Issue #18722: Remove uses of the "register" keyword in C code.

Python/ceval.c

@@ -37,7 +37,7 @@ typedef unsigned long long uint64;
 static void
 ppc_getcounter(uint64 *v)
 {
-    register unsigned long tbu, tb, tbu2;
+    unsigned long tbu, tb, tbu2;
 
   loop:
     asm volatile ("mftbu %0" : "=r" (tbu) );
@@ -792,12 +792,12 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
 #ifdef DXPAIRS
     int lastopcode = 0;
 #endif
-    register PyObject **stack_pointer;  /* Next free slot in value stack */
-    register unsigned char *next_instr;
-    register int opcode;        /* Current opcode */
-    register int oparg;         /* Current opcode argument, if any */
-    register enum why_code why; /* Reason for block stack unwind */
-    register PyObject **fastlocals, **freevars;
+    PyObject **stack_pointer;  /* Next free slot in value stack */
+    unsigned char *next_instr;
+    int opcode;        /* Current opcode */
+    int oparg;         /* Current opcode argument, if any */
+    enum why_code why; /* Reason for block stack unwind */
+    PyObject **fastlocals, **freevars;
     PyObject *retval = NULL;            /* Return value */
     PyThreadState *tstate = PyThreadState_GET();
     PyCodeObject *co;
@@ -3373,9 +3373,9 @@ PyEval_EvalCodeEx(PyObject *_co, PyObject *globals, PyObject *locals,
            PyObject **defs, int defcount, PyObject *kwdefs, PyObject *closure)
 {
     PyCodeObject* co = (PyCodeObject*)_co;
-    register PyFrameObject *f;
-    register PyObject *retval = NULL;
-    register PyObject **fastlocals, **freevars;
+    PyFrameObject *f;
+    PyObject *retval = NULL;
+    PyObject **fastlocals, **freevars;
     PyThreadState *tstate = PyThreadState_GET();
     PyObject *x, *u;
     int total_args = co->co_argcount + co->co_kwonlyargcount;
@@ -3895,7 +3895,7 @@ static int
 call_trace(Py_tracefunc func, PyObject *obj, PyFrameObject *frame,
            int what, PyObject *arg)
 {
-    register PyThreadState *tstate = frame->f_tstate;
+    PyThreadState *tstate = frame->f_tstate;
     int result;
     if (tstate->tracing)
         return 0;
@@ -4581,7 +4581,7 @@ _PyEval_SliceIndex(PyObject *v, Py_ssize_t *pi)
                          "BaseException is not allowed"
 
 static PyObject *
-cmp_outcome(int op, register PyObject *v, register PyObject *w)
+cmp_outcome(int op, PyObject *v, PyObject *w)
 {
     int res = 0;
     switch (op) {

Python/codecs.c

@@ -53,7 +53,7 @@ int PyCodec_Register(PyObject *search_function)
 static
 PyObject *normalizestring(const char *string)
 {
-    register size_t i;
+    size_t i;
     size_t len = strlen(string);
     char *p;
     PyObject *v;
@@ -67,7 +67,7 @@ PyObject *normalizestring(const char *string)
     if (p == NULL)
         return PyErr_NoMemory();
     for (i = 0; i < len; i++) {
-        register char ch = string[i];
+        char ch = string[i];
         if (ch == ' ')
             ch = '-';
         else

Python/dynload_aix.c

@@ -30,11 +30,11 @@ const char *_PyImport_DynLoadFiletab[] = {".so", NULL};
 static int
 aix_getoldmodules(void **modlistptr)
 {
-    register ModulePtr       modptr, prevmodptr;
-    register struct ld_info  *ldiptr;
-    register char            *ldibuf;
-    register int             errflag, bufsize = 1024;
-    register unsigned int    offset;
+    ModulePtr       modptr, prevmodptr;
+    struct ld_info  *ldiptr;
+    char            *ldibuf;
+    int             errflag, bufsize = 1024;
+    unsigned int    offset;
     char *progname = Py_GetProgramName();
 
     /*
@@ -106,7 +106,7 @@ aix_loaderror(const char *pathname)
     char *message[1024], errbuf[1024];
     PyObject *pathname_ob = NULL;
     PyObject *errbuf_ob = NULL;
-    register int i,j;
+    int i,j;
 
     struct errtab {
         int errNo;

Python/marshal.c

@@ -613,7 +613,7 @@ r_byte(RFILE *p)
 static int
 r_short(RFILE *p)
 {
-    register short x;
+    short x;
     unsigned char buffer[2];
 
     r_string((char *) buffer, 2, p);
@@ -627,7 +627,7 @@ r_short(RFILE *p)
 static long
 r_long(RFILE *p)
 {
-    register long x;
+    long x;
     unsigned char buffer[4];
 
     r_string((char *) buffer, 4, p);

Python/mystrtoul.c

@@ -92,11 +92,11 @@ static int digitlimit[] = {
 **              exceptions - we don't check for them.
 */
 unsigned long
-PyOS_strtoul(register char *str, char **ptr, int base)
+PyOS_strtoul(char *str, char **ptr, int base)
 {
-    register unsigned long result = 0; /* return value of the function */
-    register int c;             /* current input character */
-    register int ovlimit;       /* required digits to overflow */
+    unsigned long result = 0; /* return value of the function */
+    int c;             /* current input character */
+    int ovlimit;       /* required digits to overflow */
 
     /* skip leading white space */
     while (*str && Py_ISSPACE(Py_CHARMASK(*str)))
@@ -213,7 +213,7 @@ PyOS_strtoul(register char *str, char **ptr, int base)
         if (ovlimit > 0) /* no overflow check required */
             result = result * base + c;
         else { /* requires overflow check */
-            register unsigned long temp_result;
+            unsigned long temp_result;
 
             if (ovlimit < 0) /* guaranteed overflow */
                 goto overflowed;

Python/strdup.c

@@ -6,7 +6,7 @@ char *
 strdup(const char *str)
 {
 	if (str != NULL) {
-		register char *copy = malloc(strlen(str) + 1);
+		char *copy = malloc(strlen(str) + 1);
 		if (copy != NULL)
 			return strcpy(copy, str);
 	}