mpi.h.in: Revamp MPI-1 removed function warnings

Refs #6278.

This commit is intended to be cherry-picked to v4.0.x and
the following commit will ammend to this functionality for
master's removal.

Changes the prototypes for MPI removed functions in the
following ways:

There are 4 cases:

 1) User wants MPI-1 compatibility (--enable-mpi1-compatibility)

    MPI_Address (and friends) are declared in mpi.h with
    deprecation notice

 2) User does not want MPI-1 compatibility, and has a C11-capable
    compiler

    Declare an MPI_Address (etc.) macro in mpi.h, which will
    cause a compile-time error using _Static_assert C11 feature

 3) User does not want MPI-1 compatibility, and does not have a
    C11-capable compiler, but the compiler supports error function
    attributes.

    Declare an MPI_Address (etc.) macro in mpi.h, which will
    cause a compile-time error using error function attribute.

 4) User does not want MPI-1 compatibility, and does not have a
    C11-capable compiler, or a compiler that supports error
    function attributes.

    Do not declare MPI_Address (etc.) in mpi.h at all.
    Unless the user is compiling with something like -Werror,
    this will allow the user's code to compile. We are
    choosing this because it seems like a losing battle to
    make some kind of compile time error that is friendly to
    the user (and doesn't make it look like mpi.h itself is broken).

    On v4.0.x, this will allow the user code to both compile
    (albeit with a warning) and link (because the MPI_Address
    will be in the MPI library because we are preserving ABI
    back to 3.0.x).

    On master/v5.0.x, this will allow the user code to compile,
    but it will fail to link (because the MPI_Address symbol will
    not be in the MPI library).

Signed-off-by: Geoffrey Paulsen <[email protected]>
(cherry-picked from 3136a17)

Author: gpaulsen

ompi/include/mpi.h.in

@@ -19,7 +19,8 @@
  * Copyright (c) 2015      University of Houston. All rights reserved.
  * Copyright (c) 2015-2018 Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
- * Copyright (c) 2017-2018 IBM Corporation.  All rights reserved.
+ * Copyright (c) 2017-2019 IBM Corporation.  All rights reserved.
+ * Copyright (c) 2018      FUJITSU LIMITED.  All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -279,10 +280,50 @@
 #                    define __mpi_interface_deprecated__(msg) __attribute__((__deprecated__))
 #                endif
 #            endif
-#            if (OMPI_ENABLE_MPI1_COMPAT && !OMPI_BUILDING)
-#                    define __mpi_interface_removed__(msg) __mpi_interface_deprecated__(msg)
-#                    define OMPI_OMIT_MPI1_COMPAT_DECLS 0
-#            endif
+#        endif
+
+         /* For MPI removed APIs, there is no generally portable way to cause
+          * the C compiler to error with a nice message, on the _usage_ of
+          * one of these symbols.  We've gone with tiered appraoch:
+          *
+          * If the user configured with --enable-mpi1-compatibility,
+          * just emit a compiletime warning (via the deprecation function
+          * attribute) that they're using an MPI1 removed function.
+          *
+          * Otherwise, we'd like to issue a fatal error directing the user
+          * that they've used an MPI1 removed function.  If the user's
+          * compiler supports C11 _Static_assert feature, we #define
+          * the MPI routines to instead be a call to _Static_assert
+          * with an appropreate message suggesting the new MPI3 equivalent.
+          *
+          * Otherwise, if the user's compiler supports the error function
+          * attribute, define the MPI routines with that error attribute.
+          * This is supported by most modern GNU compilers.
+          *
+          * Finally if the compiler doesn't support any of those, just
+          * Don't declare those MPI routines at all in mpi.h
+          *
+          * Don't do MACRO magic for building Profiling library as it
+          * interferes with the above.
+          */
+#        if (OMPI_ENABLE_MPI1_COMPAT || OMPI_BUILDING)
+#            define OMPI_OMIT_MPI1_COMPAT_DECLS 0
+#            define OMPI_REMOVED_USE_STATIC_ASSERT 0
+#            define __mpi_interface_removed__(func, newfunc) __mpi_interface_deprecated__(#func " was removed in MPI-3.0.  Use " #newfunc " instead.  continuing...")
+#        elif (__STDC_VERSION__ >= 201112L)
+#            define OMPI_OMIT_MPI1_COMPAT_DECLS 1
+#            define OMPI_REMOVED_USE_STATIC_ASSERT 1
+// This macro definition may show up in compiler output.  So we both
+// outdent it back to column 0 and give it a user-friendly name to
+// help users grok what we are trying to tell them here.
+#define THIS_SYMBOL_WAS_REMOVED_IN_MPI30(func, newfunc) _Static_assert(0, #func " was removed in MPI-3.0.  Use " #newfunc " instead.")
+#        elif OPAL_HAVE_ATTRIBUTE_ERROR
+#            define OMPI_OMIT_MPI1_COMPAT_DECLS 0
+#            define OMPI_REMOVED_USE_STATIC_ASSERT 0
+#            define __mpi_interface_removed__(func, newfunc) __attribute__((__error__(#func " was removed in MPI-3.0.  Use " #newfunc " instead.")))
+#        else
+#            define OMPI_OMIT_MPI1_COMPAT_DECLS 1
+#            define OMPI_REMOVED_USE_STATIC_ASSERT 0
 #        endif
 #    endif
 #endif
@@ -297,7 +338,15 @@
 #endif
 
