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re PR libstdc++/52699 (infinite loop generated with -O0) 

2012-04-14  Paolo Carlini  <paolo.carlini@oracle.com>

	PR libstdc++/52699
	* include/bits/random.tcc (independent_bits_engine<>::operator()())
	Avoid various overflows; use common_type on result_type and
	_RandomNumberEngine::result_type; avoid floating point computations;
	other smaller tweaks.

	* include/bits/random.tcc (uniform_int_distribution<>::operator())
	Use common_type; assume _UniformRandomNumberGenerator::result_type
	unsigned; tidy.

	* include/bits/stl_algobase.h (__lg(unsigned), __lg(unsigned long),
	__lg(unsigned long long)): Add.

From-SVN: r186456
This commit is contained in:
Paolo Carlini 2012-04-14 22:33:22 +00:00 committed by Paolo Carlini
parent 608dccd7ab
commit f84ca6e7ce
3 changed files with 73 additions and 22 deletions
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15
libstdc++-v3/ChangeLog
View File

@ -1,3 +1,18 @@
2012-04-14 Paolo Carlini <paolo.carlini@oracle.com>
PR libstdc++/52699
* include/bits/random.tcc (independent_bits_engine<>::operator()())
Avoid various overflows; use common_type on result_type and
_RandomNumberEngine::result_type; avoid floating point computations;
other smaller tweaks.
* include/bits/random.tcc (uniform_int_distribution<>::operator())
Use common_type; assume _UniformRandomNumberGenerator::result_type
unsigned; tidy.
* include/bits/stl_algobase.h (__lg(unsigned), __lg(unsigned long),
__lg(unsigned long long)): Add.
2012-04-14 Alan Modra <amodra@gmail.com>
PR libstdc++/52839

68
libstdc++-v3/include/bits/random.tcc
View File

@ -730,40 +730,65 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
independent_bits_engine<_RandomNumberEngine, __w, _UIntType>::
operator()()
{
const long double __r = static_cast<long double>(_M_b.max())
- static_cast<long double>(_M_b.min()) + 1.0L;
const result_type __m = std::log(__r) / std::log(2.0L);
result_type __n, __n0, __y0, __y1, __s0, __s1;
typedef typename _RandomNumberEngine::result_type _Eresult_type;
const _Eresult_type __r
= (_M_b.max() - _M_b.min() < std::numeric_limits<_Eresult_type>::max()
? _M_b.max() - _M_b.min() + 1 : 0);
const unsigned __edig = std::numeric_limits<_Eresult_type>::digits;
const unsigned __m = __r ? std::__lg(__r) : __edig;
typedef typename std::common_type<_Eresult_type, result_type>::type
__ctype;
const unsigned __cdig = std::numeric_limits<__ctype>::digits;
unsigned __n, __n0;
__ctype __s0, __s1, __y0, __y1;
for (size_t __i = 0; __i < 2; ++__i)
{
__n = (__w + __m - 1) / __m + __i;
__n0 = __n - __w % __n;
const result_type __w0 = __w / __n;
const result_type __w1 = __w0 + 1;
__s0 = result_type(1) << __w0;
__s1 = result_type(1) << __w1;
__y0 = __s0 * (__r / __s0);
__y1 = __s1 * (__r / __s1);
if (__r - __y0 <= __y0 / __n)
const unsigned __w0 = __w / __n; // __w0 <= __m
__s0 = 0;
__s1 = 0;
if (__w0 < __cdig)
{
__s0 = __ctype(1) << __w0;
__s1 = __s0 << 1;
}
__y0 = 0;
__y1 = 0;
if (__r)
{
__y0 = __s0 * (__r / __s0);
if (__s1)
__y1 = __s1 * (__r / __s1);
if (__r - __y0 <= __y0 / __n)
break;
}
else
break;
}
result_type __sum = 0;
for (size_t __k = 0; __k < __n0; ++__k)
{
result_type __u;
__ctype __u;
do
__u = _M_b() - _M_b.min();
while (__u >= __y0);
__sum = __s0 * __sum + __u % __s0;
while (__y0 && __u >= __y0);
__sum = __s0 * __sum + (__s0 ? __u % __s0 : __u);
}
for (size_t __k = __n0; __k < __n; ++__k)
{
result_type __u;
__ctype __u;
do
__u = _M_b() - _M_b.min();
while (__u >= __y1);
__sum = __s1 * __sum + __u % __s1;
while (__y1 && __u >= __y1);
__sum = __s1 * __sum + (__s1 ? __u % __s1 : __u);
}
return __sum;
}
@ -840,12 +865,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
operator()(_UniformRandomNumberGenerator& __urng,
const param_type& __param)
{
typedef typename std::make_unsigned<typename
_UniformRandomNumberGenerator::result_type>::type __urngtype;
typedef typename _UniformRandomNumberGenerator::result_type
_Gresult_type;
typedef typename std::make_unsigned<result_type>::type __utype;
typedef typename std::conditional<(sizeof(__urngtype)
> sizeof(__utype)),
__urngtype, __utype>::type __uctype;
typedef typename std::common_type<_Gresult_type, __utype>::type
__uctype;
const __uctype __urngmin = __urng.min();
const __uctype __urngmax = __urng.max();

12
libstdc++-v3/include/bits/stl_algobase.h
View File

@ -989,14 +989,26 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__lg(int __n)
{ return sizeof(int) * __CHAR_BIT__ - 1 - __builtin_clz(__n); }
inline unsigned
__lg(unsigned __n)
{ return sizeof(int) * __CHAR_BIT__ - 1 - __builtin_clz(__n); }
inline long
__lg(long __n)
{ return sizeof(long) * __CHAR_BIT__ - 1 - __builtin_clzl(__n); }
inline unsigned long
__lg(unsigned long __n)
{ return sizeof(long) * __CHAR_BIT__ - 1 - __builtin_clzl(__n); }
inline long long
__lg(long long __n)
{ return sizeof(long long) * __CHAR_BIT__ - 1 - __builtin_clzll(__n); }
inline unsigned long long
__lg(unsigned long long __n)
{ return sizeof(long long) * __CHAR_BIT__ - 1 - __builtin_clzll(__n); }
_GLIBCXX_END_NAMESPACE_VERSION
_GLIBCXX_BEGIN_NAMESPACE_ALGO