Arithmetic expression: interest in unsigned right shift?

[Steffen Nurpmeso]

Hello.

I realized there is no unsigned right shift in bash arithmetic
expression, and thought maybe there is interest.
This is a not even compile-tested diff against 5.1.16.
(Using same tab/space as in surroundings.)

A nice Sunday i wish everyone.

diff -Napru bash-5.1.orig/expr.c bash-5.1/expr.c
--- bash-5.1.orig/expr.c        2022-07-16 19:35:21.900221532 +0200
+++ bash-5.1/expr.c     2022-07-16 19:37:23.243552559 +0200
@@ -32,7 +32,7 @@
        "**"                    [(exponentiation)]
        "*", "/", "%"
        "+", "-"
-       "<<", ">>"
+       "<<", ">>", ">>>"
        "<=", ">=", "<", ">"
        "==", "!="
        "&"
@@ -41,7 +41,7 @@
        "&&"
        "||"
        "expr ? expr : expr"
-       "=", "*=", "/=", "%=", "+=", "-=", "<<=", ">>=", "&=", "^=", "|="
+       "=", "*=", "/=", "%=", "+=", "-=", "<<=", ">>=", ">>>=", "&=","^=","|="
        ,                       [comma]
 
  (Note that most of these operators have special meaning to bash, and an
@@ -112,13 +112,14 @@
 #define LOR    8       /* "||" Logical OR */
 #define LSH    9       /* "<<" Left SHift */
 #define RSH    10      /* ">>" Right SHift */
-#define OP_ASSIGN 11   /* op= expassign as in Posix.2 */
-#define COND   12      /* exp1 ? exp2 : exp3 */
-#define POWER  13      /* exp1**exp2 */
-#define PREINC 14      /* ++var */
-#define PREDEC 15      /* --var */
-#define POSTINC        16      /* var++ */
-#define POSTDEC        17      /* var-- */
+#define URSH   11      /* ">>>" Unsigned right SHift */
+#define OP_ASSIGN 12   /* op= expassign as in Posix.2 */
+#define COND   13      /* exp1 ? exp2 : exp3 */
+#define POWER  14      /* exp1**exp2 */
+#define PREINC 15      /* ++var */
+#define PREDEC 16      /* --var */
+#define POSTINC        17      /* var++ */
+#define POSTDEC        18      /* var-- */
 #define EQ     '='
 #define GT     '>'
 #define LT     '<'
@@ -578,6 +579,9 @@ expassign ()
            case RSH:
              lvalue >>= value;
              break;
+           case URSH:
+             lvalue = (uintmax_t)lvalue >> value;
+             break;
            case BAND:
              lvalue &= value;
              break;
@@ -837,7 +841,7 @@ expshift ()
 
   val1 = exp3 ();
 
-  while ((curtok == LSH) || (curtok == RSH))
+  while ((curtok == LSH) || (curtok == RSH) || (curtok == URSH))
     {
       int op = curtok;
 
@@ -846,8 +850,10 @@ expshift ()
 
       if (op == LSH)
        val1 = val1 << val2;
-      else
+      else if (op == RSH)
        val1 = val1 >> val2;
+      else
+       val1 = (uintmax_t)val1 >> val2;
       lasttok = NUM;
     }
 
@@ -1251,6 +1257,7 @@ _is_multiop (c)
     case LOR:
     case LSH:
     case RSH:
+    case URSH:
     case OP_ASSIGN:
     case COND:
     case POWER:
@@ -1424,7 +1431,19 @@ readtok ()
        }
       else if ((c == GT) && (c1 == GT))
        {
-         if (*cp == '=')
+         if (*cp == GT)
+           {
+             cp++;
+             if (*cp == '=')
+               {
+                 assigntok = URSH;     /* a >>>= b */
+                 c = OP_ASSIGN;
+                 cp++;
+               }
+             else
+               c = URSH;
+           }
+         else if (*cp == '=')
            {
              assigntok = RSH;  /* a >>= b */
              c = OP_ASSIGN;

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)