Static analysis of C++ source code

Static analysis of C++ source codeKarpovAndreyNikolaevichcandidate of science (PhD), CTOOOO «Program Verification Systems» (Co Ltd)E-mail: karpov@viva64.com

What is this report aboutWe all make mistakes while programming and spend a lot of time fixing them.One of the methods which allows for quick detection of defects is source code static analysis.

«One should write a quality code from the beginning» - it is not working in practice!even the best developers make mistakes and typing errors;following are the examples of mistakes detected by static code analyzer in a well known projects;PVS-Studio tool was used to perform the analysis.

Priority of & and! operationsReturntoCastleWolfenstein – computer game, first person shooter, developed by id Software company. Game engine is available under GPL license.#define SVF_CASTAI 0x00000010if ( !ent->r.svFlags& SVF_CASTAI )if ( ! (ent->r.svFlags & SVF_CASTAI) )

Usage of && instead of &Stickies– yellow sticky notes, just only on your monitor.#define REO_INPLACEACTIVE (0x02000000L)#define REO_OPEN (0x04000000L)if (reObj.dwFlags&& REO_INPLACEACTIVE)m_pRichEditOle->InPlaceDeactivate();if(reObj.dwFlags&& REO_OPEN) hr = reObj.poleobj->Close(OLECLOSE_NOSAVE);

Undefined behaviorMiranda IM (Miranda Instant Messenger) – instant messaging software for Microsoft Windows.while (*(n = ++s + strspn(s, EZXML_WS)) && *n != '>') {

Usage of `delete` for an arrayChromium – open source web browser developed by Google. The development of GoogleChrome browser is based upon Chromium.auto_ptr<VARIANT> child_array(new VARIANT[child_count]);You should not useauto_ptr with arrays. Only one element is destroyed inside auto_ptr destructor:~auto_ptr() { delete _Myptr;}For example you can use boost::scoped_array as an alternative.

Condition is always trueWinDjView is fast and small app for viewing files of DjVu format.inline boolIsValidChar(int c){ return c == 0x9 || 0xA || c == 0xD || c >= 0x20 && c <= 0xD7FF || c >= 0xE000 && c <= 0xFFFD || c >= 0x10000 && c <= 0x10FFFF;}

Code formatting differs from it’s own logicSquirrel – interpreted programming language, which is developed to be used as a scripting language in real time applications such as computer games. if(pushval != 0) if(pushval) v->GetUp(-1) = t; else v->Pop(1);v->Pop(1); - will never be reached

Incidental local variable declarationFCE Ultra – open source Nintendo Entertainment System console emulatorintiNesSaveAs(char* name){ ...fp = fopen(name,"wb");int x = 0; if (!fp)int x = 1; ...}

Using char asunsigned char// check each line for illegal utf8 sequences.// If one is found, we treatthe file as ASCII,// otherwise we assumean UTF8 file.char * utf8CheckBuf = lineptr;while ((bUTF8)&&(*utf8CheckBuf)){ if ((*utf8CheckBuf == 0xC0)|| (*utf8CheckBuf == 0xC1)|| (*utf8CheckBuf >= 0xF5)) { bUTF8 = false; break; }TortoiseSVN — client of Subversion revision control system, implemented as Windows shell extension.

Incidental use of hexadecimal valuesoCell._luminance = uint16(0.2220f*iPixel._red +0.7067f*iPixel._blue +0.0713f*iPixel._green);....oCell._luminance = 2220*iPixel._red +7067*iPixel._blue +0713*iPixel._green;eLynx Image Processing SDK and Lab

One variable is used for two loopsLugaru— first commercial game developed by WolfireGamesindependent team.static inti,j,k,l,m;...for(j=0; j<numrepeats; j++){ ... for(i=0; i<num_joints; i++){ ... for(j=0;j<num_joints;j++){ if(joints[j].locked)freely=0; } ... } ...}

Array overrunLAME – free app for MP3 audio encoding. #define SBMAX_l22int l[1+SBMAX_l]; for (r0 = 0; r0 < 16; r0++) { ... for (r1 = 0; r1 < 8; r1++) { int a2 = gfc->scalefac_band.l[r0 + r1 + 2];

Priority of * and ++ operationseMuleis a client for ED2K file sharing network. STDMETHODIMP CCustomAutoComplete::Next(...,ULONG *pceltFetched){ ... if (pceltFetched != NULL) *pceltFetched++; ...}(*pceltFetched)++;

Comparison mistakeWinMerge — free open source software intended for the comparison and synchronization of files and directories.BUFFERTYPE m_nBufferType[2];...// Handle unnamed buffersif ((m_nBufferType[nBuffer] == BUFFER_UNNAMED) || (m_nBufferType[nBuffer] == BUFFER_UNNAMED))nSaveErrorCode = SAVE_NO_FILENAME;By reviewing the code close by, this should contain:(m_nBufferType[0] == BUFFER_UNNAMED) ||(m_nBufferType[1] == BUFFER_UNNAMED)

Forgotten array indexvoid lNormalizeVector_32f_P3IM(..., Ipp32s* mask, ...) { Ipp32s i; Ipp32f norm; for(i=0; i<len; i++) { if(mask<0) continue; ...}}if(mask[i]<0) continue;IPP Samplesaresamples demonstrating how to work with Intel Performance Primitives Library 7.0.

