[committed] [gcc-12] libstdc++: avoid bogus -Wrestrict [PR105651]

[Jonathan Wakely via Gcc-patches]

I've pushed Jason's patch from https://gcc.gnu.org/PR105651#c17 to the
gcc-12 branch, because Jakub's fix on gcc-13 isn't possible to backport.

Tested x86_64-linux, pushed to gcc-12.

-- >8 --

        PR tree-optimization/105651

libstdc++-v3/ChangeLog:

        * include/bits/basic_string.tcc (_M_replace): Add an assert
        to avoid -Wrestrict false positive.
---
 libstdc++-v3/include/bits/basic_string.tcc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/libstdc++-v3/include/bits/basic_string.tcc 
b/libstdc++-v3/include/bits/basic_string.tcc
index 0696b96604c..48fa28e6466 100644
--- a/libstdc++-v3/include/bits/basic_string.tcc
+++ b/libstdc++-v3/include/bits/basic_string.tcc
@@ -529,6 +529,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
                    {
                      const size_type __nleft = (__p + __len1) - __s;
                      this->_S_move(__p, __s, __nleft);
+                     // Tell the middle-end that the copy can't overlap
+                     // (PR105651).
+                     if (__len2 < __nleft)
+                       __builtin_unreachable();
                      this->_S_copy(__p + __nleft, __p + __len2,
                                    __len2 - __nleft);
                    }
-- 
2.40.1