Merge branch 'copy_on_write' into caller_for_all_threads

FooBarWidget · Dec 30, 2011 · 57c90f2 · 57c90f2
2 parents 2e95d94 + 00b2e69
commit 57c90f2
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Showing 2 changed files with 41 additions and 2 deletions.
diff --git a/configure.in b/configure.in
@@ -154,7 +154,8 @@ if test $frame_address = yes; then
 fi
 AC_ARG_ENABLE(mbari-api,
        [  --enable-mbari-api      enable API changes from the MBARI patches. ],
-       [mbari_api=$enableval])
+       [mbari_api=$enableval],
+       [mbari_api=yes])
 if test "$mbari_api" = yes; then
     AC_DEFINE(MBARI_API)
 fi
@@ -620,6 +621,40 @@ powerpc-darwin*)
   ;;
 *)
   AC_FUNC_ALLOCA
+  if test $ac_cv_func_alloca_works = yes; then
+	# On Apple uses llvm-gcc since Xcode 4. llvm-gcc has this nice bug
+	# where __builtin_alloca(0) would return non-NULL with -O0, but NULL
+	# with -O2...
+	AC_CACHE_CHECK(whether alloca(0) returns the stack pointer, rb_cv_alloca_0_returns_stack_pointer,
+	  [AC_TRY_RUN([
+#ifdef HAVE_ALLOCA_H_
+#  include <alloca.h>
+#endif
+#include <stdlib.h>
+int
+main()
+{
+	/* It's important that we assign the result of alloca to a variable!
+	 * If we put it in the if-statement then the compiler's -O2 optimizations
+	 * will optimize it away to "if (true)", thereby bypassing our
+	 * llvm-gcc bug detection! Let's put 'volatile' in there too,
+	 * just in case.
+	 */
+	volatile void *addr = alloca(0);
+    if (addr != NULL) {
+        return 0;
+    } else {
+        return 1;
+    }
+}
+],
+		rb_cv_alloca_0_returns_stack_pointer=yes,
+		rb_cv_alloca_0_returns_stack_pointer=no,
+		rb_cv_alloca_0_returns_stack_pointer=no)])
+	if test $rb_cv_alloca_0_returns_stack_pointer = yes; then
+	  AC_DEFINE(ALLOCA_0_RETURNS_STACK_POINTER, 1)
+	fi
+  fi
   ;;
 esac
 AC_FUNC_MEMCMP

diff --git a/rubysig.h b/rubysig.h
@@ -234,7 +234,11 @@ __defspfn("mov %0, sp": "=r"(sp))
 #   warning No assembly version of __sp() defined for this CPU.
 #  endif
 # else
-#  define __sp()  ((VALUE *)__builtin_alloca(0))
+#  if ALLOCA_0_RETURNS_STACK_POINTER
+#    define __sp()  ((VALUE *)__builtin_alloca(0))
+#  else
+#    define __sp()  ((VALUE *)__builtin_alloca(sizeof(void *)))
+#  endif /* ALLOCA_0_RETURNS_STACK_POINTER */
 # endif
 
 #else  // not GNUC