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Secure __next_prime from overflowing 

llvm-svn: 117650
This commit is contained in:
Howard Hinnant 2010-10-29 14:10:30 +00:00
parent 08b8c534f7
commit 5ec1826429
1 changed files with 24 additions and 0 deletions
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24
libcxx/src/hash.cpp
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@ -9,6 +9,7 @@
#include "__hash_table"
#include "algorithm"
#include "stdexcept"
_LIBCPP_BEGIN_NAMESPACE_STD
@ -143,6 +144,26 @@ const unsigned indices[] =
// are fewer potential primes to search, and fewer potential primes to divide
// against.
inline _LIBCPP_INLINE_VISIBILITY
void
__check_for_overflow(size_t N, integral_constant<size_t, 32>)
{
#ifndef _LIBCPP_NO_EXCEPTIONS
if (N > 0xFFFFFFFB)
throw overflow_error("__next_prime overflow");
#endif
}
inline _LIBCPP_INLINE_VISIBILITY
void
__check_for_overflow(size_t N, integral_constant<size_t, 64>)
{
#ifndef _LIBCPP_NO_EXCEPTIONS
if (N > 0xFFFFFFFFFFFFFFC5ull)
throw overflow_error("__next_prime overflow");
#endif
}
size_t
__next_prime(size_t n)
{
@ -152,6 +173,9 @@ __next_prime(size_t n)
if (n <= small_primes[N-1])
return *std::lower_bound(small_primes, small_primes + N, n);
// Else n > largest small_primes
// Check for overflow
__check_for_overflow(n, integral_constant<size_t,
sizeof(n) * __CHAR_BIT__>());
// Start searching list of potential primes: L * k0 + indices[in]
const size_t M = sizeof(indices) / sizeof(indices[0]);
// Select first potential prime >= n