py_DecodeLocale(p, &len);
@@ -939,7 +939,7 @@ config_get_program_name(_PyMainInterpreterConfig *config)
     }
 #ifdef WITH_NEXT_FRAMEWORK
     else {
-        char* pyvenv_launcher = getenv("__PYVENV_LAUNCHER__");
+        const char* pyvenv_launcher = getenv("__PYVENV_LAUNCHER__");
         if (pyvenv_launcher && *pyvenv_launcher) {
             /* Used by Mac/Tools/pythonw.c to forward
              * the argv0 of the stub executable
@@ -1289,7 +1289,7 @@ pymain_parse_cmdline(_PyMain *pymain)
 }
 
 
-static wchar_t*
+static const wchar_t*
 pymain_get_xoption(_PyMain *pymain, wchar_t *name)
 {
     _Py_OptList *list = &pymain->cmdline.xoptions;
@@ -1312,11 +1312,11 @@ pymain_get_xoption(_PyMain *pymain, wchar_t *name)
 
 
 static int
-pymain_str_to_int(char *str, int *result)
+pymain_str_to_int(const char *str, int *result)
 {
     errno = 0;
-    char *endptr = str;
-    long value = strtol(str, &endptr, 10);
+    const char *endptr = str;
+    long value = strtol(str, (char **)&endptr, 10);
     if (*endptr != '\0' || errno == ERANGE) {
         return -1;
     }
@@ -1330,11 +1330,11 @@ pymain_str_to_int(char *str, int *result)
 
 
 static int
-pymain_wstr_to_int(wchar_t *wstr, int *result)
+pymain_wstr_to_int(const wchar_t *wstr, int *result)
 {
     errno = 0;
-    wchar_t *endptr = wstr;
-    long value = wcstol(wstr, &endptr, 10);
+    const wchar_t *endptr = wstr;
+    long value = wcstol(wstr, (wchar_t **)&endptr, 10);
     if (*endptr != '\0' || errno == ERANGE) {
         return -1;
     }
@@ -1353,7 +1353,7 @@ pymain_init_tracemalloc(_PyMain *pymain)
     int nframe;
     int valid;
 
-    char *env = pymain_get_env_var("PYTHONTRACEMALLOC");
+    const char *env = pymain_get_env_var("PYTHONTRACEMALLOC");
     if (env) {
         if (!pymain_str_to_int(env, &nframe)) {
             valid = (nframe >= 1);
@@ -1369,9 +1369,9 @@ pymain_init_tracemalloc(_PyMain *pymain)
         pymain->core_config.tracemalloc = nframe;
     }
 
-    wchar_t *xoption = pymain_get_xoption(pymain, L"tracemalloc");
+    const wchar_t *xoption = pymain_get_xoption(pymain, L"tracemalloc");
     if (xoption) {
-        wchar_t *sep = wcschr(xoption, L'=');
+        const wchar_t *sep = wcschr(xoption, L'=');
         if (sep) {
             if (!pymain_wstr_to_int(sep + 1, &nframe)) {
                 valid = (nframe >= 1);
@@ -1398,7 +1398,7 @@ pymain_init_tracemalloc(_PyMain *pymain)
 static void
 pymain_set_flag_from_env(int *flag, const char *name)
 {
-    char *var = pymain_get_env_var(name);
+    const char *var = pymain_get_env_var(name);
     if (!var) {
         return;
     }
@@ -1449,7 +1449,7 @@ config_get_env_var_dup(wchar_t **dest, wchar_t *wname, char *name)
     }
 
 #ifdef MS_WINDOWS
-    wchar_t *var = _wgetenv(wname);
+    const wchar_t *var = _wgetenv(wname);
     if (!var || var[0] == '\0') {
         *dest = NULL;
         return 0;
@@ -1462,7 +1462,7 @@ config_get_env_var_dup(wchar_t **dest, wchar_t *wname, char *name)
 
     *dest = copy;
 #else
-    char *var = getenv(name);
+    const char *var = getenv(name);
     if (!var || var[0] == '\0') {
         *dest = NULL;
         return 0;
diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c
index c065541458b..0b8816cc54f 100644
--- a/Objects/obmalloc.c
+++ b/Objects/obmalloc.c
@@ -1167,7 +1167,7 @@ new_arena(void)
     static int debug_stats = -1;
 
     if (debug_stats == -1) {
-        char *opt = Py_GETENV("PYTHONMALLOCSTATS");
+        const char *opt = Py_GETENV("PYTHONMALLOCSTATS");
         debug_stats = (opt != NULL && *opt != '\0');
     }
     if (debug_stats)
diff --git a/PC/getpathp.c b/PC/getpathp.c
index 08ed8ccc83f..e142e365052 100644
--- a/PC/getpathp.c
+++ b/PC/getpathp.c
@@ -118,8 +118,8 @@
 #endif
 
 typedef struct {
-    wchar_t *path_env;                 /* PATH environment variable */
-    wchar_t *home;                     /* PYTHONHOME environment variable */
+    const wchar_t *path_env;           /* PATH environment variable */
+    const wchar_t *home;               /* PYTHONHOME environment variable */
 
