Add the const qualifier to "char *" variables that refer to literal strings. (#4370)

Author: serhiy-storchaka

Modules/_ctypes/callproc.c

@@ -1336,7 +1336,7 @@ static PyObject *py_dl_open(PyObject *self, PyObject *args)
     handle = ctypes_dlopen(name_str, mode);
     Py_XDECREF(name2);
     if (!handle) {
-        char *errmsg = ctypes_dlerror();
+        const char *errmsg = ctypes_dlerror();
         if (!errmsg)
             errmsg = "dlopen() error";
         PyErr_SetString(PyExc_OSError,

Modules/_cursesmodule.c

@@ -96,7 +96,7 @@
 
 /* Release Number */
 
-char *PyCursesVersion = "2.2";
+static const char PyCursesVersion[] = "2.2";
 
 /* Includes */
 
@@ -2562,7 +2562,7 @@ PyCurses_setupterm(PyObject* self, PyObject *args, PyObject* keywds)
     }
 
     if (!initialised_setupterm && setupterm(termstr,fd,&err) == ERR) {
-        char* s = "setupterm: unknown error";
+        const char* s = "setupterm: unknown error";
 
         if (err == 0) {
             s = "setupterm: could not find terminal";

Modules/_sqlite/connection.c

@@ -1550,7 +1550,7 @@ static PyObject *
 pysqlite_connection_exit(pysqlite_Connection* self, PyObject* args)
 {
     PyObject* exc_type, *exc_value, *exc_tb;
-    char* method_name;
+    const char* method_name;
     PyObject* result;
 
     if (!PyArg_ParseTuple(args, "OOO", &exc_type, &exc_value, &exc_tb)) {

Modules/_testcapimodule.c

@@ -2413,7 +2413,7 @@ test_with_docstring(PyObject *self)
 static PyObject *
 test_string_to_double(PyObject *self) {
     double result;
-    char *msg;
+    const char *msg;
 
 #define CHECK_STRING(STR, expected)                             \
     result = PyOS_string_to_double(STR, NULL, NULL);            \

Modules/fpectlmodule.c

@@ -125,7 +125,8 @@ static void fpe_reset(Sigfunc *handler)
     extern long ieee_handler(const char*, const char*, sigfpe_handler_type);
 #endif
 
-    char *mode="exception", *in="all", *out;
+    const char *mode="exception", *in="all";
+    char *out;
     (void) nonstandard_arithmetic();
     (void) ieee_flags("clearall",mode,in,&out);
     (void) ieee_handler("set","common",(sigfpe_handler_type)handler);

Modules/gcmodule.c

@@ -1608,7 +1608,7 @@ _PyGC_DumpShutdownStats(void)
 {
     if (!(_PyRuntime.gc.debug & DEBUG_SAVEALL)
         && _PyRuntime.gc.garbage != NULL && PyList_GET_SIZE(_PyRuntime.gc.garbage) > 0) {
-        char *message;
+        const char *message;
         if (_PyRuntime.gc.debug & DEBUG_UNCOLLECTABLE)
             message = "gc: %zd uncollectable objects at " \
                 "shutdown";

Modules/getaddrinfo.c

@@ -342,7 +342,7 @@ getaddrinfo(const char*hostname, const char*servname,
             port = htons((u_short)atoi(servname));
         } else {
             struct servent *sp;
-            char *proto;
+            const char *proto;
 
             proto = NULL;
             switch (pai->ai_socktype) {

Modules/main.c

@@ -312,7 +312,7 @@ static int
 run_file(FILE *fp, const wchar_t *filename, PyCompilerFlags *p_cf)
 {
     PyObject *unicode, *bytes = NULL;
-    char *filename_str;
+    const char *filename_str;
     int run;
 
     /* call pending calls like signal handlers (SIGINT) */

Modules/mmapmodule.c

@@ -1210,7 +1210,7 @@ new_mmap_object(PyTypeObject *type, PyObject *args, PyObject *kwdict)
     DWORD off_lo;       /* lower 32 bits of offset */
     DWORD size_hi;      /* upper 32 bits of size */
     DWORD size_lo;      /* lower 32 bits of size */
-    char *tagname = "";
+    const char *tagname = "";
     DWORD dwErr = 0;
     int fileno;
     HANDLE fh = 0;

Modules/ossaudiodev.c

@@ -53,7 +53,7 @@ typedef unsigned long uint32_t;
 
 typedef struct {
     PyObject_HEAD
-    char    *devicename;              /* name of the device file */
+    const char *devicename;           /* name of the device file */
     int      fd;                      /* file descriptor */
     int      mode;                    /* file mode (O_RDONLY, etc.) */
     Py_ssize_t icount;                /* input count */
@@ -82,8 +82,8 @@ newossobject(PyObject *arg)
 {
     oss_audio_t *self;
     int fd, afmts, imode;
-    char *devicename = NULL;
-    char *mode = NULL;
+    const char *devicename = NULL;
+    const char *mode = NULL;
 
     /* Two ways to call open():
          open(device, mode) (for consistency with builtin open())
@@ -167,7 +167,7 @@ oss_dealloc(oss_audio_t *self)
 static oss_mixer_t *
 newossmixerobject(PyObject *arg)
 {
-    char *devicename = NULL;
+    const char *devicename = NULL;
     int fd;
     oss_mixer_t *self;