From b21043f8ac1aa2aeaaadae4153f4e059aedaf988 Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Wed, 15 Apr 2026 10:02:55 +0900
Subject: Constify pack functions

---
 pack.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/pack.c b/pack.c
index 7e17b016c7..94bb510e0d 100644
--- a/pack.c
+++ b/pack.c
@@ -62,7 +62,7 @@ is_bigendian(void)
 {
     static int init = 0;
     static int endian_value;
-    char *p;
+    const char *p;
 
     if (init) return endian_value;
     init = 1;
@@ -771,7 +771,7 @@ pack_pack(rb_execution_context_t *ec, VALUE ary, VALUE fmt, VALUE buffer)
             /* FALL THROUGH */
           case 'p':		/* pointer to string */
             while (len-- > 0) {
-                char *t = 0;
+                const char *t = 0;
                 from = NEXTFROM;
                 if (!NIL_P(from)) {
                     STR_FROM(from);
@@ -1001,8 +1001,8 @@ static VALUE
 pack_unpack_internal(VALUE str, VALUE fmt, enum unpack_mode mode, long offset)
 {
 #define hexdigits ruby_hexdigits
-    char *s, *send;
-    char *p, *pend;
+    const char *s, *send;
+    const char *p, *pend;
     VALUE ary, associates = Qfalse;
     long len;
     AVOID_CC_BUG long tmp_len;
@@ -1076,7 +1076,7 @@ pack_unpack_internal(VALUE str, VALUE fmt, enum unpack_mode mode, long offset)
             if (len > send - s) len = send - s;
             {
                 long end = len;
-                char *t = s + len - 1;
+                const char *t = s + len - 1;
 
                 while (t >= s) {
                     if (*t != ' ' && *t != '\0') break;
@@ -1089,7 +1089,7 @@ pack_unpack_internal(VALUE str, VALUE fmt, enum unpack_mode mode, long offset)
 
           case 'Z':
             {
-                char *t = s;
+                const char *t = s;
 
                 if (len > send-s) len = send-s;
                 while (t < s+len && *t) t++;
@@ -1523,7 +1523,8 @@ pack_unpack_internal(VALUE str, VALUE fmt, enum unpack_mode mode, long offset)
           case 'M':
             {
                 VALUE buf = rb_str_new(0, send - s);
-                char *ptr = RSTRING_PTR(buf), *ss = s;
+                char *ptr = RSTRING_PTR(buf);
+                const char *ss = s;
                 int csum = 0;
                 int c1, c2;
 
@@ -1578,7 +1579,7 @@ pack_unpack_internal(VALUE str, VALUE fmt, enum unpack_mode mode, long offset)
           case 'P':
             if (sizeof(char *) <= (size_t)(send - s)) {
                 VALUE tmp = Qnil;
-                char *t;
+                const char *t;
 
                 UNPACK_FETCH(&t, char *);
                 if (t) {
@@ -1601,7 +1602,7 @@ pack_unpack_internal(VALUE str, VALUE fmt, enum unpack_mode mode, long offset)
                     break;
                 else {
                     VALUE tmp = Qnil;
-                    char *t;
+                    const char *t;
 
                     UNPACK_FETCH(&t, char *);
                     if (t) {
@@ -1621,7 +1622,7 @@ pack_unpack_internal(VALUE str, VALUE fmt, enum unpack_mode mode, long offset)
                 if (type == 'r') {
                     pack_flags |= INTEGER_PACK_2COMP;
                 }
-                char *s0 = s;
+                const char *s0 = s;
                 while (len > 0 && s < send) {
                     if (*s & 0x80) {
                         s++;
@@ -1648,7 +1649,7 @@ pack_unpack_internal(VALUE str, VALUE fmt, enum unpack_mode mode, long offset)
 
           case 'w':
             {
-                char *s0 = s;
+                const char *s0 = s;
                 while (len > 0 && s < send) {
                     if (*s & 0x80) {
                         s++;
-- 
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