[ruby/bigdecimal] Read version from bigdecimal.c

The dependency of extconf.h on bigdecimal.gemspec does not make sense
as far as no rule is defined for it.  Also, the relationship between
extension library and gemspec file is various in default gems, and
does not work well.

https://github.com/ruby/bigdecimal/commit/7f99b28552

ext/bigdecimal/bigdecimal.c

@@ -31,6 +31,8 @@
 #include "bits.h"
 #include "static_assert.h"
 
+#define BIGDECIMAL_VERSION "3.1.3"
+
 /* #define ENABLE_NUMERIC_STRING */
 
 #define SIGNED_VALUE_MAX INTPTR_MAX
@@ -4402,13 +4404,10 @@ Init_bigdecimal(void)
 
     /* Constants definition */
 
-#ifndef RUBY_BIGDECIMAL_VERSION
-# error RUBY_BIGDECIMAL_VERSION is not defined
-#endif
     /*
      * The version of bigdecimal library
      */
-    rb_define_const(rb_cBigDecimal, "VERSION", rb_str_new2(RUBY_BIGDECIMAL_VERSION));
+    rb_define_const(rb_cBigDecimal, "VERSION", rb_str_new2(BIGDECIMAL_VERSION));
 
     /*
      * Base value used in internal calculations.  On a 32 bit system, BASE

ext/bigdecimal/bigdecimal.gemspec

@@ -1,8 +1,18 @@
 # coding: utf-8
 
+name = File.basename(__FILE__, '.*')
+source_version = ["", "ext/#{name}/"].find do |dir|
+  begin
+    break File.foreach(File.join(__dir__, "#{dir}#{name}.c")) {|line|
+      break $1.sub("-", ".") if /^#define\s+#{name.upcase}_VERSION\s+"(.+)"/o =~ line
+    }
+  rescue Errno::ENOENT
+  end
+end or raise "can't find #{name.upcase}_VERSION"
+
 Gem::Specification.new do |s|
-  s.name          = "bigdecimal"
-  s.version       = "3.1.3"
+  s.name          = name
+  s.version       = source_version
   s.authors       = ["Kenta Murata", "Zachary Scott", "Shigeo Kobayashi"]
   s.email         = ["mrkn@mrkn.jp"]
 

ext/bigdecimal/depend

@@ -1,4 +1,3 @@
-extconf.h: $(srcdir)/$(GEMSPEC)
 Makefile: $(BIGDECIMAL_RB)
 
 # AUTOGENERATED DEPENDENCIES START

ext/bigdecimal/extconf.rb

@@ -1,18 +1,6 @@
 # frozen_string_literal: false
 require 'mkmf'
 
-def check_bigdecimal_version(gemspec_path)
-  message "checking RUBY_BIGDECIMAL_VERSION... "
-  bigdecimal_version = File.read(gemspec_path).match(/^\s*s\.version\s+=\s+['"]([^'"]+)['"]\s*$/)[1]
-
-  version_components = bigdecimal_version.split('.')
-  bigdecimal_version = version_components[0, 3].join('.')
-  bigdecimal_version << "-#{version_components[3]}" if version_components[3]
-  $defs << %Q[-DRUBY_BIGDECIMAL_VERSION=\\"#{bigdecimal_version}\\"]
-
-  message "#{bigdecimal_version}\n"
-end
-
 def have_builtin_func(name, check_expr, opt = "", &b)
   checking_for checking_message(name.funcall_style, nil, opt) do
     if try_compile(<<SRC, opt, &b)
@@ -27,18 +15,6 @@ SRC
   end
 end
 
-gemspec_name = gemspec_path = nil
-unless ['', '../../'].any? {|dir|
-         gemspec_name = "#{dir}bigdecimal.gemspec"
-         gemspec_path = File.expand_path("../#{gemspec_name}", __FILE__)
-         File.file?(gemspec_path)
-       }
-  $stderr.puts "Unable to find bigdecimal.gemspec"
-  abort
-end
-
-check_bigdecimal_version(gemspec_path)
-
 have_builtin_func("__builtin_clz", "__builtin_clz(0)")
 have_builtin_func("__builtin_clzl", "__builtin_clzl(0)")
 have_builtin_func("__builtin_clzll", "__builtin_clzll(0)")
@@ -82,6 +58,5 @@ else
 end
 
 create_makefile('bigdecimal') {|mf|
-  mf << "GEMSPEC = #{gemspec_name}\n"
   mf << "BIGDECIMAL_RB = #{bigdecimal_rb}\n"
 }