diff --git a/config/ompi_setup_cc.m4 b/config/ompi_setup_cc.m4
index 40340fc7a7..cace63c866 100644
--- a/config/ompi_setup_cc.m4
+++ b/config/ompi_setup_cc.m4
@@ -37,10 +37,6 @@ BASECC="`basename $CC`"
 CFLAGS="$ompi_cflags_save"
 AC_DEFINE_UNQUOTED(OMPI_CC, "$CC", [OMPI underlying C compiler])
 
-# When building OMPI, we need this everywhere
-
-CPPFLAGS="$CPPFLAGS -DOMPI_BUILDING=1"
-
 # Check for compilers that impersonate gcc
 
 AC_MSG_CHECKING([for compilers that impersonate gcc])
diff --git a/configure.ac b/configure.ac
index 83c67e05d8..acf5a1376c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1176,11 +1176,7 @@ AC_DEFINE_UNQUOTED(ompi_fortran_dblprec_t, $MPI_FORTRAN_DBLPREC_TYPE,
 MPI_OFFSET_TYPE="not found"
 MPI_OFFSET_DATATYPE="not found"
 AC_MSG_CHECKING([checking for type of MPI_Offset])
-if test "$ac_cv_type_int64_t" = "yes"; then
-	MPI_OFFSET_TYPE=int64_t
-        # Need to figure out MPI_OFFSET_DATATYPE below
-        MPI_OFFSET_SIZE=8
-elif test "$ac_cv_type_long_long" = "yes" -a "$ac_cv_sizeof_long_long" = 8; then
+if test "$ac_cv_type_long_long" = "yes" -a "$ac_cv_sizeof_long_long" = 8; then
 	MPI_OFFSET_TYPE="long long"
         MPI_OFFSET_DATATYPE=MPI_LONG_LONG
         MPI_OFFSET_SIZE=8
@@ -1192,10 +1188,6 @@ elif test "ac_cv_sizeof_int" = 8; then
 	MPI_OFFSET_TYPE=int
         MPI_OFFSET_DATATYPE=MPI_INT
         MPI_OFFSET_SIZE=8
-elif test "$ac_cv_type_int32_t" = "yes"; then
-	MPI_OFFSET_TYPE=int32_t
-        # Need to figure out MPI_OFFSET_DATATYPE below
-        MPI_OFFSET_SIZE=4
 elif test "$ac_cv_type_long_long" = "yes" -a "$ac_cv_sizeof_long_long" = 4; then
 	MPI_OFFSET_TYPE="long long"
         MPI_OFFSET_DATATYPE=MPI_LONG_LONG
@@ -1218,30 +1210,9 @@ AC_DEFINE_UNQUOTED(MPI_Offset, $MPI_OFFSET_TYPE, [Type of MPI_Offset])
 
 #
 # If we haven't already, figure out an MPI datatype that corresponds
-# to the back-end C type of MPI_Offset.  We'll only not have figured
-# this out already if the type of MPI_Offset is int32_t or int64_t.
+# to the back-end C type of MPI_Offset.
 #
-
 AC_MSG_CHECKING([checking for an MPI datatype for MPI_Offset])
-if test "$MPI_OFFSET_DATATYPE" = "not found"; then
-    if test "$MPI_OFFSET_TYPE" = "int64_t"; then
-        if test "$ac_cv_type_long_long" = "yes" -a "$ac_cv_sizeof_long_long" = 8; then
-            MPI_OFFSET_DATATYPE=MPI_LONG_LONG
-        elif test "$ac_cv_type_long" = "yes" -a "$ac_cv_sizeof_long" = 8; then
-            MPI_OFFSET_DATATYPE=MPI_LONG
-        elif test "ac_cv_sizeof_int" = 8; then
-            MPI_OFFSET_DATATYPE=MPI_INT
-        fi
-    elif test "$MPI_OFFSET_TYPE" = "int32_t"; then
-        if test "$ac_cv_type_long_long" = "yes" -a "$ac_cv_sizeof_long_long" = 4; then
-            MPI_OFFSET_DATATYPE=MPI_LONG_LONG
-        elif test "$ac_cv_type_long" = "yes" -a "$ac_cv_sizeof_long" = 4; then
-            MPI_OFFSET_DATATYPE=MPI_LONG
-        elif test "ac_cv_sizeof_int" = 4; then
-            MPI_OFFSET_DATATYPE=MPI_INT
-        fi
-    fi
-fi
 AC_MSG_RESULT([$MPI_OFFSET_DATATYPE])
 if test "$MPI_OFFSET_DATATYPE" = "not found"; then
 	AC_MSG_WARN([*** Unable to find an MPI datatype corresponding to MPI_Offset])
diff --git a/include/mpi.h b/include/mpi.h
index 8f67fe157f..36bda981d2 100644
--- a/include/mpi.h
+++ b/include/mpi.h
@@ -17,6 +17,16 @@
 #ifndef OMPI_MPI_H
 #define OMPI_MPI_H
 