 #if !defined(__mpi_interface_removed__)
-#    define __mpi_interface_removed__(msg)
+#    define __mpi_interface_removed__(A,B)
+#endif
+
+#if !defined(THIS_SYMBOL_WAS_REMOVED_IN_MPI30)
+#    define THIS_SYMBOL_WAS_REMOVED_IN_MPI30(func, newfunc)
+#endif
+
+#if !defined(OMPI_REMOVED_USE_STATIC_ASSERT)
+#    define OMPI_REMOVED_USE_STATIC_ASSERT 0
 #endif
 
 #if !defined(OMPI_OMIT_MPI1_COMPAT_DECLS)
@@ -1010,22 +1059,32 @@ OMPI_DECLSPEC extern struct ompi_predefined_info_t ompi_mpi_info_env;
 OMPI_DECLSPEC extern MPI_Fint *MPI_F_STATUS_IGNORE;
 OMPI_DECLSPEC extern MPI_Fint *MPI_F_STATUSES_IGNORE;
 
-#if (!OMPI_OMIT_MPI1_COMPAT_DECLS || OMPI_BUILDING)
 /*
  * Removed datatypes.  These datatypes are only available if Open MPI
  * was configured with --enable-mpi1-compatibility.
  *
  * These datatypes were formally removed from the MPI specification
  * and should no longer be used in MPI applications.
  */
-#define MPI_UB OMPI_PREDEFINED_GLOBAL(MPI_Datatype, ompi_mpi_ub)
-#define MPI_LB OMPI_PREDEFINED_GLOBAL(MPI_Datatype, ompi_mpi_lb)
+#if (OMPI_ENABLE_MPI1_COMPAT || OMPI_BUILDING)
+#    define MPI_UB OMPI_PREDEFINED_GLOBAL(MPI_Datatype, ompi_mpi_ub)
+#    define MPI_LB OMPI_PREDEFINED_GLOBAL(MPI_Datatype, ompi_mpi_lb)
+
+OMPI_DECLSPEC extern struct ompi_predefined_datatype_t ompi_mpi_lb;
+OMPI_DECLSPEC extern struct ompi_predefined_datatype_t ompi_mpi_ub;
+
+#else
+/* If not building or configured --enable-mpi1-compatibility, then
+ * we don't want these datatypes, instead we define MPI_UB and
+ * MPI_LB to our Static Assert message if the compiler supports
+ * that staticly assert with a nice message.
+ */
+#    if (OMPI_REMOVED_USE_STATIC_ASSERT)
+#        define MPI_UB THIS_SYMBOL_WAS_REMOVED_IN_MPI30(MPI_UB, MPI_Type_create_resized);
+#        define MPI_LB THIS_SYMBOL_WAS_REMOVED_IN_MPI30(MPI_LB, MPI_Type_create_resized);
+#    endif /* OMPI_REMOVED_USE_STATIC_ASSERT */
+#endif /* Removed datatypes */
 
