[PATCH] libstdc++: Do not define __cpp_lib_constexpr_exceptions [PR121114]

[Tomasz Kamiński]

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.
---
Tested on x86_64-linux locally. OK for trunk?

 libstdc++-v3/include/bits/version.def                  | 6 ++++--
 libstdc++-v3/include/bits/version.h                    | 3 +--
 libstdc++-v3/testsuite/18_support/exception/version.cc | 7 +++----
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/libstdc++-v3/include/bits/version.def 
b/libstdc++-v3/include/bits/version.def
index cf0672b4822..addc60f27f3 100644
--- a/libstdc++-v3/include/bits/version.def
+++ b/libstdc++-v3/include/bits/version.def
@@ -2051,9 +2051,11 @@ ftms = {
 };
 
 ftms = {
-  name = constexpr_exceptions;
+  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 c01ddf14dd5..8e0ae682251 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 09a2d102b72..5707abd732f 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
+
-- 
2.49.0