+/*
+ * Turn off OMPI_BUILDING if we were included before ompi_config.h,
+ * which should happen whenever an MPI application is involved.  This
+ * will turn off most of the includes / compatibility code in
+ * ompi_config_bottom.h, giving the user an expected experience.
+ */
+#ifndef OMPI_BUILDING
+#define OMPI_BUILDING 0
+#endif
+
 #include "ompi_config.h"
 
 /*
@@ -34,7 +44,7 @@
  * To accomodate programs written for MPI implementations that use a
  * straight ROMIO import
  */
-#if !defined(OMPI_BUILDING) || !OMPI_BUILDING
+#if !OMPI_BUILDING
 #define MPIO_Request MPI_Request
 #define MPIO_Test MPI_Test
 #define MPIO_Wait MPI_Wait
@@ -1636,12 +1646,10 @@ OMPI_DECLSPEC  double PMPI_Wtime(void);
  *   - We are using a C++ compiler
  */
 
-#if defined(OMPI_WANT_CXX_BINDINGS)
-#if !defined(OMPI_BUILDING) || !OMPI_BUILDING
+#if defined(OMPI_WANT_CXX_BINDINGS) && !OMPI_BUILDING
 #if defined(__cplusplus) || defined(c_plusplus) 
 #include "mpi/cxx/mpicxx.h"
 #endif
 #endif
-#endif
 
 #endif /* OMPI_MPI_H */
diff --git a/include/ompi_config_bottom.h b/include/ompi_config_bottom.h
index 732246de70..0143ef261d 100644
--- a/include/ompi_config_bottom.h
+++ b/include/ompi_config_bottom.h
@@ -22,42 +22,82 @@
  * need to #ifndef/#endif protection here.
  */
 
-#ifndef OMPI_CONFIG_BOTTOM_H 
-#define OMPI_CONFIG_BOTTOM_H
- 
-#if defined(WIN32) && defined(OMPI_BUILDING) && OMPI_BUILDING
-#include "win32/win_compat.h"
-#define OMPI_COMP_EXPORT __declspec(dllexport)
+#ifndef OMPI_CONFIG_H 
+#error "ompi_config_bottom.h should only be included from ompi_config.h"
 #endif
 
-#if defined(WIN32) 
-#    if defined(OMPI_BUILDING)
-#        if OMPI_BUILDING
-#            define OMPI_DECLSPEC __declspec(dllexport)
-#        else
-#            define OMPI_DECLSPEC __declspec(dllimport)
-#        endif
-#   endif
-#   ifndef OMPI_DECLSPEC 
-    /* this is for the applications. here WIN32 is defined, but no OMPI_BUILDING */
-#       define OMPI_DECLSPEC __declspec(dllimport)
-#   endif
+/*
+ * OMPI_BUILDING will be true whenever ompi_config.h is included in a
+ * file that is "internal" to Open MPI, meaning something that is
+ * below the MPI layer.  It will be false whenever we should provide
+ * the most "untampered" environment possible.  The user is free to
+ * override this before including either mpi.h or ompi_config.h, if so
+ * desired.
+ */
+#ifndef OMPI_BUILDING
+#define OMPI_BUILDING 1
 #endif
 
