diff --git a/.github/workflows/codeql-analysis.yml b/.github/workflows/codeql-analysis.yml
index 0b4103913bcae5..3ac1ed59cb2b5f 100644
--- a/.github/workflows/codeql-analysis.yml
+++ b/.github/workflows/codeql-analysis.yml
@@ -75,17 +75,17 @@ jobs:
         run: sudo rm /usr/lib/ruby/vendor_ruby/rubygems/defaults/operating_system.rb
 
       - name: Initialize CodeQL
-        uses: github/codeql-action/init@df409f7d9260372bd5f19e5b04e83cb3c43714ae # v3.27.9
+        uses: github/codeql-action/init@e296a935590eb16afc0c0108289f68c87e2a89a5 # v4.30.7
         with:
           languages: ${{ matrix.language }}
           trap-caching: false
           debug: true
 
       - name: Autobuild
-        uses: github/codeql-action/autobuild@df409f7d9260372bd5f19e5b04e83cb3c43714ae # v3.27.9
+        uses: github/codeql-action/autobuild@e296a935590eb16afc0c0108289f68c87e2a89a5 # v4.30.7
 
       - name: Perform CodeQL Analysis
-        uses: github/codeql-action/analyze@df409f7d9260372bd5f19e5b04e83cb3c43714ae # v3.27.9
+        uses: github/codeql-action/analyze@e296a935590eb16afc0c0108289f68c87e2a89a5 # v4.30.7
         with:
           category: '/language:${{ matrix.language }}'
           upload: False
@@ -115,7 +115,7 @@ jobs:
         continue-on-error: true
 
       - name: Upload SARIF
-        uses: github/codeql-action/upload-sarif@df409f7d9260372bd5f19e5b04e83cb3c43714ae # v3.27.9
+        uses: github/codeql-action/upload-sarif@e296a935590eb16afc0c0108289f68c87e2a89a5 # v4.30.7
         with:
           sarif_file: sarif-results/${{ matrix.language }}.sarif
         continue-on-error: true
diff --git a/.github/workflows/post_push.yml b/.github/workflows/post_push.yml
index e252239c3fbf4e..32d74f644e6bf0 100644
--- a/.github/workflows/post_push.yml
+++ b/.github/workflows/post_push.yml
@@ -22,6 +22,13 @@ jobs:
           RUBY_GIT_SYNC_PRIVATE_KEY: ${{ secrets.RUBY_GIT_SYNC_PRIVATE_KEY }}
         if: ${{ github.ref == 'refs/heads/master' || startsWith(github.ref, 'refs/heads/ruby_') }}
 
+      - name: Fetch changesets on bugs.ruby-lang.org
+        run: |
+          curl "https://bugs.ruby-lang.org/sys/fetch_changesets?key=${REDMINE_SYS_API_KEY}" -s --fail-with-body -w '* status: %{http_code}\n'
+        env:
+          REDMINE_SYS_API_KEY: ${{ secrets.REDMINE_SYS_API_KEY }}
+        if: ${{ github.ref == 'refs/heads/master' || startsWith(github.ref, 'refs/heads/ruby_') }}
+
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
         with:
           fetch-depth: 500 # for notify-slack-commits
diff --git a/.github/workflows/scorecards.yml b/.github/workflows/scorecards.yml
index 99c563a25b3728..34a301ddb020d5 100644
--- a/.github/workflows/scorecards.yml
+++ b/.github/workflows/scorecards.yml
@@ -73,6 +73,6 @@ jobs:
       # Upload the results to GitHub's code scanning dashboard (optional).
       # Commenting out will disable upload of results to your repo's Code Scanning dashboard
       - name: "Upload to code-scanning"
-        uses: github/codeql-action/upload-sarif@v3
+        uses: github/codeql-action/upload-sarif@v4
         with:
           sarif_file: results.sarif
diff --git a/error.c b/error.c
index c510432c9d8ae4..2f24929d44ea91 100644
--- a/error.c
+++ b/error.c
@@ -2619,7 +2619,7 @@ name_err_mesg_to_str(VALUE obj)
     VALUE mesg = ptr->mesg;
     if (NIL_P(mesg)) return Qnil;
     else {
-        struct RString s_str, c_str, d_str;
+        struct RString s_str = {RBASIC_INIT}, c_str = {RBASIC_INIT}, d_str = {RBASIC_INIT};
         VALUE c, s, d = 0, args[4], c2;
         int state = 0;
         rb_encoding *usascii = rb_usascii_encoding();
diff --git a/ext/-test-/string/fstring.c b/ext/-test-/string/fstring.c
index 71c4b7f97eee44..92a846a93c2e5c 100644
--- a/ext/-test-/string/fstring.c
+++ b/ext/-test-/string/fstring.c
@@ -12,7 +12,7 @@ VALUE
 bug_s_fstring_fake_str(VALUE self)
 {
     static const char literal[] = "abcdefghijklmnopqrstuvwxyz";
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     return rb_str_to_interned_str(rb_setup_fake_str(&fake_str, literal, sizeof(literal) - 1, 0));
 }
 