     /* Registry key "Software\Python\PythonCore\PythonPath" */
     wchar_t *machine_path;   /* from HKEY_LOCAL_MACHINE */
@@ -191,7 +191,7 @@ change_ext(wchar_t *dest, const wchar_t *src, const wchar_t *ext)
 
 
 static int
-exists(wchar_t *filename)
+exists(const wchar_t *filename)
 {
     return GetFileAttributesW(filename) != 0xFFFFFFFF;
 }
@@ -286,7 +286,7 @@ gotlandmark(wchar_t *prefix, const wchar_t *landmark)
 /* assumes argv0_path is MAXPATHLEN+1 bytes long, already \0 term'd.
    assumption provided by only caller, calculate_path_impl() */
 static int
-search_for_prefix(wchar_t *prefix, wchar_t *argv0_path, const wchar_t *landmark)
+search_for_prefix(wchar_t *prefix, const wchar_t *argv0_path, const wchar_t *landmark)
 {
     /* Search from argv0_path, until landmark is found */
     wcscpy_s(prefix, MAXPATHLEN + 1, argv0_path);
@@ -523,9 +523,9 @@ get_program_full_path(const _PyMainInterpreterConfig *main_config,
         wcsncpy(program_full_path, main_config->program_name, MAXPATHLEN);
     }
     else if (calculate->path_env) {
-        wchar_t *path = calculate->path_env;
+        const wchar_t *path = calculate->path_env;
         while (1) {
-            wchar_t *delim = wcschr(path, DELIM);
+            const wchar_t *delim = wcschr(path, DELIM);
 
             if (delim) {
                 size_t len = delim - path;
@@ -845,7 +845,7 @@ calculate_module_search_path(const _PyMainInterpreterConfig *main_config,
     /* Calculate size of return buffer */
     size_t bufsz = 0;
     if (calculate->home != NULL) {
-        wchar_t *p;
+        const wchar_t *p;
         bufsz = 1;
         for (p = PYTHONPATH; *p; p++) {
             if (*p == DELIM) {
@@ -922,8 +922,8 @@ calculate_module_search_path(const _PyMainInterpreterConfig *main_config,
             *buf++ = DELIM;
         }
     } else {
-        wchar_t *p = PYTHONPATH;
-        wchar_t *q;
+        const wchar_t *p = PYTHONPATH;
+        const wchar_t *q;
         size_t n;
         for (;;) {
             q = wcschr(p, DELIM);
@@ -967,10 +967,10 @@ calculate_module_search_path(const _PyMainInterpreterConfig *main_config,
     */
     if (prefix[0] == L'\0') {
         wchar_t lookBuf[MAXPATHLEN+1];
-        wchar_t *look = buf - 1; /* 'buf' is at the end of the buffer */
+        const wchar_t *look = buf - 1; /* 'buf' is at the end of the buffer */
         while (1) {
             Py_ssize_t nchars;
-            wchar_t *lookEnd = look;
+            const wchar_t *lookEnd = look;
             /* 'look' will end up one character before the
                start of the path in question - even if this
                is one character before the start of the buffer
diff --git a/Python/bootstrap_hash.c b/Python/bootstrap_hash.c
index 610541d810b..2762f4656e2 100644
--- a/Python/bootstrap_hash.c
+++ b/Python/bootstrap_hash.c
@@ -533,16 +533,16 @@ _PyOS_URandomNonblock(void *buffer, Py_ssize_t size)
     return pyurandom(buffer, size, 0, 1);
 }
 
-int Py_ReadHashSeed(char *seed_text,
+int Py_ReadHashSeed(const char *seed_text,
                     int *use_hash_seed,
                     unsigned long *hash_seed)
 {
     Py_BUILD_ASSERT(sizeof(_Py_HashSecret_t) == sizeof(_Py_HashSecret.uc));
     /* Convert a text seed to a numeric one */
     if (seed_text && *seed_text != '\0' && strcmp(seed_text, "random") != 0) {
-        char *endptr = seed_text;
+        const char *endptr = seed_text;
         unsigned long seed;
-        seed = strtoul(seed_text, &endptr, 10);
+        seed = strtoul(seed_text, (char **)&endptr, 10);
         if (*endptr != '\0'
             || seed > 4294967295UL
             || (errno == ERANGE && seed == ULONG_MAX))
@@ -604,7 +604,7 @@ init_hash_secret(int use_hash_seed,
 _PyInitError
 _Py_HashRandomization_Init(_PyCoreConfig *core_config)
 {
-    char *seed_text;
+    const char *seed_text;
     int use_hash_seed = core_config->use_hash_seed;
     unsigned long hash_seed = core_config->hash_seed;
 
diff --git a/Python/dynamic_annotations.c b/Python/dynamic_annotations.c
index 10511da4661..7febaa09df1 100644
--- a/Python/dynamic_annotations.c
+++ b/Python/dynamic_annotations.c
@@ -120,7 +120,7 @@ static int GetRunningOnValgrind(void) {
 #endif
 