-OMPI_DECLSPEC extern struct ompi_predefined_datatype_t ompi_mpi_lb
-            __mpi_interface_removed__("MPI_LB was removed in MPI-3.0; use MPI_Type_create_resized instead.");
-OMPI_DECLSPEC extern struct ompi_predefined_datatype_t ompi_mpi_ub
-            __mpi_interface_removed__("MPI_UB was removed in MPI-3.0; use MPI_Type_create_resized instead.");
-#endif /* !OMPI_OMIT_MPI1_COMPAT_DECLS */
 
 /*
  * MPI predefined handles
@@ -2695,61 +2754,74 @@ typedef void (MPI_Handler_function)(MPI_Comm *, int *, ...);
  * and should no longer be used in MPI applications.
  */
 OMPI_DECLSPEC  int MPI_Address(void *location, MPI_Aint *address)
-            __mpi_interface_removed__("MPI_Address was removed in MPI-3.0; use MPI_Get_address instead.");
+                   __mpi_interface_removed__(MPI_Address, MPI_Get_address);
 OMPI_DECLSPEC  int PMPI_Address(void *location, MPI_Aint *address)
-            __mpi_interface_removed__("PMPI_Address was removed in MPI-3.0; use MPI_Get_address instead.");
+                   __mpi_interface_removed__(PMPI_Address, PMPI_Get_address);
 OMPI_DECLSPEC  int MPI_Errhandler_create(MPI_Handler_function *function,
                                          MPI_Errhandler *errhandler)
-            __mpi_interface_removed__("MPI_Errhandler_create was removed in MPI-3.0; use MPI_Comm_create_errhandler instead.");
+                   __mpi_interface_removed__(MPI_Errhandler_create, MPI_Comm_create_errhandler);
 OMPI_DECLSPEC  int PMPI_Errhandler_create(MPI_Handler_function *function,
                                           MPI_Errhandler *errhandler)
-            __mpi_interface_removed__("PMPI_Errhandler_create was removed in MPI-3.0; use PMPI_Comm_create_errhandler instead.");
+                   __mpi_interface_removed__(PMPI_Errhandler_create, PMPI_Comm_create_errhandler);
 OMPI_DECLSPEC  int MPI_Errhandler_get(MPI_Comm comm, MPI_Errhandler *errhandler)
-            __mpi_interface_removed__("MPI_Errhandler_get was removed in MPI-3.0; use MPI_Comm_get_errhandler instead.");
+                   __mpi_interface_removed__(MPI_Errhandler_get, MPI_Comm_get_errhandler);
 OMPI_DECLSPEC  int PMPI_Errhandler_get(MPI_Comm comm, MPI_Errhandler *errhandler)
-            __mpi_interface_removed__("PMPI_Errhandler_get was removed in MPI-3.0; use PMPI_Comm_get_errhandler instead.");
+                   __mpi_interface_removed__(PMPI_Errhandler_get, PMPI_Comm_get_errhandler);
 OMPI_DECLSPEC  int MPI_Errhandler_set(MPI_Comm comm, MPI_Errhandler errhandler)
-            __mpi_interface_removed__("MPI_Errhandler_set was removed in MPI-3.0; use MPI_Comm_set_errhandler instead.");
+                   __mpi_interface_removed__(MPI_Errhandler_set, MPI_Comm_set_errhandler);
 OMPI_DECLSPEC  int PMPI_Errhandler_set(MPI_Comm comm, MPI_Errhandler errhandler)
-            __mpi_interface_removed__("PMPI_Errhandler_set was removed in MPI-3.0; use PMPI_Comm_set_errhandler instead.");
+                   __mpi_interface_removed__(PMPI_Errhandler_set, PMPI_Comm_set_errhandler);
 OMPI_DECLSPEC  int MPI_Type_extent(MPI_Datatype type, MPI_Aint *extent)
-            __mpi_interface_removed__("MPI_Type_extent was removed in MPI-3.0; use MPI_Type_get_extent instead.");
+                   __mpi_interface_removed__(MPI_Type_extent, MPI_Type_get_extent);
 OMPI_DECLSPEC  int PMPI_Type_extent(MPI_Datatype type, MPI_Aint *extent)
-            __mpi_interface_removed__("PMPI_Type_extent was removed in MPI-3.0; use PMPI_Type_get_extent instead.");
+                   __mpi_interface_removed__(PMPI_Type_extent, PMPI_Type_get_extent);
 OMPI_DECLSPEC  int MPI_Type_hindexed(int count, int array_of_blocklengths[],