diff --git a/include/ruby/internal/attr/nonstring.h b/include/ruby/internal/attr/nonstring.h
index 9a66180e19e2d2..5ad6ef2a86507e 100644
--- a/include/ruby/internal/attr/nonstring.h
+++ b/include/ruby/internal/attr/nonstring.h
@@ -27,6 +27,8 @@
 # define RBIMPL_ATTR_NONSTRING() __attribute__((nonstring))
 # if RBIMPL_COMPILER_SINCE(GCC, 15, 0, 0)
 #   define RBIMPL_ATTR_NONSTRING_ARRAY() RBIMPL_ATTR_NONSTRING()
+# elif RBIMPL_COMPILER_SINCE(Clang, 21, 0, 0)
+#   define RBIMPL_ATTR_NONSTRING_ARRAY() RBIMPL_ATTR_NONSTRING()
 # else
 #   define RBIMPL_ATTR_NONSTRING_ARRAY() /* void */
 # endif
diff --git a/include/ruby/internal/core/rbasic.h b/include/ruby/internal/core/rbasic.h
index 35af03f7c807e3..63cdff8e09586c 100644
--- a/include/ruby/internal/core/rbasic.h
+++ b/include/ruby/internal/core/rbasic.h
@@ -115,6 +115,9 @@ RBasic {
 #endif
     {
     }
+# define RBASIC_INIT RBasic()
+#else
+# define RBASIC_INIT {RBIMPL_VALUE_NULL}
 #endif
 };
 
diff --git a/include/ruby/internal/core/rstring.h b/include/ruby/internal/core/rstring.h
index 0bca74e688fe44..9cf9daa97c87e7 100644
--- a/include/ruby/internal/core/rstring.h
+++ b/include/ruby/internal/core/rstring.h
@@ -395,7 +395,7 @@ rbimpl_rstring_getmem(VALUE str)
     }
     else {
         /* Expecting compilers to optimize this on-stack struct away. */
-        struct RString retval;
+        struct RString retval = {RBASIC_INIT};
         retval.len = RSTRING_LEN(str);
         retval.as.heap.ptr = RSTRING(str)->as.embed.ary;
         return retval;
diff --git a/load.c b/load.c
index 1928721c9e9cb2..9a1ff53f5415da 100644
--- a/load.c
+++ b/load.c
@@ -1434,7 +1434,7 @@ rb_require_internal(VALUE fname)
 int
 ruby_require_internal(const char *fname, unsigned int len)
 {
-    struct RString fake;
+    struct RString fake = {RBASIC_INIT};
     VALUE str = rb_setup_fake_str(&fake, fname, len, 0);
     rb_execution_context_t *ec = GET_EC();
     int result = require_internal(ec, str, 0, RTEST(ruby_verbose));
@@ -1476,7 +1476,7 @@ rb_require_string_internal(VALUE fname, bool resurrect)
 VALUE
 rb_require(const char *fname)
 {
-    struct RString fake;
+    struct RString fake = {RBASIC_INIT};
     VALUE str = rb_setup_fake_str(&fake, fname, strlen(fname), 0);
     return rb_require_string_internal(str, true);
 }
diff --git a/marshal.c b/marshal.c
index f7474ca60edf07..4372960a7190ef 100644
--- a/marshal.c
+++ b/marshal.c
@@ -1428,7 +1428,7 @@ long
 ruby_marshal_read_long(const char **buf, long len)
 {
     long x;
-    struct RString src;
+    struct RString src = {RBASIC_INIT};
     struct load_arg arg;
     memset(&arg, 0, sizeof(arg));
     arg.src = rb_setup_fake_str(&src, *buf, len, 0);
diff --git a/string.c b/string.c
index a31aaece18f7a1..331f48313600f4 100644
--- a/string.c
+++ b/string.c
@@ -655,14 +655,14 @@ rb_setup_fake_str(struct RString *fake_str, const char *name, long len, rb_encod
 VALUE
 rb_fstring_new(const char *ptr, long len)
 {
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     return register_fstring(setup_fake_str(&fake_str, ptr, len, ENCINDEX_US_ASCII), false, false);
 }
 