-#ifndef OMPI_DECLSPEC 
-#define OMPI_DECLSPEC
+/***********************************************************************
+ *
+ * code that should be in ompi_config_bottom.h regardless of build
+ * status
+ *
+ **********************************************************************/
+
+/* Do we have thread support? */
+#define OMPI_HAVE_THREAD_SUPPORT (OMPI_ENABLE_MPI_THREADS || OMPI_ENABLE_PROGRESS_THREADS)
+
+/* * C type for Fortran COMPLEX */
+typedef struct {
+  ompi_fortran_real_t real;
+  ompi_fortran_real_t imag;
+} ompi_fortran_complex_t;
+
+
+/* * C type for Fortran DOUBLE COMPLEX */
+typedef struct {
+  ompi_fortran_dblprec_t real;
+  ompi_fortran_dblprec_t imag;
+} ompi_fortran_dblcomplex_t;
+
+
+/***********************************************************************
+ *
+ * Windows library interface declaration code
+ *
+ **********************************************************************/
+
+#if defined(WIN32)
+#  if OMPI_BUILDING
+#    include "win32/win_compat.h"
+#    define OMPI_COMP_EXPORT __declspec(dllexport)
+#    define OMPI_DECLSPEC __declspec(dllexport)
+#  else
+#    define OMPI_COMP_EXPORT
+#    define OMPI_DECLSPEC __declspec(dllimport)
+#  endif
+#else
+#  define OMPI_COMP_EXPORT
+#  define OMPI_DECLSPEC
 #endif
 
-#ifndef OMPI_COMP_EXPORT
-#define OMPI_COMP_EXPORT
-#endif
+
+/***********************************************************************
+ *
+ * Code that is only for when building Open MPI or utilities that are
+ * using the internals of Open MPI.  It should not be included when
+ * building MPI applicatiosn
+ *
+ **********************************************************************/
+#if OMPI_BUILDING
 
 /*
  * If we're in C, we may need to bring in the bool type and true/false
  * constants.  OMPI_NEED_C_BOOL will be true if the compiler either
  * needs <stdbool.h> or doesn't define the bool type at all.
  */
-#if !defined(__cplusplus) && defined(OMPI_BUILDING)
+#if !defined(__cplusplus)
 #    if OMPI_NEED_C_BOOL
 #        if OMPI_USE_STDBOOL_H
              /* If we're using <stdbool.h>, there is an implicit
@@ -103,11 +143,6 @@ typedef long long bool;
 #define OMPI_PATH_MAX	256
 #endif
 
-/*
- * Do we have thread support?
- */
-#define OMPI_HAVE_THREAD_SUPPORT (OMPI_ENABLE_MPI_THREADS || OMPI_ENABLE_PROGRESS_THREADS)
-
 /*
  * Do we have <stdint.h>?
  */
@@ -135,10 +170,10 @@ typedef long long bool;
  * So for 1, everyone must include <ompi_config.h> first.  For 2, the
  * C++ bindings will never include <ompi_config.h> -- they will only
  * include <mpi.h>, which includes <ompi_config.h>, but after
- * OMPI_MPI_H is defined.  For 3, it's the same as 1 -- just include
+ * setting OMPI_BUILDING to 0  For 3, it's the same as 1 -- just include
  * <ompi_config.h> first.
  */
-#if OMPI_ENABLE_MEM_DEBUG && defined(OMPI_BUILDING) && OMPI_BUILDING && !defined(OMPI_MPI_H)
+#if OMPI_ENABLE_MEM_DEBUG
 
 /* It is safe to include util/malloc.h here because a) it will only
    happen when we are building OMPI and therefore have a full OMPI
@@ -173,29 +208,10 @@ typedef long long bool;
 #endif
 
