From bdfc5eba7d7fbbea0a72ebcb67130576d1f69794 Mon Sep 17 00:00:00 2001
From: Chris Seaton <chris.seaton@shopify.com>
Date: Fri, 1 Jul 2022 18:06:32 +0000
Subject: [PATCH] Dynamically create RUBY_DESCRIPTION based on runtime
 parameters

---
 template/fake.rb.in | 20 ++++++++++----------
 version.c           | 30 ++++++++++++++----------------
 version.h           | 13 +++++++------
 3 files changed, 31 insertions(+), 32 deletions(-)

diff --git a/template/fake.rb.in b/template/fake.rb.in
index aead377ed87387..42ddd86d2671c7 100644
--- a/template/fake.rb.in
+++ b/template/fake.rb.in
@@ -17,8 +17,8 @@ if inc = arg['i']
     scan(/rb_define_global_const\("(RUBY_\w+)",[^;]*?\bMK(?:INT|STR)\(([^()]*)\)/m) do |n, v|
     version[n] = src.value(v)
   end
-  arg['RUBY_DESCRIPTION_WITH_MJIT'] = src.value('description_with_mjit')
-  arg['RUBY_DESCRIPTION_WITH_YJIT'] = src.value('description_with_yjit')
+  arg['RUBY_DESCRIPTION_PRE'] = src.value('description_pre')
+  arg['RUBY_DESCRIPTION_POST'] = src.value('description_post')
 end
 %>baseruby="<%=arg['BASERUBY']%>"
 _\
@@ -35,15 +35,15 @@ class Object
   CROSS_COMPILING = RUBY_PLATFORM
   constants.grep(/^RUBY_/) {|n| remove_const n}
 % arg['versions'].each {|n, v|
-  <%=n%> = <%if n=='RUBY_DESCRIPTION' %>case
-    when RubyVM.const_defined?(:MJIT) && RubyVM::MJIT.enabled?
-      <%=arg['RUBY_DESCRIPTION_WITH_MJIT'].inspect%>
-    when RubyVM.const_defined?(:YJIT) && RubyVM::YJIT.enabled?
-      <%=arg['RUBY_DESCRIPTION_WITH_YJIT'].inspect%>
-    else
-      <%=v.inspect%>
-    end<%else%><%=v.inspect%><%end%>
+  <%=n%> = <%=v.inspect%>
 % }
+  options = []
+  if RubyVM.const_defined?(:MJIT) && RubyVM::MJIT.enabled?
+    options << ' +MJIT'
+  elsif RubyVM.const_defined?(:YJIT) && RubyVM::YJIT.enabled?
+    options << ' +YJIT'
+  end
+  RUBY_DESCRIPTION = (<%=arg['RUBY_DESCRIPTION_PRE'].inspect%> + options.join('') + <%=arg['RUBY_DESCRIPTION_POST'].inspect%>).freeze
 end
 builddir = File.dirname(File.expand_path(__FILE__))
 srcdir = "<%=arg['srcdir']%>"
diff --git a/version.c b/version.c
index a628952907d93f..fbfe1c0d34dec8 100644
--- a/version.c
+++ b/version.c
@@ -41,12 +41,15 @@ const char ruby_revision[] = RUBY_FULL_REVISION;
 const char ruby_release_date[] = RUBY_RELEASE_DATE;
 const char ruby_platform[] = RUBY_PLATFORM;
 const int ruby_patchlevel = RUBY_PATCHLEVEL;
-const char ruby_description[] = RUBY_DESCRIPTION_WITH("");
-static const char ruby_description_with_mjit[] = RUBY_DESCRIPTION_WITH(" +MJIT");
-static const char ruby_description_with_yjit[] = RUBY_DESCRIPTION_WITH(" +YJIT");
+const char ruby_description[] = RUBY_DESCRIPTION_PRE RUBY_DESCRIPTION_POST;
+const char ruby_description_pre[] = RUBY_DESCRIPTION_PRE;
+const char ruby_description_post[] = RUBY_DESCRIPTION_POST;
 const char ruby_copyright[] = RUBY_COPYRIGHT;
 const char ruby_engine[] = "ruby";
 
+// Enough space for any combination of option flags
+static char ruby_dynamic_description_buffer[sizeof(ruby_description) + sizeof("+MJIT +YJIT") - 1];
+
 // Might change after initialization
 const char *rb_dynamic_description = ruby_description;
 
@@ -104,24 +107,19 @@ Init_version(void)
 void
 Init_ruby_description(void)
 {
-    VALUE description;
-
-    if (MJIT_OPTS_ON) {
-        rb_dynamic_description = ruby_description_with_mjit;
-        description = MKSTR(description_with_mjit);
-    }
-    else if (rb_yjit_enabled_p()) {
-        rb_dynamic_description = ruby_description_with_yjit;
-        description = MKSTR(description_with_yjit);
-    }
-    else {
-        description = MKSTR(description);
+    if (snprintf(ruby_dynamic_description_buffer, sizeof(ruby_dynamic_description_buffer), "%s%s%s%s",
+            ruby_description_pre,
+            MJIT_OPTS_ON ? " +MJIT" : "",
+            rb_yjit_enabled_p() ? " +YJIT" : "",
+            ruby_description_post) < 0) {
+        rb_bug("could not format dynamic description string");
     }
+    rb_dynamic_description = ruby_dynamic_description_buffer;
 
     /*
      * The full ruby version string, like <tt>ruby -v</tt> prints
      */
-    rb_define_global_const("RUBY_DESCRIPTION", /* MKSTR(description) */ description);
+    rb_define_global_const("RUBY_DESCRIPTION", rb_obj_freeze(rb_str_new2(rb_dynamic_description)));
 }
 
 void
diff --git a/version.h b/version.h
index bf4f22ab975b15..e350e0f7e0433a 100644
--- a/version.h
+++ b/version.h
@@ -76,12 +76,13 @@
 # define RUBY_RELEASE_DATETIME RUBY_RELEASE_DATE
 #endif
 
-# define RUBY_DESCRIPTION_WITH(opt) \
-    "ruby "RUBY_VERSION		    \
-    RUBY_PATCHLEVEL_STR		    \
-    " ("RUBY_RELEASE_DATETIME	    \
-    RUBY_REVISION_STR")"opt" "	    \
-    "["RUBY_PLATFORM"]"
+# define RUBY_DESCRIPTION_PRE \
+    "ruby "RUBY_VERSION             \
+    RUBY_PATCHLEVEL_STR             \
+    " ("RUBY_RELEASE_DATETIME       \
+    RUBY_REVISION_STR")"
+# define RUBY_DESCRIPTION_POST \
+    " ["RUBY_PLATFORM"]"
 # define RUBY_COPYRIGHT		    \
     "ruby - Copyright (C) "	    \
     RUBY_BIRTH_YEAR_STR"-"   \