 VALUE
 rb_fstring_enc_new(const char *ptr, long len, rb_encoding *enc)
 {
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     return register_fstring(rb_setup_fake_str(&fake_str, ptr, len, enc), false, false);
 }
 
@@ -6497,7 +6497,7 @@ str_gsub(int argc, VALUE *argv, VALUE str, int bang)
                 val = rb_obj_as_string(rb_yield(match0));
             }
             else {
-                struct RString fake_str;
+                struct RString fake_str = {RBASIC_INIT};
                 VALUE key;
                 if (mode == FAST_MAP) {
                     // It is safe to use a fake_str here because we established that it won't escape,
@@ -12747,7 +12747,7 @@ rb_str_to_interned_str(VALUE str)
 VALUE
 rb_interned_str(const char *ptr, long len)
 {
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     return register_fstring(setup_fake_str(&fake_str, ptr, len, ENCINDEX_US_ASCII), true, false);
 }
 
@@ -12764,7 +12764,7 @@ rb_enc_interned_str(const char *ptr, long len, rb_encoding *enc)
         rb_enc_autoload(enc);
     }
 
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     return register_fstring(rb_setup_fake_str(&fake_str, ptr, len, enc), true, false);
 }
 
@@ -12775,7 +12775,7 @@ rb_enc_literal_str(const char *ptr, long len, rb_encoding *enc)
         rb_enc_autoload(enc);
     }
 
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     return register_fstring(rb_setup_fake_str(&fake_str, ptr, len, enc), true, true);
 }
 
diff --git a/symbol.c b/symbol.c
index e8eacd34c2b4b8..a498f742aa1600 100644
--- a/symbol.c
+++ b/symbol.c
@@ -845,7 +845,7 @@ lookup_id_str(ID id)
 ID
 rb_intern3(const char *name, long len, rb_encoding *enc)
 {
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     VALUE str = rb_setup_fake_str(&fake_str, name, len, enc);
     OBJ_FREEZE(str);
 
@@ -1222,7 +1222,7 @@ rb_check_symbol(volatile VALUE *namep)
 ID
 rb_check_id_cstr(const char *ptr, long len, rb_encoding *enc)
 {
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     const VALUE name = rb_setup_fake_str(&fake_str, ptr, len, enc);
 
     sym_check_asciionly(name, true);
@@ -1234,7 +1234,7 @@ VALUE
 rb_check_symbol_cstr(const char *ptr, long len, rb_encoding *enc)
 {
     VALUE sym;
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     const VALUE name = rb_setup_fake_str(&fake_str, ptr, len, enc);
 
     sym_check_asciionly(name, true);
@@ -1258,7 +1258,7 @@ FUNC_MINIMIZED(VALUE rb_sym_intern_ascii_cstr(const char *ptr));
 VALUE
 rb_sym_intern(const char *ptr, long len, rb_encoding *enc)
 {
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     const VALUE name = rb_setup_fake_str(&fake_str, ptr, len, enc);
     return rb_str_intern(name);
 }
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index f4f0314ed90ece..b99ffdc4fdbbe6 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -6428,7 +6428,7 @@ static VALUE
 vm_opt_newarray_include_p(rb_execution_context_t *ec, rb_num_t num, const VALUE *ptr, VALUE target)
 {
     if (BASIC_OP_UNREDEFINED_P(BOP_INCLUDE_P, ARRAY_REDEFINED_OP_FLAG)) {
-        struct RArray fake_ary;
+        struct RArray fake_ary = {RBASIC_INIT};
         VALUE ary = rb_setup_fake_ary(&fake_ary, ptr, num);
         return rb_ary_includes(ary, target);
     }
@@ -6448,7 +6448,7 @@ static VALUE
 vm_opt_newarray_pack_buffer(rb_execution_context_t *ec, rb_num_t num, const VALUE *ptr, VALUE fmt, VALUE buffer)
 {
     if (BASIC_OP_UNREDEFINED_P(BOP_PACK, ARRAY_REDEFINED_OP_FLAG)) {
-        struct RArray fake_ary;
+        struct RArray fake_ary = {RBASIC_INIT};
         VALUE ary = rb_setup_fake_ary(&fake_ary, ptr, num);
         return rb_ec_pack_ary(ec, ary, fmt, (UNDEF_P(buffer) ? Qnil : buffer));
     }