 
-/*
- * C type for Fortran COMPLEX
- */
-typedef struct {
-  ompi_fortran_real_t real;
-  ompi_fortran_real_t imag;
-} ompi_fortran_complex_t;
-
-
-/*
- * C type for Fortran DOUBLE COMPLEX
- */
-typedef struct {
-  ompi_fortran_dblprec_t real;
-  ompi_fortran_dblprec_t imag;
-} ompi_fortran_dblcomplex_t;
-
 
 /*
  * printf functions for portability (only when building Open MPI)
  */
-
-#if defined(OMPI_BUILDING) && OMPI_BUILDING
 #if !defined(HAVE_VASPRINTF) || !defined(HAVE_VSNPRINTF)
 #include <stdarg.h>
 #include <stdlib.h>
@@ -220,7 +236,6 @@ typedef struct {
 #ifndef HAVE_VSNPRINTF
 # define vsnprintf ompi_vsnprintf
 #endif
-#endif
 
 /*
  * Define __func__-preprocessor directive if the compiler does not
@@ -229,9 +244,8 @@ typedef struct {
  * coming from (assuming that __func__ is typically used for
  * printf-style debugging).
  */
-
-#if defined(OMPI_BUILDING) && OMPI_BUILDING && defined(HAVE_DECL___FUNC__) && !HAVE_DECL___FUNC__
+#if defined(HAVE_DECL___FUNC__) && !HAVE_DECL___FUNC__
 #define __func__ __FILE__
 #endif
 
-#endif /* OMPI_CONFIG_BOTTOM_H */
+#endif /* OMPI_BUILDING */
diff --git a/src/mca/io/romio/romio-dist/adio/common/Makefile.am b/src/mca/io/romio/romio-dist/adio/common/Makefile.am
index 6254cfb8a6..0f6a74e03b 100644
--- a/src/mca/io/romio/romio-dist/adio/common/Makefile.am
+++ b/src/mca/io/romio/romio-dist/adio/common/Makefile.am
@@ -17,6 +17,7 @@
 include $(top_ompi_srcdir)/config/Makefile.options
 
 AM_CPPFLAGS = \
+        -DOMPI_BUILDING=1 \
         -I$(top_ompi_builddir)/include \
         -I$(top_ompi_srcdir)/src \
         -I$(top_ompi_srcdir)/src/include \
diff --git a/test/asm/atomic_barrier.c b/test/asm/atomic_barrier.c
index 47bdd16807..9c8f656f31 100644
--- a/test/asm/atomic_barrier.c
+++ b/test/asm/atomic_barrier.c
@@ -14,7 +14,7 @@
  * $HEADER$
  */
 
-#undef OMPI_BUILDING
+#define OMPI_BUILDING 0
 #include "ompi_config.h"
 
 #include "include/sys/atomic.h"
diff --git a/test/asm/atomic_cmpset.c b/test/asm/atomic_cmpset.c
index b684c067fc..6ee851cb65 100644
--- a/test/asm/atomic_cmpset.c
+++ b/test/asm/atomic_cmpset.c
@@ -14,7 +14,7 @@
  * $HEADER$
  */
 
-#undef OMPI_BUILDING
+#define OMPI_BUILDING 0
 #include "ompi_config.h"
 
 #undef NDEBUG
diff --git a/test/asm/atomic_math.c b/test/asm/atomic_math.c
index fffb63917a..aadd555b49 100644
--- a/test/asm/atomic_math.c
+++ b/test/asm/atomic_math.c
@@ -14,7 +14,7 @@
  * $HEADER$
  */
 
-#undef OMPI_BUILDING
+#define OMPI_BUILDING 0
 #include "ompi_config.h"
 
 #ifdef HAVE_PTHREAD_H
diff --git a/test/asm/atomic_spinlock.c b/test/asm/atomic_spinlock.c
index 00ccff9be3..2754e09b8b 100644
--- a/test/asm/atomic_spinlock.c
+++ b/test/asm/atomic_spinlock.c
@@ -14,7 +14,7 @@
  * $HEADER$
  */
 
-#undef OMPI_BUILDING
+#define OMPI_BUILDING 0
 #include "ompi_config.h"
 
 #ifdef HAVE_PTHREAD_H