From 0badb9398ae81fb083e8c86fb137b31159d7bae9 Mon Sep 17 00:00:00 2001
From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Thu, 11 Jan 2024 14:31:14 -0700
Subject: [PATCH] When using C++23, use [[assume]] attribute.

---
 include/deal.II/base/config.h.in  | 21 +++++++++++++--------
 include/deal.II/base/exceptions.h |  1 +
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/include/deal.II/base/config.h.in b/include/deal.II/base/config.h.in
index c9943b3efe..5e468bc133 100644
--- a/include/deal.II/base/config.h.in
+++ b/include/deal.II/base/config.h.in
@@ -183,10 +183,13 @@
  * attribute for older standards we rely on compiler intrinsics when
  * available.
  */
-#if defined(__clang__)
-#  define DEAL_II_CXX23_ASSUME(expr) __builtin_assume(static_cast<bool>(expr))
-#elif defined(__GNUC__) && !defined(__ICC) && __GNUC__ >= 13
-#  define DEAL_II_CXX23_ASSUME(expr)                                   \
+#ifdef DEAL_II_HAVE_CXX23
+#  define define DEAL_II_ASSUME(expr) [[assume(expr)]]
+#else
+#  if defined(__clang__)
+#    define DEAL_II_CXX23_ASSUME(expr) __builtin_assume(static_cast<bool>(expr))
+#  elif defined(__GNUC__) && !defined(__ICC) && __GNUC__ >= 13
+#    define DEAL_II_CXX23_ASSUME(expr)                                   \
     do                                                                 \
       {                                                                \
         _Pragma("GCC diagnostic push")                                 \
@@ -195,17 +198,19 @@
         _Pragma("GCC diagnostic pop")                                  \
       }                                                                \
     while (false)
-#elif defined(_MSC_VER) || defined(__ICC)
-#  define DEAL_II_CXX23_ASSUME(expr) __assume(expr);
-#else
+#  elif defined(_MSC_VER) || defined(__ICC)
+#    define DEAL_II_CXX23_ASSUME(expr) __assume(expr);
+#  else
 /* no way with GCC to express this without evaluating 'expr' */
-#  define DEAL_II_CXX23_ASSUME(expr) \
+#    define DEAL_II_CXX23_ASSUME(expr) \
     do                               \
       {                              \
       }                              \
     while (false)
+#  endif
 #endif
 
+
 /**
  * Macro indicating that the current feature will be removed in a future
  * release.
diff --git a/include/deal.II/base/exceptions.h b/include/deal.II/base/exceptions.h
index 99dceb5450..4adb7483ba 100644
--- a/include/deal.II/base/exceptions.h
+++ b/include/deal.II/base/exceptions.h
@@ -1519,6 +1519,7 @@ namespace deal_II_exceptions
 } /*namespace deal_II_exceptions*/
 
 
+
 /**
  * A macro that serves as the main routine in the exception mechanism for debug
  * mode error checking. It asserts that a certain condition is fulfilled,
-- 
2.39.5