Examples of errors detected by the V567 diagnostic.

V567. Undefined behavior. The variable is modified while being used twice between sequence points.

Fennec Media

V567 Undefined behavior. The 'm_nCurrentBitIndex' variable is modified while being used twice at single sequence point. MACLib unbitarrayold.cpp 78


uint32 CUnBitArrayOld::DecodeValueRiceUnsigned(uint32 k)
{
  ...
  while (!(m_pBitArray[m_nCurrentBitIndex >> 5] &
     Powers_of_Two_Reversed[m_nCurrentBitIndex++ & 31])) {}
  ...
}

SAGA GIS

V567 Undefined behavior. The 'iFloater' variable is modified while being used twice between sequence points. shapes_lines line_simplification.cpp 248


bool CLine_Simplification::Simplify(
  CSG_Shape *pLine, int iPart, bool *Keep)
{
  ...
  Keep[iFloater--] = iAnchor == 0 && iFloater ==
    pLine->Get_Point_Count(iPart) - 1;
  ...
}

Miranda IM

V567 Undefined behavior. The 's' variable is modified while being used twice between sequence points. msn ezxml.c 371


short ezxml_internal_dtd(ezxml_root_t root, char *s,
  size_t len)
{
  ...
  while (*(n = ++s + strspn(s, EZXML_WS)) && *n != '>') {
  ...
}

It's not guaranteed that 's' will be incremented before calling the strspn function.

IPP Samples

V567 Undefined behavior. The 'pTemp' variable is modified while being used twice between sequence points. me umc_me_cost_func.h 168

V567 Undefined behavior. The 'pDst' variable is modified while being used twice between sequence points. me umc_me_cost_func.h 174


template<typename T, Ipp32s size> void HadamardFwdFast(
  ...., Ipp16s* pDst)
{
  Ipp32s *pTemp;
  ...
  for(j=0;j<4;j++) {
    a[0] = pTemp[0*4] + pTemp[1*4];
    a[1] = pTemp[0*4] - pTemp[1*4];
    a[2] = pTemp[2*4] + pTemp[3*4];
    a[3] = pTemp[2*4] - pTemp[3*4];
    pTemp = pTemp++;

    pDst[0*4] = (Ipp16s)(a[0] + a[2]);
    pDst[1*4] = (Ipp16s)(a[1] + a[3]);
    pDst[2*4] = (Ipp16s)(a[0] - a[2]);
    pDst[3*4] = (Ipp16s)(a[1] - a[3]);
    pDst = pDst++;
  }
  ...
}

Typical Undefined behavior!

Similar errors can be found in some other places:

V567 Undefined behavior. The 'pTemp' variable is modified while being used twice between sequence points. me umc_me_cost_func.h 219
V567 Undefined behavior. The 'pDst' variable is modified while being used twice between sequence points. me umc_me_cost_func.h 238

IPP Samples

V567 Undefined behavior. The 'm_curIndex' variable is modified while being used twice between sequence points. vc1_enc umc_vc1_enc_planes.h 630


bool MoveOnNextFrame()
{
  if (m_nFrames>0)
  {
    m_pFrame[m_curIndex] = 0;
    m_curIndex = (++m_curIndex)%m_maxN;
    m_nFrames--;
    return true;
  }
  return false;
}

IPP Samples

V567 Undefined behavior. The 'm_Quant.LimIQuant' variable is modified while being used twice between sequence points. vc1_enc umc_vc1_enc_brc_gop.cpp 241

V567 Undefined behavior. The 'm_Quant.IQuant' variable is modified while being used twice between sequence points. vc1_enc umc_vc1_enc_brc_gop.cpp 243


void VC1BRC_I::CompleteFrame(ePType picType)
{
  ...
  m_Quant.LimIQuant = m_Quant.LimIQuant--;
  ...
  m_Quant.IQuant = m_Quant.IQuant--;
  ...
}

Doom 3

V567 Undefined behavior. The 'dir_cache_index' variable is modified while being used twice between sequence points. TypeInfo filesystem.cpp 1877


int idFileSystemLocal::ListOSFiles(....)
{
  ...
  dir_cache_index = (++dir_cache_index) % MAX_CACHED_DIRS;
  ...
}

