[gcc r16-2292] libstdc++: Do not define __cpp_lib_constexpr_exceptions [PR121114]

[Tomasz Kaminski]

https://gcc.gnu.org/g:c163bbd75b600cc6d1ec752425ee895ef5b9b37d

commit r16-2292-gc163bbd75b600cc6d1ec752425ee895ef5b9b37d
Author: Tomasz Kamiński <tkaminsk@redhat.com>
Date:   Wed Jul 16 10:49:48 2025 +0200

    libstdc++: Do not define __cpp_lib_constexpr_exceptions [PR121114]
    
    Do not advertise library support for constexpr exceptions, as our
    solution to throwing by __throw_* functions from <bits/functexcept.h>,
    caues constant evaluation to fail, as these functions are not constexpr.
    
            PR libstdc++/121114
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/version.def (constexpr_exceptions): Add no_stdname
            and changed value.
            * include/bits/version.h: Regenerated.
            * testsuite/18_support/exception/version.cc: Test that macro is
            not exported.
    
    Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
    Signed-off-by: Tomasz Kaminski <tkaminsk@redhat.com>

Diff:
---
 libstdc++-v3/include/bits/version.def                  | 4 +++-
 libstdc++-v3/include/bits/version.h                    | 3 +--
 libstdc++-v3/testsuite/18_support/exception/version.cc | 7 +++----
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/libstdc++-v3/include/bits/version.def b/libstdc++-v3/include/bits/version.def
index cf0672b48224..2f70a5299275 100644
--- a/libstdc++-v3/include/bits/version.def
+++ b/libstdc++-v3/include/bits/version.def
@@ -2052,8 +2052,10 @@ ftms = {
 
 ftms = {
   name = constexpr_exceptions;
+  // TODO Remove when PR121114 is resolved
+  no_stdname = true;
   values = {
-    v = 202411;
+    v = 1; // TODO 202411;
     cxxmin = 26;
     extra_cond = "__cpp_constexpr_exceptions >= 202411L";
   };
diff --git a/libstdc++-v3/include/bits/version.h b/libstdc++-v3/include/bits/version.h
index c01ddf14dd57..8e0ae6822519 100644
--- a/libstdc++-v3/include/bits/version.h
+++ b/libstdc++-v3/include/bits/version.h
@@ -2301,9 +2301,8 @@
 
 #if !defined(__cpp_lib_constexpr_exceptions)
 # if (__cplusplus >  202302L) && (__cpp_constexpr_exceptions >= 202411L)
-#  define __glibcxx_constexpr_exceptions 202411L
+#  define __glibcxx_constexpr_exceptions 1L
 #  if defined(__glibcxx_want_all) || defined(__glibcxx_want_constexpr_exceptions)
-#   define __cpp_lib_constexpr_exceptions 202411L
 #  endif
 # endif
 #endif /* !defined(__cpp_lib_constexpr_exceptions) && defined(__glibcxx_want_constexpr_exceptions) */
diff --git a/libstdc++-v3/testsuite/18_support/exception/version.cc b/libstdc++-v3/testsuite/18_support/exception/version.cc
index 09a2d102b720..5707abd732f5 100644
--- a/libstdc++-v3/testsuite/18_support/exception/version.cc
+++ b/libstdc++-v3/testsuite/18_support/exception/version.cc
@@ -3,8 +3,7 @@
 
 #include <exception>
 
-#ifndef __cpp_lib_constexpr_exceptions
-# error "Feature test macro for constexpr_exceptions is missing in <exception>"
-#elif __cpp_lib_constexpr_exceptions < 202411L
-# error "Feature test macro for constexpr_exceptions has wrong value in <exception>"
+#ifdef __cpp_lib_constexpr_exceptions
+# error "Feature test macro for constexpr_exceptions should not be provided by <exception>"
 #endif
+