Identical source code branchesNotepad++ - free text editor for Windows supporting syntax highlight for a variety of programming languages. if (!_isVertical) Flags |=DT_VCENTER; else Flags |= DT_BOTTOM;if (!_isVertical) Flags |= DT_BOTTOM;else Flags |= DT_BOTTOM;

Calling incorrect function with similar nameWhat a beautiful comment. But it is sad that here we’re doing not what was intended./** Deletes all previous field specifiers. * This should be used when dealing * with clients that send multiple NEP_PACKET_SPEC * messages, so only the lastPacketSpec is taken * into account. */intNEPContext::resetClientFieldSpecs(){ this->fspecs.empty(); return OP_SUCCESS;} /* End of resetClientFieldSpecs() */Nmap Security Scanner – free utility intended for diverse customizable scanning of IP-networks with any number of objects and for identification of the statuses of the objects belonging to the network which is being scanned.

Dangerous ?: operatorNewtonGameDynamics– a well known physics engine which allows for reliable and fast simulation of environmental object’s physical behavior.den = dgFloat32 (1.0e-24f) * (den > dgFloat32(0.0f)) ? dgFloat32(1.0f) : dgFloat32(-1.0f);The priority of ?: is lower than that of multiplication operator *.

And so on, and so on…if (m_szPassword != NULL){if (m_szPassword != '\0') {Ultimate TCP/IP libraryif (*m_szPassword != '\0')bleeding = 0;bleedx = 0,bleedy;direction = 0;Lugarubleedx = 0;bleedy = 0;

And so on, and so on…if((t=(char *)realloc( next->name, strlen(name+1))))FCE Ultraif((t=(char *)realloc( next->name, strlen(name)+1)))minX=max(0,minX+mcLeftStart-2);minY=max(0,minY+mcTopStart-2);maxX=min((int)width,maxX+mcRightEnd-1);maxY=min((int)height,maxX+mcBottomEnd-1);minX=max(0,minX+mcLeftStart-2);minY=max(0,minY+mcTopStart-2);maxX=min((int)width,maxX+mcRightEnd-1);maxY=min((int)height,maxY+mcBottomEnd-1);

Low level memory management operationsI want to discuss separately the heritage of programs whish were using the following functions:ZeroMemory;memset;memcpy;memcmp;…

Low level memory management operationsID_INLINE mat3_t::mat3_t( float src[3][3] ){memcpy( mat, src, sizeof( src ) );}Return to Castle WolfensteinID_INLINE mat3_t::mat3_t( float (&src)[3][3] ){memcpy( mat, src, sizeof( src ) );}itemInfo_t *itemInfo;memset( itemInfo, 0, sizeof( &itemInfo ) );memset( itemInfo, 0, sizeof( *itemInfo ) );

Low level memory management operationsCxImage – open image processing library.memset(tcmpt->stepsizes, 0,sizeof(tcmpt->numstepsizes * sizeof(uint_fast16_t)));memset(tcmpt->stepsizes, 0,tcmpt->numstepsizes * sizeof(uint_fast16_t));

Low level memory management operationsA beautiful example of 64-bit error:dgInt32 faceOffsetHitogram[256];dgSubMesh* mainSegmenst[256];memset (faceOffsetHitogram, 0, sizeof (faceOffsetHitogram));memset (mainSegmenst, 0, sizeof (faceOffsetHitogram));This code was duplicated but was not entirely corrected. As a result the size of pointer will not be equal to the size of dgInt32 type on Win64 and we will flush only a fraction of mainSegmenst array.

Low level memory management operations#define CONT_MAP_MAX 50int _iContMap[CONT_MAP_MAX];...memset(_iContMap, -1, CONT_MAP_MAX);memset(_iContMap, -1, CONT_MAP_MAX * sizeof(int));

Low level memory management operationsOGRE — open source Object-OrientedGraphicsRenderingEngine written in C++.Real w, x, y, z;...inline Quaternion(Real* valptr){memcpy(&w, valptr, sizeof(Real)*4);}Yes, at present this is not a mistake.But it is a landmine!

But why not the unit-tests only?The verification of such code parts which rarely gain control;Detection of floating bugs (undefined behavior, heisenbugs);Not all variations of source code can be covered by unit tests:Complicated calculation algorithmsinterface

Unit test will not be able to help you here, but static analysis will.FennecMediaProject– universal media-player intended for high definition audio and video playback.OPENFILENAME lofn;...lofn.lpstrFilter = uni("All Files (*.*)\0*.*");lofn.lpstrFilter = uni("All Files (*.*)\0*.*\0");

Unit test will not be able to help you here, but static analysis will.static INT_PTR CALLBACK DlgProcTrayOpts(...){ ...EnableWindow(GetDlgItem(hwndDlg,IDC_PRIMARYSTATUS),TRUE);EnableWindow(GetDlgItem(hwndDlg,IDC_CYCLETIMESPIN),FALSE);EnableWindow(GetDlgItem(hwndDlg,IDC_CYCLETIME),FALSE); EnableWindow(GetDlgItem(hwndDlg,IDC_ALWAYSPRIMARY),FALSE);EnableWindow(GetDlgItem(hwndDlg,IDC_ALWAYSPRIMARY),FALSE);EnableWindow(GetDlgItem(hwndDlg,IDC_CYCLE),FALSE);EnableWindow(GetDlgItem(hwndDlg,IDC_MULTITRAY),FALSE); ...}

Where can I more details about PVS-Studio?PVS-Studio – static code analyzer intended for the detection of errors in the source code of applications developed with C/C++/C++0x. Language.Product page: http://www.viva64.com/en/pvs-studio/

Trial version: http://www.viva64.com/en/pvs-studio-download/

Static analysis of C++ source code

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