From 1910bd42477f928b539f09c7ba2ac444bd368fd4 Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Tue, 7 Nov 2023 23:26:14 +0900
Subject: [PATCH] String for string literal is not resizable

---
 ext/-test-/string/depend          |  3 +++
 ext/-test-/string/fstring.c       | 10 ++++++++++
 string.c                          |  2 +-
 test/-ext-/string/test_fstring.rb |  4 ++++
 4 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/ext/-test-/string/depend b/ext/-test-/string/depend
index 26720282b2dabf..eeb4914346bd91 100644
--- a/ext/-test-/string/depend
+++ b/ext/-test-/string/depend
@@ -1196,6 +1196,7 @@ fstring.o: $(hdrdir)/ruby/backward.h
 fstring.o: $(hdrdir)/ruby/backward/2/assume.h
 fstring.o: $(hdrdir)/ruby/backward/2/attributes.h
 fstring.o: $(hdrdir)/ruby/backward/2/bool.h
+fstring.o: $(hdrdir)/ruby/backward/2/gcc_version_since.h
 fstring.o: $(hdrdir)/ruby/backward/2/inttypes.h
 fstring.o: $(hdrdir)/ruby/backward/2/limits.h
 fstring.o: $(hdrdir)/ruby/backward/2/long_long.h
@@ -1358,6 +1359,8 @@ fstring.o: $(hdrdir)/ruby/oniguruma.h
 fstring.o: $(hdrdir)/ruby/ruby.h
 fstring.o: $(hdrdir)/ruby/st.h
 fstring.o: $(hdrdir)/ruby/subst.h
+fstring.o: $(top_srcdir)/internal/compilers.h
+fstring.o: $(top_srcdir)/internal/string.h
 fstring.o: fstring.c
 init.o: $(RUBY_EXTCONF_H)
 init.o: $(arch_hdrdir)/ruby/config.h
diff --git a/ext/-test-/string/fstring.c b/ext/-test-/string/fstring.c
index 2374319fe340b0..7ee14a8570f7d0 100644
--- a/ext/-test-/string/fstring.c
+++ b/ext/-test-/string/fstring.c
@@ -1,5 +1,6 @@
 #include "ruby.h"
 #include "ruby/encoding.h"
+#include "internal/string.h"
 
 VALUE rb_fstring(VALUE str);
 
@@ -9,6 +10,14 @@ bug_s_fstring(VALUE self, VALUE str)
     return rb_fstring(str);
 }
 
+VALUE
+bug_s_fstring_fake_str(VALUE self)
+{
+    static const char literal[] = "abcdefghijklmnopqrstuvwxyz";
+    struct RString fake_str;
+    return rb_fstring(rb_setup_fake_str(&fake_str, literal, sizeof(literal) - 1, 0));
+}
+
 VALUE
 bug_s_rb_enc_interned_str(VALUE self, VALUE encoding)
 {
@@ -25,6 +34,7 @@ void
 Init_string_fstring(VALUE klass)
 {
     rb_define_singleton_method(klass, "fstring", bug_s_fstring, 1);
+    rb_define_singleton_method(klass, "fstring_fake_str", bug_s_fstring_fake_str, 0);
     rb_define_singleton_method(klass, "rb_enc_interned_str", bug_s_rb_enc_interned_str, 1);
     rb_define_singleton_method(klass, "rb_enc_str_new", bug_s_rb_enc_str_new, 1);
 }
diff --git a/string.c b/string.c
index 13b63f023a5a39..b3004624ddc16f 100644
--- a/string.c
+++ b/string.c
@@ -428,7 +428,7 @@ rb_fstring(VALUE str)
         }
     }
 
-    if (!OBJ_FROZEN(str))
+    if (!FL_TEST_RAW(str, FL_FREEZE | STR_NOFREE))
         rb_str_resize(str, RSTRING_LEN(str));
 
     fstr = register_fstring(str, FALSE);
diff --git a/test/-ext-/string/test_fstring.rb b/test/-ext-/string/test_fstring.rb
index 5a3456c5664c33..b7416ccbf37d95 100644
--- a/test/-ext-/string/test_fstring.rb
+++ b/test/-ext-/string/test_fstring.rb
@@ -49,6 +49,10 @@ def test_singleton_class
     assert_raise(TypeError) {fstr.singleton_class}
   end
 
+  def test_fake_str
+    assert_equal([*"a".."z"].join(""), Bug::String.fstring_fake_str)
+  end
+
   class S < String
   end