                                      MPI_Aint array_of_displacements[],
                                      MPI_Datatype oldtype, MPI_Datatype *newtype)
-            __mpi_interface_removed__("MPI_Type_hindexed was removed in MPI-3.0; use MPI_Type_create_hindexed instead.");
+                   __mpi_interface_removed__(MPI_Type_hindexed, MPI_Type_create_hindexed);
 OMPI_DECLSPEC  int PMPI_Type_hindexed(int count, int array_of_blocklengths[],
                                       MPI_Aint array_of_displacements[],
                                       MPI_Datatype oldtype, MPI_Datatype *newtype)
-            __mpi_interface_removed__("PMPI_Type_hindexed was removed in MPI-3.0; use PMPI_Type_create_hindexed instead.");
+                   __mpi_interface_removed__(PMPI_Type_hindexed, PMPI_Type_create_hindexed);
 OMPI_DECLSPEC  int MPI_Type_hvector(int count, int blocklength, MPI_Aint stride,
                                     MPI_Datatype oldtype, MPI_Datatype *newtype)
-            __mpi_interface_removed__("MPI_Type_hvector was removed in MPI-3.0; use MPI_Type_create_hvector instead.");
+                   __mpi_interface_removed__(MPI_Type_hvector, MPI_Type_create_hvector);
 OMPI_DECLSPEC  int PMPI_Type_hvector(int count, int blocklength, MPI_Aint stride,
                                      MPI_Datatype oldtype, MPI_Datatype *newtype)
-            __mpi_interface_removed__("PMPI_Type_hvector was removed in MPI-3.0; use PMPI_Type_create_hvector instead.");
+                   __mpi_interface_removed__(PMPI_Type_hvector, PMPI_Type_create_hvector);
 OMPI_DECLSPEC  int MPI_Type_lb(MPI_Datatype type, MPI_Aint *lb)
-            __mpi_interface_removed__("MPI_Type_lb has been removed in MPI-3.0; use MPI_Type_get_extent instead.");
+                   __mpi_interface_removed__(MPI_Type_lb, MPI_Type_get_extent);
 OMPI_DECLSPEC  int PMPI_Type_lb(MPI_Datatype type, MPI_Aint *lb)
-            __mpi_interface_removed__("PMPI_Type_lb has been removed in MPI-3.0; use PMPI_Type_get_extent instead.");
+                   __mpi_interface_removed__(PMPI_Type_lb, PMPI_Type_get_extent);
 OMPI_DECLSPEC  int MPI_Type_struct(int count, int array_of_blocklengths[],
                                    MPI_Aint array_of_displacements[],
                                    MPI_Datatype array_of_types[],
                                    MPI_Datatype *newtype)
-            __mpi_interface_removed__("MPI_Type_struct was removed in MPI-3.0; use MPI_Type_create_struct instead.");
+                   __mpi_interface_removed__(MPI_Type_struct, MPI_Type_create_struct);
 OMPI_DECLSPEC  int PMPI_Type_struct(int count, int array_of_blocklengths[],
                                     MPI_Aint array_of_displacements[],
                                     MPI_Datatype array_of_types[],
                                     MPI_Datatype *newtype)
-            __mpi_interface_removed__("PMPI_Type_struct was removed in MPI-3.0; use PMPI_Type_create_struct instead.");
+                   __mpi_interface_removed__(PMPI_Type_struct, PMPI_Type_create_struct);
 OMPI_DECLSPEC  int MPI_Type_ub(MPI_Datatype mtype, MPI_Aint *ub)
-            __mpi_interface_removed__("MPI_Type_ub has been removed in MPI-3.0; use MPI_Type_get_extent instead.");
+                   __mpi_interface_removed__(MPI_Type_ub, MPI_Type_get_extent);
 OMPI_DECLSPEC  int PMPI_Type_ub(MPI_Datatype mtype, MPI_Aint *ub)
-            __mpi_interface_removed__("PMPI_Type_ub has been removed in MPI-3.0; use PMPI_Type_get_extent instead.");
+                   __mpi_interface_removed__(PMPI_Type_ub, PMPI_Type_get_extent);
 #endif /* !OMPI_OMIT_MPI1_COMPAT_DECLS */
 
