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Cleaned up code to tame the optimizer in smart_ptr and member_ptr. It should work on all platforms

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This commit is contained in:
Jeffrey Walton 2015-08-02 02:11:46 -04:00
parent b44546be11
commit 24047196b1
1 changed files with 10 additions and 25 deletions
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35
smartptr.h
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@ -7,24 +7,8 @@
NAMESPACE_BEGIN(CryptoPP)
// Hack ahead. Apple's standard library does not have C++'s unique_ptr in C++11. We can't
// test for unique_ptr directly because some of the non-Apple Clangs on OS X fail the same
// way. However, modern standard libraries have <forward_list>, so we test for it instead.
// Thanks to Jonathan Wakely for devising the clever test for modern/ancient versions.
// Visual Studio did not add template aliases until VS 2015 (v19.00). Compile failed under
// Visual Studio 2010 (v16.00) and Visual Studio 2012 (v17.00).
#if (__cplusplus >= 201103L) || (_MSC_VER >= 1900)
# if defined(__clang__)
# if (__has_include(<forward_list>))
# define CRYPTOPP_HAVE_UNIQUE_PTR 1
# endif
# else
# define CRYPTOPP_HAVE_UNIQUE_PTR 1
# endif
#endif
// The result of below is a CryptoPP::auto_ptr in both cases
#ifdef CRYPTOPP_HAVE_UNIQUE_PTR
// CryptoPP::auto_ptr in created in both cases
#if defined(CRYPTOPP_CXX11_UNIQUE_PTR) && defined(CRYPTOPP_CXX11_TEMPLATE_ALIAS)
template<typename T>
using auto_ptr = std::unique_ptr<T>;
#else
@ -49,11 +33,14 @@ private:
template <class T> simple_ptr<T>::~simple_ptr()
{
delete m_p;
m_p = NULL;
*((volatile T**)(&m_p)) = 0;
// Ensure the assignment is always performed. MSVC and Clang provide expected
// operational behavior for volatile. GCC has a more strict interpretation of
// the keyword (see http://www.airs.com/blog/archives/154), and volatile
// should not be used to tame the optimizer. However, inline assembly
// will tame it (see https://gcc.gnu.org/ml/gcc-help/2015-07/msg00053.html).
#ifdef __GNUC__
// From Andrew Haley (GCC Dev), to tame the optimizer so the assignment is always performed.
// See "Disable optimizations in one function" on the GCC mailing list.
asm volatile ("" : : : "memory");
#endif
}
@ -77,12 +64,10 @@ public:
T* release()
{
T *old_p = m_p;
m_p = 0;
*((volatile T**)(&m_p)) = 0;
return old_p;
#ifdef __GNUC__
// From Andrew Haley (GCC Dev), to tame the optimizer so the assignment is always performed.
// See "Disable optimizations in one function" on the GCC mailing list.
asm volatile ("" : : : "memory");
#endif
}