Prohibit string changes by "s"/"z" specifier of `mrb_get_args()`

- The `s` specifier is a string pointer obtained without performing `mrb_str_modify()`, so it cannot be changed.
- The `z` specifier cannot be changed because it is a string pointer obtained by `RSTRING_CSTR()` which returns `const char *`.

1 files changed, 6 insertions, 4 deletions

diff --git a/mrbgems/mruby-string-ext/src/string.c b/mrbgems/mruby-string-ext/src/string.c
index 7cf146ec8..ded34a89e 100644
--- a/mrbgems/mruby-string-ext/src/string.c
+++ b/mrbgems/mruby-string-ext/src/string.c
@@ -1072,7 +1072,8 @@ static mrb_value
 mrb_str_del_prefix_bang(mrb_state *mrb, mrb_value self)
 {
   mrb_int plen, slen;
-  char *ptr, *s;
+  const char *ptr;
+  char *s;
   struct RString *str = RSTRING(self);
 
   mrb_get_args(mrb, "s", &ptr, &plen);
@@ -1105,7 +1106,7 @@ static mrb_value
 mrb_str_del_prefix(mrb_state *mrb, mrb_value self)
 {
   mrb_int plen, slen;
-  char *ptr;
+  const char *ptr;
 
   mrb_get_args(mrb, "s", &ptr, &plen);
   slen = RSTRING_LEN(self);
@@ -1129,7 +1130,8 @@ static mrb_value
 mrb_str_del_suffix_bang(mrb_state *mrb, mrb_value self)
 {
   mrb_int plen, slen;
-  char *ptr, *s;
+  const char *ptr;
+  char *s;
   struct RString *str = RSTRING(self);
 
   mrb_get_args(mrb, "s", &ptr, &plen);
@@ -1160,7 +1162,7 @@ static mrb_value
 mrb_str_del_suffix(mrb_state *mrb, mrb_value self)
 {
   mrb_int plen, slen;
-  char *ptr;
+  const char *ptr;
 
   mrb_get_args(mrb, "s", &ptr, &plen);
   slen = RSTRING_LEN(self);