+#if OMPI_REMOVED_USE_STATIC_ASSERT
+#define MPI_Address(...)  THIS_SYMBOL_WAS_REMOVED_IN_MPI30(MPI_Address, MPI_Get_address)
+#define MPI_Errhandler_create(...)  THIS_SYMBOL_WAS_REMOVED_IN_MPI30(MPI_Errhandler_create, MPI_Comm_create_errhandler)
+#define MPI_Errhandler_get(...)  THIS_SYMBOL_WAS_REMOVED_IN_MPI30(MPI_Errhandler_get, MPI_Comm_get_errhandler)
+#define MPI_Errhandler_set(...)  THIS_SYMBOL_WAS_REMOVED_IN_MPI30(MPI_Errhandler_set, MPI_Comm_set_errhandler)
+#define MPI_Type_extent(...)  THIS_SYMBOL_WAS_REMOVED_IN_MPI30(MPI_Type_extent, MPI_Type_get_extent)
+#define MPI_Type_hindexed(...)  THIS_SYMBOL_WAS_REMOVED_IN_MPI30(MPI_Type_hindexed, MPI_Type_create_hindexed)
+#define MPI_Type_hvector(...)  THIS_SYMBOL_WAS_REMOVED_IN_MPI30(MPI_Type_hvector, MPI_Type_create_hvector)
+#define MPI_Type_lb(...)  THIS_SYMBOL_WAS_REMOVED_IN_MPI30(MPI_Type_lb, MPI_Type_get_extent)
+#define MPI_Type_struct(...)  THIS_SYMBOL_WAS_REMOVED_IN_MPI30(MPI_Type_struct, MPI_Type_create_struct)
+#define MPI_Type_ub(...)  THIS_SYMBOL_WAS_REMOVED_IN_MPI30(MPI_Type_ub, MPI_Type_get_extent)
+#endif
+
 #if defined(c_plusplus) || defined(__cplusplus)
 }
 #endif

ompi/mpi/c/address.c

@@ -11,6 +11,7 @@
  *                         All rights reserved.
  * Copyright (c) 2015      Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
+ * Copyright (c) 2019      IBM Corporation.  All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -21,16 +22,11 @@
 #include "ompi_config.h"
 #include <stdio.h>
 
-/* This implementation has been removed from the MPI 3.1 standard.
+/* This implementation has been removed from the MPI 3.0 standard.
  * Open MPI v4.0.x is keeping the implementation in the library, but
  * removing the prototypes from the headers, unless the user configures
  * with --enable-mpi1-compatibility.
- *
- * To prevent having to port these implementations of removed functions
- * to the newer MPI calls, we are defining ENABLE_MPI1_COMPAT to 1
- * before including the c bindings.
  */
-#define ENABLE_MPI1_COMPAT 1
 
 #include "ompi/mpi/c/bindings.h"
 #include "ompi/runtime/params.h"
@@ -41,6 +37,10 @@
 #if OPAL_HAVE_WEAK_SYMBOLS
 #pragma weak MPI_Address = PMPI_Address
 #endif
+/* undef before defining, to prevent possible redefinition when
+ * using _Static_assert to error on usage of removed functions.
+ */
+#undef MPI_Address
 #define MPI_Address PMPI_Address
 #endif
 

ompi/mpi/c/errhandler_create.c

@@ -11,6 +11,7 @@
  *                         All rights reserved.
  * Copyright (c) 2015      Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
+ * Copyright (c) 2019      IBM Corporation.  All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -20,9 +21,11 @@
 
 #include "ompi_config.h"
 
-/* defining ENABLE_MPI1_COMPAT to 1 for removed implementations here.
- * see comments in address.c for more information. */
-#define ENABLE_MPI1_COMPAT 1
+/* This implementation has been removed from the MPI 3.0 standard.
+ * Open MPI v4.0.x is keeping the implementation in the library, but
+ * removing the prototypes from the headers, unless the user configures
+ * with --enable-mpi1-compatibility.
+ */
 
