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[committed] libstdc++: Do not use memset in _Hashtable::clear()

Message ID 20240612150341.808599-1-jwakely@redhat.com
State New
Headers show
Series [committed] libstdc++: Do not use memset in _Hashtable::clear() | expand

Commit Message

Jonathan Wakely June 12, 2024, 2:07 p.m. UTC 
Tested x86_64-linux. Pushed to trunk.

-- >8 --

Using memset is incorrect if the __bucket_ptr type is non-trivial, or
does not use an all-zero bit pattern for its null value.

Replace the three uses of memset with std::fill_n to set the pointers to
nullptr.

libstdc++-v3/ChangeLog:

	* include/bits/hashtable.h (_Hashtable::clear): Do not use
	memset to zero out bucket pointers.
	(_Hashtable::_M_assign_elements): Likewise.
---
 libstdc++-v3/include/bits/hashtable.h | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)
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Patch

diff --git a/libstdc++-v3/include/bits/hashtable.h b/libstdc++-v3/include/bits/hashtable.h
index 6e78cb7d9c0..983aa909d6c 100644
--- a/libstdc++-v3/include/bits/hashtable.h
+++ b/libstdc++-v3/include/bits/hashtable.h
@@ -34,6 +34,7 @@ 
 
 #include <bits/hashtable_policy.h>
 #include <bits/enable_special_members.h>
+#include <bits/stl_algobase.h> // fill_n
 #include <bits/stl_function.h> // __has_is_transparent_t
 #if __cplusplus > 201402L
 # include <bits/node_handle.h>
@@ -1376,8 +1377,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	    _M_bucket_count = __ht._M_bucket_count;
 	  }
 	else
-	  __builtin_memset(_M_buckets, 0,
-			   _M_bucket_count * sizeof(__node_base_ptr));
+	  std::fill_n(_M_buckets, _M_bucket_count, nullptr);
 
 	__try
 	  {
@@ -1400,8 +1400,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
 		_M_buckets = __former_buckets;
 		_M_bucket_count = __former_bucket_count;
 	      }
-	    __builtin_memset(_M_buckets, 0,
-			     _M_bucket_count * sizeof(__node_base_ptr));
+	    std::fill_n(_M_buckets, _M_bucket_count, nullptr);
 	    __throw_exception_again;
 	  }
       }
@@ -2582,8 +2581,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
     clear() noexcept
     {
       this->_M_deallocate_nodes(_M_begin());
-      __builtin_memset(_M_buckets, 0,
-		       _M_bucket_count * sizeof(__node_base_ptr));
+      std::fill_n(_M_buckets, _M_bucket_count, nullptr);
       _M_element_count = 0;
       _M_before_begin._M_nxt = nullptr;
     }