This is what should have been written here: dir_cache_index = (dir_cache_index + 1) % MAX_CACHED_DIRS;

ffdshow

V567 Undefined behavior. The 'm_Offset' variable is modified while being used twice between sequence points. quicksyncutils.h 257


inline bool PopFront(T& res, DWORD dwMiliSecs)
{
  ....
  m_Offset = ++m_Offset % m_Capacity;
  ....
}

Network Security Services (NSS)

V567 Undefined behavior. The 'j' variable is modified while being used twice between sequence points. pk11slot.c 1926


PK11SlotList *
PK11_GetAllTokens(....)
{
  ....
  int j = 0;
  PRInt32 waste[16];
  ....
#if defined( XP_WIN32 )
  /* This is works around some horrible cache/page thrashing
  ** problems on Win32.  Without this, this loop can take up to
  ** 6 seconds at 100% CPU on a Pentium-Pro 200.  The thing this
  ** changes is to increase the size of the stack frame and
  ** modify it. Moving the loop code itself seems to have no
  ** effect. Dunno why this combination makes a difference,
  ** but it does.
  */
  waste[j & 0xf] = j++;
#endif
  ....
}

AssaultCube Reloaded

V567 Undefined behavior. The 'fullconsole' variable is modified while being used twice between sequence points. console.h 12


template<class LINE> struct consolebuffer
{
  void toggleconsole()
  {
    extern int altconsize;
    if(!fullconsole) fullconsole = altconsize ? 1 : 2;
    else fullconsole = ++fullconsole % 3;
  }
  ....
};

Snes9x

V567 Undefined behavior. The 'outputOffset' variable is modified while being used twice between sequence points. memmap.cpp 3926


static bool8 ReadBPSPatch (Stream *r, long, int32 &rom_size)
{
  ....
  while(length--)
    patched_rom[outputOffset++] = Memory.ROM[outputOffset];
  ....
}

Source Engine SDK

V567 Undefined behavior. The 'm_nNewSequenceParity' variable is modified while being used twice between sequence points. Client (HL2) c_baseanimating.cpp 5301

V567 Undefined behavior. The 'm_nResetEventsParity' variable is modified while being used twice between sequence points. Client (HL2) c_baseanimating.cpp 5302


int m_nNewSequenceParity;
int m_nResetEventsParity;

void C_BaseAnimating::ResetSequenceInfo( void )
{
  ....
  m_nNewSequenceParity =
    ( ++m_nNewSequenceParity ) & EF_PARITY_MASK;
  m_nResetEventsParity =
    ( ++m_nResetEventsParity ) & EF_PARITY_MASK;
  ....
}

Rhino (JavaScript engine)

V567 Undefined behavior. The 'currentMap' variable is modified while being used twice between sequence points. aossessionmanager.cpp 140


u4 AOSSessionManager::threadprocSessionManager(AThread& thread)
{
  ....
  currentMap = ((++currentMap) % pThis->m_HolderSize);
  ....
}

Steamworks SDK

V567 Undefined behavior. The 'm_nCurrentLeaderboard' variable is modified while being used twice between sequence points. leaderboards.cpp 201


int m_nCurrentLeaderboard;

void CLeaderboards::OnMenuSelection(....)
{
  ....
  m_nCurrentLeaderboard = ++m_nCurrentLeaderboard % 2;
  ....
}

CryEngine 3 SDK

V567 Undefined behavior. The 'm_index' variable is modified while being used twice between sequence points. inetwork.h 2303


void AddSample( T x )
{
  m_index = ++m_index % N;
  ....
}

Scilab

V567 Undefined behavior. The 's' variable is modified while being used twice between sequence points. ezxml.c 385


short ezxml_internal_dtd(ezxml_root_t root, char *s, size_t len)
{
  ....
  while (*(n = ++s + strspn(s, EZXML_WS)) && *n != '>') {
  ....
}

Scilab

V567 Undefined behavior. The 'i' variable is modified while being used twice between sequence points. csvread.c 620


static char **replaceStrings(....)
{
  ....
  int i = 0;
  ....
  for (i = 0; i < nr; i = i++)
  ....
}

Word for Windows 1.1a

V567 Undefined behavior. The 'iBitmap' variable is modified while being used twice between sequence points. ddedit.c 107


CmdBitmap()
{
  static int  iBitmap = 0;
  ....
  iBitmap = ++iBitmap % MAXBITMAP;
}

Similar errors can be found in some other places:

V567 Undefined behavior. The 'iIcon' variable is modified while being used twice between sequence points. ddedit.c 132
V567 Undefined behavior. The 'iCursor' variable is modified while being used twice between sequence points. ddedit.c 150

Tesseract

V567 Undefined behavior. The 'num_deleted_boxes' variable is modified while being used twice between sequence points. libtesseract303 tabvector.cpp 735


void TabVector::Evaluate(....) {
  ....
  int num_deleted_boxes = 0;
  ....
  ++num_deleted_boxes = true;
  ....
}

Chromium

V567 Undefined behavior. The 'g_color_index' variable is modified while being used twice between sequence points. window_type_launcher.cc 60


int g_color_index = 0;

explicit ModalWindow(ui::ModalType modal_type) : ....
{
  ++g_color_index %= arraysize(g_colors);
  ....
}

Similar errors can be found in some other places:

V567 Undefined behavior. The 'g_color_index' variable is modified while being used twice between sequence points. window_type_launcher.cc 123

VNL

V567 Undefined behavior. The 'mz_array_position' variable is modified while being used twice between sequence points. vnl_random.cxx 174


unsigned long vnl_random::lrand32()
{
  ....
  mz_array_position = (++mz_array_position) %
                      vnl_random_array_size;
  return p2;
}

Oracle VM Virtual Box

V567 Undefined behavior. The 'curg' variable is modified while being used twice between sequence points. consoleevents.h 75


template<class C> class ConsoleEventBuffer
{
public:
  ....
  C get()
  {
    C c;
    if (full || curg != curp)
    {
      c = buf[curg];
      ++curg %= sz;             // <=
      full = false;
    }
    return c;
  }
....
};

Similar errors can be found in some other places:

V567 Undefined behavior. The 'curp' variable is modified while being used twice between sequence points. consoleevents.h 95
V567 Undefined behavior. The 'curp' variable is modified while being used twice between sequence points. consoleevents.h 122

Miranda NG

V567 Undefined behavior. The 'i' variable is modified while being used twice between sequence points. Facebook connection.cpp 191


void FacebookProto::UpdateLoop(void *)
{
  ....
  for (int i = -1; !isOffline(); i = ++i % 50)
  ....
}

Similar errors can be found in some other places:

V567 Undefined behavior. The order of argument evaluation is not defined for 'mir_snwprintf' function. The 'timeout' variable is modified while being used twice between sequence points. WhenWasIt dlg_handlers.cpp 883

Godot Engine

V567 Undefined behavior. The 'selected_track' variable is modified while being used twice between sequence points. animation_editor.cpp 1378


void AnimationKeyEditor::_track_editor_input_event(....)
{
  ....
  if (v_scroll->is_visible() && p_input.is_action("ui_page_up"))
    selected_track=selected_track--;;
  ....
}

Godot Engine

V567 Undefined behavior. The 't' variable is modified while being used twice between sequence points. tween_interpolaters.cpp 265


static real_t out(real_t t, real_t b, real_t c, real_t d)
{
  return c * ((t = t / d - 1) * t * t + 1) + b;
}

Similar errors can be found in some other places:

V567 Undefined behavior. The 't' variable is modified while being used twice between sequence points. tween_interpolaters.cpp 271
V567 Undefined behavior. The 't' variable is modified while being used twice between sequence points. tween_interpolaters.cpp 367

Unreal Engine 4

V567 Undefined behavior. The 'NextSampleIndex' variable is modified while being used twice between sequence points. performancemonitor.h 77


void Tick(double CurrentTime, float Value)
{
  ....
  NextSampleIndex = ++NextSampleIndex % SampleSize;
  ....
}

Apple II emulator

V567 Undefined behavior. The 'addr' variable is modified while being used twice between sequence points. cpu.cpp 564


void CpuSetupBenchmark ()
{
  ....
  *(mem+addr++) =
      (opcode >= BENCHOPCODES) ? 0x00 : ((addr >> 4)+1) << 4;
  ....
}

Gamer_Z eXtreme Party

V567 Undefined behavior. The 'readOffset' variable is modified while being used twice between sequence points. bitstream.h 952


template <>
  inline bool BitStream::Read(bool &var)
{
  if ( readOffset + 1 > numberOfBitsUsed )
    return false;

  if (data[ readOffset >> 3 ] & ( 0x80 >> ( readOffset++ % 8 ) ))
    var = true;
  else
    var = false;

  return true;
}

Similar errors can be found in some other places:

