[Bug libstdc++/60441] Incorrect textual representation for std::mersenne_twister_engine

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60441

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2018-08-07 00:00:00         |2023-5-23

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The fix is quite simple, but it breaks compatibility between releases:

diff --git a/libstdc++-v3/include/bits/random.tcc
b/libstdc++-v3/include/bits/random.tcc
index 24a5987db0d..8f53d5c5f53 100644
--- a/libstdc++-v3/include/bits/random.tcc
+++ b/libstdc++-v3/include/bits/random.tcc
@@ -486,9 +486,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       __os.flags(__ios_base::dec | __ios_base::fixed | __ios_base::left);
       __os.fill(__space);

-      for (size_t __i = 0; __i < __n; ++__i)
+      for (size_t __i = __x._M_p; __i < __n; ++__i)
+       __os << __x._M_x[__i] << __space;
+      for (size_t __i = 0; __i < __x._M_p; ++__i)
        __os << __x._M_x[__i] << __space;
-      __os << __x._M_p;

       __os.flags(__flags);
       __os.fill(__fill);
@@ -512,7 +513,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION

       for (size_t __i = 0; __i < __n; ++__i)
        __is >> __x._M_x[__i];
-      __is >> __x._M_p;
+      __x._M_p = 0;

       __is.flags(__flags);
       return __is;