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| author | Jonathan Wakely <jwakely@redhat.com> | 2016-11-15 20:17:39 +0000 |
|---|---|---|
| committer | Jonathan Wakely <redi@gcc.gnu.org> | 2016-11-15 20:17:39 +0000 |
| commit | 27b3b3f4e68e584c6caa83088d87caa121d83796 (patch) | |
| tree | f93eb9a075bea8a122905302101393b6f73732b3 | |
| parent | 3663671a13e12efe283d1b04df5416cedb796e86 (diff) | |
| download | gcc-27b3b3f4e68e584c6caa83088d87caa121d83796.zip gcc-27b3b3f4e68e584c6caa83088d87caa121d83796.tar.gz gcc-27b3b3f4e68e584c6caa83088d87caa121d83796.tar.bz2 | |
PR 59406 note that FNV hash functions are incorrect
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
| -rw-r--r-- | libstdc++-v3/ChangeLog | 6 | ||||
| -rw-r--r-- | libstdc++-v3/include/bits/functional_hash.h | 1 | ||||
| -rw-r--r-- | libstdc++-v3/include/tr1/functional_hash.h | 4 | ||||
| -rw-r--r-- | libstdc++-v3/libsupc++/hash_bytes.cc | 6 |
4 files changed, 17 insertions, 0 deletions
diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog index 4bba6a4..d82aaa4 100644 --- a/libstdc++-v3/ChangeLog +++ b/libstdc++-v3/ChangeLog @@ -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. diff --git a/libstdc++-v3/include/bits/functional_hash.h b/libstdc++-v3/include/bits/functional_hash.h index dc09683..cee1ea8 100644 --- a/libstdc++-v3/include/bits/functional_hash.h +++ b/libstdc++-v3/include/bits/functional_hash.h @@ -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 diff --git a/libstdc++-v3/include/tr1/functional_hash.h b/libstdc++-v3/include/tr1/functional_hash.h index 4edc49a..8148e4d 100644 --- a/libstdc++-v3/include/tr1/functional_hash.h +++ b/libstdc++-v3/include/tr1/functional_hash.h @@ -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 diff --git a/libstdc++-v3/libsupc++/hash_bytes.cc b/libstdc++-v3/libsupc++/hash_bytes.cc index 1042de6..7d76c34 100644 --- a/libstdc++-v3/libsupc++/hash_bytes.cc +++ b/libstdc++-v3/libsupc++/hash_bytes.cc @@ -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) { |