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PR 59406 note that FNV hash functions are incorrect

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PR libstdc++/59406
	* include/bits/functional_hash.h: Add comment noting difference from
	FNV-1a.
	* include/tr1/functional_hash.h: Likewise.
	* libsupc++/hash_bytes.cc: Likewise.

From-SVN: r242454
This commit is contained in:
Jonathan Wakely 2016-11-15 20:17:39 +00:00 committed by Jonathan Wakely
parent 3663671a13
commit 27b3b3f4e6
4 changed files with 17 additions and 0 deletions
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6
libstdc++-v3/ChangeLog
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@ -1,5 +1,11 @@
2016-11-15 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/59406
* include/bits/functional_hash.h: Add comment noting difference from
FNV-1a.
* include/tr1/functional_hash.h: Likewise.
* libsupc++/hash_bytes.cc: Likewise.
* include/bits/basic_string.h: Reuse _If_sv alias template for new
constructor.

1
libstdc++-v3/include/bits/functional_hash.h
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@ -200,6 +200,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ return hash(&__val, sizeof(__val), __hash); }
};
// A hash function similar to FNV-1a (see PR59406 for how it differs).
struct _Fnv_hash_impl
{
static size_t

4
libstdc++-v3/include/tr1/functional_hash.h
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@ -83,6 +83,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// Fowler / Noll / Vo (FNV) Hash (type FNV-1a)
// (Used by the next specializations of std::tr1::hash.)
// N.B. These functions should work on unsigned char, otherwise they do not
// correctly implement the FNV-1a algorithm (see PR59406).
// The existing behaviour is retained for backwards compatibility.
/// Dummy generic implementation (for sizeof(size_t) != 4, 8).
template<size_t>
struct _Fnv_hash_base

6
libstdc++-v3/libsupc++/hash_bytes.cc
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@ -112,6 +112,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
// Implementation of FNV hash for 32-bit size_t.
// N.B. This function should work on unsigned char, otherwise it does not
// correctly implement the FNV-1a algorithm (see PR59406).
// The existing behaviour is retained for backwards compatibility.
size_t
_Fnv_hash_bytes(const void* ptr, size_t len, size_t hash)
{
@ -157,6 +160,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
// Implementation of FNV hash for 64-bit size_t.
// N.B. This function should work on unsigned char, otherwise it does not
// correctly implement the FNV-1a algorithm (see PR59406).
// The existing behaviour is retained for backwards compatibility.
size_t
_Fnv_hash_bytes(const void* ptr, size_t len, size_t hash)
{