1 files changed, 11 insertions, 0 deletions
diff --git a/ext/gdbm/extconf.rb b/ext/gdbm/extconf.rb
index 5a09492e5e..389bfb633f 100644
--- a/ext/gdbm/extconf.rb
+++ b/ext/gdbm/extconf.rb
@@ -3,5 +3,16 @@ require 'mkmf'
 dir_config("gdbm")
 if have_library("gdbm", "gdbm_open") and
    have_header("gdbm.h")
+  checking_for("sizeof(DBM) is available") {
+    if try_compile(<<SRC)
+#include <gdbm.h>
+
+const int sizeof_DBM = (int)sizeof(DBM);
+SRC
+      $defs << '-DDBM_SIZEOF_DBM=sizeof(DBM)'
+    else
+      $defs << '-DDBM_SIZEOF_DBM=0'
+    end
+  }
   create_makefile("gdbm")
 end