 #include "ompi/mpi/c/bindings.h"
 #include "ompi/communicator/communicator.h"
@@ -32,6 +35,10 @@
 #if OPAL_HAVE_WEAK_SYMBOLS
 #pragma weak MPI_Errhandler_create = PMPI_Errhandler_create
 #endif
+/* undef before defining, to prevent possible redefinition when
+ * using _Static_assert to error on usage of removed functions.
+ */
+#undef MPI_Errhandler_create
 #define MPI_Errhandler_create PMPI_Errhandler_create
 #endif
 

ompi/mpi/c/errhandler_get.c

@@ -11,6 +11,7 @@
  *                         All rights reserved.
  * Copyright (c) 2015      Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
+ * Copyright (c) 2019      IBM Corporation.  All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -20,9 +21,11 @@
 
 #include "ompi_config.h"
 
-/* defining ENABLE_MPI1_COMPAT to 1 for removed implementations here.
- * see comments in address.c for more information. */
-#define ENABLE_MPI1_COMPAT 1
+/* This implementation has been removed from the MPI 3.0 standard.
+ * Open MPI v4.0.x is keeping the implementation in the library, but
+ * removing the prototypes from the headers, unless the user configures
+ * with --enable-mpi1-compatibility.
+ */
 
 #include "ompi/mpi/c/bindings.h"
 #include "ompi/runtime/params.h"
@@ -34,6 +37,10 @@
 #if OPAL_HAVE_WEAK_SYMBOLS
 #pragma weak MPI_Errhandler_get = PMPI_Errhandler_get
 #endif
+/* undef before defining, to prevent possible redefinition when
+ * using _Static_assert to error on usage of removed functions.
+ */
+#undef MPI_Errhandler_get
 #define MPI_Errhandler_get PMPI_Errhandler_get
 #endif
 

ompi/mpi/c/errhandler_set.c

@@ -11,6 +11,7 @@
  *                         All rights reserved.
  * Copyright (c) 2015      Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
+ * Copyright (c) 2019      IBM Corporation.  All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -20,9 +21,11 @@
 
 #include "ompi_config.h"
 
-/* defining ENABLE_MPI1_COMPAT to 1 for removed implementations here.
- * see comments in address.c for more information. */
-#define ENABLE_MPI1_COMPAT 1
+/* This implementation has been removed from the MPI 3.0 standard.
+ * Open MPI v4.0.x is keeping the implementation in the library, but
+ * removing the prototypes from the headers, unless the user configures
+ * with --enable-mpi1-compatibility.
+ */
 
 #include "ompi/mpi/c/bindings.h"
 #include "ompi/runtime/params.h"
@@ -34,6 +37,10 @@
 #if OPAL_HAVE_WEAK_SYMBOLS
 #pragma weak MPI_Errhandler_set = PMPI_Errhandler_set
 #endif
+/* undef before defining, to prevent possible redefinition when
+ * using _Static_assert to error on usage of removed functions.
+ */
+#undef MPI_Errhandler_set
 #define MPI_Errhandler_set PMPI_Errhandler_set
 #endif
 

ompi/mpi/c/type_extent.c

@@ -11,6 +11,7 @@
  *                         All rights reserved.
  * Copyright (c) 2015      Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
+ * Copyright (c) 2019      IBM Corporation.  All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -20,9 +21,11 @@
 
 #include "ompi_config.h"
 
-/* defining ENABLE_MPI1_COMPAT to 1 for removed implementations here.
- * see comments in address.c for more information. */
-#define ENABLE_MPI1_COMPAT 1
+/* This implementation has been removed from the MPI 3.0 standard.
+ * Open MPI v4.0.x is keeping the implementation in the library, but
+ * removing the prototypes from the headers, unless the user configures
+ * with --enable-mpi1-compatibility.
+ */
 
 #include "ompi/mpi/c/bindings.h"
 #include "ompi/runtime/params.h"
@@ -35,6 +38,10 @@
 #if OPAL_HAVE_WEAK_SYMBOLS
 #pragma weak MPI_Type_extent = PMPI_Type_extent
 #endif
+/* undef before defining, to prevent possible redefinition when
+ * using _Static_assert to error on usage of removed functions.
+ */
+#undef MPI_Type_extent
 #define MPI_Type_extent PMPI_Type_extent
 #endif