diff --git a/ChangeLog b/ChangeLog
index 8640355354..658cd99327 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,17 @@
+Fri Nov  9 12:07:06 2012  Akinori MUSHA  <knu@iDaemons.org>
+
+	* include/ruby/ruby.h (alloca), eval_intern.h (alloca), gc.c
+	  (alloca): Make alloca() globally available by moving the
+	  ultimate ifdef's to ruby/ruby.h.  Gcc hides its builtin alloca()
+	  when compiling with -ansi, and linking thus fails on platforms
+	  that lack their own alloca() implementation in libc, which
+	  include OpenBSD and some ports of NetBSD.  We use alloca()
+	  everywhere including from within third party C extentions, so
+	  alloca() must be made globally available. [Bug #7307]
+
+	* addr2line.c (alloca): Replace the alloca() part with the
+	  ultimate ifdef's. [Bug #7307]
+
 Fri Nov  9 09:30:00 2012  Zachary Scott  <zachary@zacharyscott.net>
 
 	* io.c (IO#new):
diff --git a/addr2line.c b/addr2line.c
index 9528a8fa43..e102abba4f 100644
--- a/addr2line.c
+++ b/addr2line.c
@@ -32,9 +32,26 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
-#if defined(HAVE_ALLOCA_H)
-#include <alloca.h>
-#endif
+/* Make alloca work the best possible way.  */
+#ifdef __GNUC__
+# ifndef atarist
+#  ifndef alloca
+#   define alloca __builtin_alloca
+#  endif
+# endif	/* atarist */
+#else
+# ifdef HAVE_ALLOCA_H
+#  include <alloca.h>
+# else
+#  ifdef _AIX
+#pragma alloca
+#  else
+#   ifndef alloca		/* predefined by HP cc +Olibcalls */
+void *alloca();
+#   endif
+#  endif /* AIX */
+# endif	/* HAVE_ALLOCA_H */
+#endif /* __GNUC__ */
 
 #ifdef HAVE_DL_ITERATE_PHDR
 # ifndef _GNU_SOURCE
diff --git a/eval_intern.h b/eval_intern.h
index fb852cbca5..421900b147 100644
--- a/eval_intern.h
+++ b/eval_intern.h
@@ -31,27 +31,6 @@
 #include <crt_externs.h>
 #endif
 
-/* Make alloca work the best possible way.  */
-#ifdef __GNUC__
-# ifndef atarist
-#  ifndef alloca
-#   define alloca __builtin_alloca
-#  endif
-# endif	/* atarist */
-#else
-# ifdef HAVE_ALLOCA_H
-#  include <alloca.h>
-# else
-#  ifdef _AIX
-#pragma alloca
-#  else
-#   ifndef alloca		/* predefined by HP cc +Olibcalls */
-void *alloca();
-#   endif
-#  endif /* AIX */
-# endif	/* HAVE_ALLOCA_H */
-#endif /* __GNUC__ */
-
 #ifndef HAVE_STRING_H
 char *strrchr(const char *, const char);
 #endif
diff --git a/gc.c b/gc.c
index f5411282c8..b930621065 100644
--- a/gc.c
+++ b/gc.c
@@ -65,27 +65,6 @@
 #define rb_setjmp(env) RUBY_SETJMP(env)
 #define rb_jmp_buf rb_jmpbuf_t
 
-/* Make alloca work the best possible way.  */
-#ifdef __GNUC__
-# ifndef atarist
-#  ifndef alloca
-#   define alloca __builtin_alloca
-#  endif
-# endif /* atarist */
-#else
-# ifdef HAVE_ALLOCA_H
-#  include <alloca.h>
-# else
-#  ifdef _AIX
- #pragma alloca
-#  else
-#   ifndef alloca /* predefined by HP cc +Olibcalls */
-void *alloca ();
-#   endif
-#  endif /* AIX */
-# endif /* HAVE_ALLOCA_H */
-#endif /* __GNUC__ */
-
 #ifndef GC_MALLOC_LIMIT
 #define GC_MALLOC_LIMIT 8000000
 #endif
diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index e8f0d15380..d432f4b1f7 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -73,13 +73,26 @@ extern "C" {
 #pragma GCC visibility push(default)
 #endif
 
-#if defined(HAVE_ALLOCA_H)
-#include <alloca.h>
+/* Make alloca work the best possible way.  */
+#ifdef __GNUC__
+# ifndef atarist
+#  ifndef alloca
+#   define alloca __builtin_alloca
+#  endif
+# endif	/* atarist */
 #else
+# ifdef HAVE_ALLOCA_H
+#  include <alloca.h>
+# else
 #  ifdef _AIX
 #pragma alloca
-#  endif
-#endif
+#  else
+#   ifndef alloca		/* predefined by HP cc +Olibcalls */
+void *alloca();
+#   endif
+#  endif /* AIX */
+# endif	/* HAVE_ALLOCA_H */
+#endif /* __GNUC__ */
 
 #if defined HAVE_UINTPTR_T && 0
 typedef uintptr_t VALUE;