Merge pull request #12660 from devreal/require-c11

Require C11

Author: bosilca

config/opal_setup_cc.m4

@@ -170,7 +170,7 @@ AC_DEFUN([OPAL_SETUP_CC],[
     AC_REQUIRE([_OPAL_PROG_CC])
     AC_REQUIRE([AM_PROG_CC_C_O])
 
-    OPAL_VAR_SCOPE_PUSH([opal_prog_cc_c11_helper__Thread_local_available opal_prog_cc_c11_helper_atomic_var_available opal_prog_cc_c11_helper__Atomic_available opal_prog_cc_c11_helper__static_assert_available opal_prog_cc_c11_helper__Generic_available opal_prog_cc__thread_available opal_prog_cc_c11_helper_atomic_fetch_xor_explicit_available opal_prog_cc_c11_helper_proper__Atomic_support_in_atomics])
+    OPAL_VAR_SCOPE_PUSH([opal_prog_cc_c11_helper__Thread_local_available opal_prog_cc_c11_helper_atomic_var_available opal_prog_cc_c11_helper__Atomic_available opal_prog_cc_c11_helper__static_assert_available opal_prog_cc_c11_helper__Generic_available opal_prog_cc_c11_helper_atomic_fetch_xor_explicit_available opal_prog_cc_c11_helper_proper__Atomic_support_in_atomics])
 
     OPAL_PROG_CC_C11
 
@@ -179,33 +179,11 @@ AC_DEFUN([OPAL_SETUP_CC],[
     OPAL_C_COMPILER_VENDOR([opal_c_vendor])
 
     if test $opal_cv_c11_supported = no ; then
-        # It is not currently an error if C11 support is not available. Uncomment the
-        # following lines and update the warning when we require a C11 compiler.
-        # AC_MSG_WARNING([Open MPI requires a C11 (or newer) compiler])
-        # AC_MSG_ERROR([Aborting.])
-        # From Open MPI 1.7 on we require a C99 compliant compiler
-        dnl with autoconf 2.70 AC_PROG_CC makes AC_PROG_CC_C99 obsolete
-        m4_version_prereq([2.70],
-            [],
-            [AC_PROG_CC_C99])
-        # The result of AC_PROG_CC_C99 is stored in ac_cv_prog_cc_c99
-        if test "x$ac_cv_prog_cc_c99" = xno ; then
-            AC_MSG_WARN([Open MPI requires a C99 (or newer) compiler. C11 is recommended.])
-            AC_MSG_ERROR([Aborting.])
-        fi
-
-        # Get the correct result for C11 support flags now that the compiler flags have
-        # changed
-        OPAL_PROG_CC_C11_HELPER([], [], [])
+        # C11 is required
+        AC_MSG_WARN([Open MPI requires a C11 (or newer) compiler. C11 is required.])
+        AC_MSG_ERROR([Aborting.])
     fi
 
-    # Check if compiler support __thread
-    OPAL_CC_HELPER([if $CC $1 supports __thread], [opal_prog_cc__thread_available],
-               [],[[static __thread int  foo = 1;++foo;]])
-
-    OPAL_CC_HELPER([if $CC $1 supports C11 _Thread_local], [opal_prog_cc_c11_helper__Thread_local_available],
-                   [],[[static _Thread_local int  foo = 1;++foo;]])
-
     dnl At this time Open MPI only needs thread local and the atomic convenience types for C11 support. These
     dnl will likely be required in the future.
     AC_DEFINE_UNQUOTED([OPAL_C_HAVE__THREAD_LOCAL], [$opal_prog_cc_c11_helper__Thread_local_available],
@@ -223,9 +201,6 @@ AC_DEFUN([OPAL_SETUP_CC],[
     AC_DEFINE_UNQUOTED([OPAL_C_HAVE__STATIC_ASSERT], [$opal_prog_cc_c11_helper__static_assert_available],
                        [Whether C compiler support _Static_assert keyword])
 
-    AC_DEFINE_UNQUOTED([OPAL_C_HAVE___THREAD], [$opal_prog_cc__thread_available],
-                       [Whether C compiler supports __thread])
-
     # Check for standard headers, needed here because needed before
     # the types checks.  This is only necessary for Autoconf < v2.70.
     m4_version_prereq([2.70],

docs/developers/prerequisites.rst

@@ -5,7 +5,7 @@ Compilers
 ---------
 
 Although it should probably be assumed, you'll need a C compiler that
-supports C99.
+supports C11.
 
 You'll also need a Fortran compiler if you want to build the Fortran
 MPI bindings (the more recent the Fortran compiler, the better), and a

docs/developers/source-code.rst

@@ -47,7 +47,7 @@ C / C++
      if (whatever)
         return OMPI_SUCCESS;
 
-* Starting with Open MPI 1.7, Open MPI requires a C99-compliant
+* Starting with Open MPI 6.0, Open MPI requires a C11-compliant
   compiler.
 