V567 Undefined behavior. The 'bitStream->readOffset' variable is modified while being used twice between sequence points. bitstream.cpp 194
V567 Undefined behavior. The 'bitStream->readOffset' variable is modified while being used twice between sequence points. bitstream.cpp 208

FreeSWITCH

V567 Unspecified behavior. The order of argument evaluation is not defined for 'strtol' function. Consider inspecting the 'exp' variable. switch_utils.c 3759


SWITCH_DECLARE(int) switch_number_cmp(const char *exp, int val)
{
  for (;; ++exp) {
    int a = strtol(exp, (char **)&exp, 10);
    if (*exp != '-') {
      if (a == val)
        return 1;
    } else {
      int b = strtol(++exp, (char **)&exp, 10);        // <=
      ....
    }
    if (*exp != ',')
      return 0;
  }
}

CryEngine V

V567 Undefined behavior. The 'm_current' variable is modified while being used twice between sequence points. operatorqueue.cpp 105


bool COperatorQueue::Prepare(....)
{
  ++m_current &= 1;
  m_ops[m_current].clear();
  return true;
}

Similar errors can be found in some other places:

V567 Undefined behavior. The 'itail' variable is modified while being used twice between sequence points. trimesh.cpp 3101
V567 Undefined behavior. The 'ihead' variable is modified while being used twice between sequence points. trimesh.cpp 3108
V567 Undefined behavior. The 'ivtx' variable is modified while being used twice between sequence points. boolean3d.cpp 1194
And 5 additional diagnostic messages.

CMaNGOS

V567 Undefined behavior. The 'm_uiMovePoint' variable is modified while being used twice between sequence points. boss_onyxia.cpp 405


void UpdateAI(const uint32 uiDiff) override
{
  ....
  switch (urand(0, 2))
  {
    case 0:
      ....
    case 1:
    {
        // C++ is stupid, so add -1 with +7
        m_uiMovePoint += NUM_MOVE_POINT - 1;
        m_uiMovePoint %= NUM_MOVE_POINT;
        break;
    }
    case 2:
        ++m_uiMovePoint %= NUM_MOVE_POINT; // <=
        break;
  }
  ....
}

Similar errors can be found in some other places:

V567 Undefined behavior. The 'm_uiCrystalPosition' variable is modified while being used twice between sequence points. boss_ossirian.cpp 150

Far2l

V567 Undefined behavior. The 'Item[FocusPos]->Selected' variable is modified while being used twice between sequence points. dialog.cpp 3827


int Dialog::Do_ProcessSpace()
{
  ....
  if (Item[FocusPos]->Flags&DIF_3STATE)
    (++Item[FocusPos]->Selected)%=3;         // <=
  else
    Item[FocusPos]->Selected = !Item[FocusPos]->Selected;
  ....
}

Similar errors can be found in some other places:

V567 Undefined behavior. The '::ViewerID' variable is modified while being used twice between sequence points. viewer.cpp 117

Bugs Found

int gx = gm.x.toInt();
int gy = gm.y.toInt();
int iw = gm.width.toInt();
int ih = gm.height.toInt();
if (iw <= 0 || iw <= 0)
  return 0;

UnrealEngine

C++

switch ( BlendMode )
{
case Opaque:
  BackgroundColor.A = 1.0f;
case Masked:
  BackgroundColor.A = 0.0f;
}

Xamarin

get {
  return Left == 0 &&
         Top == 0 &&
         Right == 0 &&
         Left == 0;
}

Chromium

C++

void Explode(bool is_local,
  Exploded* exploded) const
{
  ....
  ZeroMemory(
    exploded,
    sizeof(exploded));
  ....
}

Qt

C++

int gx = gm.x.toInt();
int gy = gm.y.toInt();
int iw = gm.width.toInt();
int ih = gm.height.toInt();
if (iw <= 0 || iw <= 0)
  return 0;

UnrealEngine

C++

switch ( BlendMode )
{
case Opaque:
  BackgroundColor.A = 1.0f;
case Masked:
  BackgroundColor.A = 0.0f;
}

Xamarin

get {
  return Left == 0 &&
         Top == 0 &&
         Right == 0 &&
         Left == 0;
}

Chromium

C++

void Explode(bool is_local,
  Exploded* exploded) const
{
  ....
  ZeroMemory(
    exploded,
    sizeof(exploded));
  ....
}

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