 #ifndef _MSC_VER
-  char *running_on_valgrind_str = getenv("RUNNING_ON_VALGRIND");
+  const char *running_on_valgrind_str = getenv("RUNNING_ON_VALGRIND");
   if (running_on_valgrind_str) {
     return strcmp(running_on_valgrind_str, "0") != 0;
   }
diff --git a/Python/frozenmain.c b/Python/frozenmain.c
index 77602d70fa8..a3b619671bd 100644
--- a/Python/frozenmain.c
+++ b/Python/frozenmain.c
@@ -23,7 +23,7 @@ Py_FrozenMain(int argc, char **argv)
         exit(1);
     }
 
-    char *p;
+    const char *p;
     int i, n, sts = 1;
     int inspect = 0;
     int unbuffered = 0;
diff --git a/Python/pathconfig.c b/Python/pathconfig.c
index 6a03f7dca1b..53ddfc997da 100644
--- a/Python/pathconfig.c
+++ b/Python/pathconfig.c
@@ -168,7 +168,7 @@ Py_SetPath(const wchar_t *path)
 
 
 void
-Py_SetPythonHome(wchar_t *home)
+Py_SetPythonHome(const wchar_t *home)
 {
     if (home == NULL) {
         return;
@@ -189,7 +189,7 @@ Py_SetPythonHome(wchar_t *home)
 
 
 void
-Py_SetProgramName(wchar_t *program_name)
+Py_SetProgramName(const wchar_t *program_name)
 {
     if (program_name == NULL || program_name[0] == L'\0') {
         return;
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 0b3aa98ba2e..fdb09d910da 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -414,7 +414,7 @@ static _LocaleCoercionTarget _TARGET_LOCALES[] = {
     {NULL}
 };
 
-static char *
+static const char *
 get_default_standard_stream_error_handler(void)
 {
     const char *ctype_loc = setlocale(LC_CTYPE, NULL);
@@ -440,7 +440,7 @@ get_default_standard_stream_error_handler(void)
 }
 
 #ifdef PY_COERCE_C_LOCALE
-static const char *_C_LOCALE_COERCION_WARNING =
+static const char _C_LOCALE_COERCION_WARNING[] =
     "Python detected LC_CTYPE=C: LC_CTYPE coerced to %.20s (set another locale "
     "or PYTHONCOERCECLOCALE=0 to disable this locale coercion behavior).\n";
 
@@ -1757,7 +1757,8 @@ init_sys_streams(void)
     PyObject *std = NULL;
     int fd;
     PyObject * encoding_attr;
-    char *pythonioencoding = NULL, *encoding, *errors;
+    char *pythonioencoding = NULL;
+    const char *encoding, *errors;
     _PyInitError res = _Py_INIT_OK();
 
     /* Hack to avoid a nasty recursion issue when Python is invoked
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index eeeaa7240e7..f10099b5232 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -100,7 +100,7 @@ static PyObject *
 sys_breakpointhook(PyObject *self, PyObject **args, Py_ssize_t nargs, PyObject *keywords)
 {
     assert(!PyErr_Occurred());
-    char *envar = Py_GETENV("PYTHONBREAKPOINT");
+    const char *envar = Py_GETENV("PYTHONBREAKPOINT");
 
     if (envar == NULL || strlen(envar) == 0) {
         envar = "pdb.set_trace";
@@ -109,8 +109,8 @@ sys_breakpointhook(PyObject *self, PyObject **args, Py_ssize_t nargs, PyObject *
         /* The breakpoint is explicitly no-op'd. */
         Py_RETURN_NONE;
     }
-    char *last_dot = strrchr(envar, '.');
-    char *attrname = NULL;
+    const char *last_dot = strrchr(envar, '.');
+    const char *attrname = NULL;
     PyObject *modulepath = NULL;
 
     if (last_dot == NULL) {
diff --git a/Python/thread.c b/Python/thread.c
index 7eac836dc16..07743840693 100644
--- a/Python/thread.c
+++ b/Python/thread.c
@@ -61,7 +61,7 @@ void
 PyThread_init_thread(void)
 {
 #ifdef Py_DEBUG
-    char *p = Py_GETENV("PYTHONTHREADDEBUG");
+    const char *p = Py_GETENV("PYTHONTHREADDEBUG");
 
     if (p) {
         if (*p)