   * C++-style comments are now allowed (and preferred).

docs/release-notes/changelog/index.rst

@@ -8,6 +8,7 @@ since v1.0.0.
 .. toctree::
    :maxdepth: 1
 
+   v6.0.x
    v5.0.x
    v4.1.x
    v4.0.x

docs/release-notes/changelog/v6.0.x.rst

@@ -0,0 +1,11 @@
+Open MPI v6.0.x series
+======================
+
+This file contains all the NEWS updates for the Open MPI v6.0.x
+series, in reverse chronological order.
+
+Open MPI version v6.0.0
+--------------------------
+:Date: ...fill me in...
+
+- Open MPI now requires a C11-compliant compiler to build.

docs/release-notes/compilers.rst

@@ -3,7 +3,7 @@
 Compiler Notes
 ==============
 
-* Open MPI requires a C99-capable compiler to build.
+* Open MPI requires a C11-capable compiler to build.
 
 * On platforms other than x86-64, AArc64 (64-bit ARM), and PPC, Open
   MPI requires a compiler that either supports C11 atomics or the GCC

ompi/mca/vprotocol/pessimist/vprotocol_pessimist_wait.c

@@ -20,7 +20,7 @@ static int vprotocol_pessimist_request_no_free(ompi_request_t **req) {
 }
 
 #define PREPARE_REQUESTS_WITH_NO_FREE(count, requests) do { \
-    for (typeof(count) i = 0; i < count; i++)     \
+    for (size_t i = 0; i < count; i++)     \
     { \
         if(requests[i] == MPI_REQUEST_NULL) continue; \
         requests[i]->req_free = vprotocol_pessimist_request_no_free; \

opal/class/opal_fifo.h

@@ -224,7 +224,7 @@ static inline opal_list_item_t *opal_fifo_pop_atomic(opal_fifo_t *fifo)
         if (++attempt == 5) {
             /* deliberately suspend this thread to allow other threads to run. this should
              * only occur during periods of contention on the lifo. */
-            _opal_lifo_release_cpu();
+            opal_lifo_release_cpu();
             attempt = 0;
         }
 

opal/class/opal_lifo.c

@@ -19,7 +19,11 @@
  * $HEADER$
  */
 
+/* needed for nanosleep() */
+#define _POSIX_C_SOURCE 200809L
+
 #include "opal_config.h"
+#include <time.h>
 #include "opal/class/opal_lifo.h"
 
 static void opal_lifo_construct(opal_lifo_t *lifo)
@@ -31,3 +35,16 @@ static void opal_lifo_construct(opal_lifo_t *lifo)
 }
 
 OBJ_CLASS_INSTANCE(opal_lifo_t, opal_object_t, opal_lifo_construct, NULL);
+
+
+void opal_lifo_release_cpu(void)
+{
+    /* NTH: there are many ways to cause the current thread to be suspended. This one
+     * should work well in most cases. Another approach would be to use poll (NULL, 0, ) but
+     * the interval will be forced to be in ms (instead of ns or us). Note that there
+     * is a performance improvement for the lifo test when this call is made on detection
+     * of contention but it may not translate into actually MPI or application performance
+     * improvements. */
+    static struct timespec interval = {.tv_sec = 0, .tv_nsec = 100};
+    nanosleep(&interval, NULL);
+}

opal/class/opal_lifo.h

@@ -30,7 +30,6 @@
 
 #include "opal_config.h"
 #include "opal/class/opal_list.h"
-#include <time.h>
 
 #include "opal/mca/threads/mutex.h"
 #include "opal/sys/atomic.h"
@@ -92,17 +91,7 @@ opal_read_counted_pointer(volatile opal_counted_pointer_t *volatile addr,
 /**
  * @brief Helper function for lifo/fifo to sleep this thread if excessive contention is detected
  */
-static inline void _opal_lifo_release_cpu(void)
-{
-    /* NTH: there are many ways to cause the current thread to be suspended. This one
-     * should work well in most cases. Another approach would be to use poll (NULL, 0, ) but
-     * the interval will be forced to be in ms (instead of ns or us). Note that there
-     * is a performance improvement for the lifo test when this call is made on detection
-     * of contention but it may not translate into actually MPI or application performance
-     * improvements. */
-    static struct timespec interval = {.tv_sec = 0, .tv_nsec = 100};
-    nanosleep(&interval, NULL);
-}
+void opal_lifo_release_cpu(void);
 
 /* Atomic Last In First Out lists. If we are in a multi-threaded environment then the
  * atomicity is insured via the compare-and-swap operation, if not we simply do a read
@@ -225,7 +214,7 @@ static inline opal_list_item_t *opal_lifo_pop_atomic(opal_lifo_t *lifo)
         if (++attempt == 5) {
             /* deliberately suspend this thread to allow other threads to run. this should
              * only occur during periods of contention on the lifo. */
-            _opal_lifo_release_cpu();
+            opal_lifo_release_cpu();
             attempt = 0;
         }