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Things to Remember When Developing 64-bit Software

Things to Remember When Developing 64-bit Software. OOO " Program Verification Systems " www.viva64.com. Advantages of 64-bit Software. You can store all the data right in memory Performance boost ( when the data format is chosen correctly )

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Things to Remember When Developing 64-bit Software

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  1. Things to Remember When Developing 64-bit Software OOO"Program Verification Systems" www.viva64.com

  2. Advantages of 64-bit Software • You can store all the data right in memory • Performance boost (when the data format is chosen correctly) • Additional performance boost due to architectural solutions • No resources wasted to pass through theWoW64 layer

  3. Differences in Programming • No differences. C/C++ is a language designed to develop crossplatform applications • Only the data model is different • But in practice, programs are not completely crossplatform • A compiled 64-bit program != a correct 64-bit program Who can write ideal, spherical code?

  4. What Has Changed? • Pointer size: 4 bytes -> 8 bytes. • Sizes of types size_t, ptrdiff_t, intptr_t, uintptr_t, INT_PTR, UINTPTR_T: 4 bytes-> 8 bytes. • Data alignment. Mind it when serializing structures. • Array index size. • So few? More than enough for troubles!

  5. From Simple to Complex.Magic Numbers hFileMapping =CreateFileMapping( (HANDLE) 0xFFFFFFFF,NULL,PAGE_READWRITE, (DWORD) 0, (DWORD) (szBufIm), (LPCTSTR) &FileShareNameMap[0]); //Number 0xFFFFFFFF is “usignedint”. The fixed code: #define INVALID_HANDLE_VALUE ((HANDLE)(LONG_PTR)-1)

  6. Storing Pointers in a 32-bit Variable char *ptr = ...; int n = (int) ptr; ... ptr = (char *) n; A very annoying bug. It only occurs when the program is running for a long time.

  7. The Most Important Thing to Remember with 64-bit Development • The pointer is not the same thing as intor long. By the way, the long type is different in the data models LP64 andLLP64. It also adds some more confusion. • Don’t use 32-bit types and address arithmetic together.Use these types: • size_t • ptrdiff_t • intptr_t • uintptr_t • INT_PTR, ….

  8. A More Creative Solution for Pointer Storage int*p1, *p2; .... char str[128]; sprintf(str, "%X %X", p1, p2); int*p1, *p2; sscanf(str, "%X %X", &p1, &p2); Use “%p” to print pointer values.Also, programmers often incorrectly print size_t variables.“%Iu” should be used for this purpose. const char *invalidFormat = "%u"; size_t value = SIZE_MAX; printf(invalidFormat, value);

  9. A few more words about functions with variable number of arguments

  10. Implicit Type Conversion unsigned n = it->find("ABC"); if (n != string::npos) return true;

  11. Address Arithmetic. Signed and Unsigned Types float p1[100]; unsigned x = 5; int y = -1; float *p2 = p1 + 50; p2 = p2 + x * y; // Access violation *p2 = 1.0f; Correct code!!!!!!!!!!!!!!!!!!!!!!!!!!

  12. Address Arithmetic. Overflows. extern int Width, Height, Depth; size_tGetIndex(int x, int y, int z) { return z * Width * Height + y * Width + x; } ... MyArray[GetIndex(x, y, z)] = 0.0f; These errors reveal themselves only at LARGE data amounts. Unit tests won’t help you here, neither will dynamic analyzers such as Bounds Checker (it is too slow). return size_t(z) * Width * Height + size_t(y) * Width + x;

  13. Incorrect Solutions return size_t(z * Width * Height + y * Width + x); return size_t(z) * Width * Height + y * Width + x;

  14. Infinite Loops P.S. The funny thing is that infinite loops sometimes fail to occur – thanks to compiler-performed optimization.

  15. Obsolete typedefand#ifdef //A do-it-yourselfthing in one file typedefunsigned UINT_PTR; #ifdef _MY_BUILD_32 // Win32 const unsigned BufferSize = 1024*1024; #else // Win16 constunsigned BufferSize = 16*1024; #endif

  16. Exotic Issues:Buffer Overflow

  17. Structure Size Growth structMyStruct { boolm_bool; char *m_pointer; intm_int; }; structMyStructOpt { char *m_pointer; intm_int; boolm_bool; };

  18. Other Issues • Use of deprecated functions (SetClassLong, GetClassLong, GetFileSize, EnumProcessModules, GlobalMemoryStatus) • Undeclared functions in C • Different parameters of virtual functions • Array type change • Pointers in unions • Exceptions • And so on…

  19. How to Prepare a Reliable 64-bit Version of a Product? • Unit-tests (but don’t rely solely on them) • Regression tests • Compiler warning elimination • Using specialized tools, for example the Viva64 rule set included into the PVS-Studio static analyzer.

  20. PVS-Studio • Rule sets: • The most powerful analysis for 64-bit errors among other similar tools • General diagnostics • Micro optimizations • OpenMP • About the tool:http://www.viva64.com/en/pvs-studio/ • Download:http://www.viva64.com/en/pvs-studio-download/

  21. Visual Studio Integration

  22. C++Builder Integration

  23. References • Lessons on development of 64-bit C/C++ applications. http://www.viva64.com/en/l/ • An article. A Collection of Examples of 64-bit Errors in Real Programs. http://www.viva64.com/en/a/0065 • Article reviews http://www.viva64.com/en/r/tag/x64/ • Knowledge base http://www.viva64.com/en/k/

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