We 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.
Six Myths about Ontologies: The Basics of Formal Ontology
Static analysis of C++ source code
1. Static analysis of C++ source code KarpovAndreyNikolaevich candidate of science (PhD), CTO OOO «Program Verification Systems» (Co Ltd) E-mail: karpov@viva64.com
2. What is this report about We 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.
3. «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.
4. Priority of & and! operations ReturntoCastleWolfenstein – computer game, first person shooter, developed by id Software company. Game engine is available under GPL license. #define SVF_CASTAI 0x00000010 if ( !ent->r.svFlags& SVF_CASTAI ) if ( ! (ent->r.svFlags & SVF_CASTAI) )
5. 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);
6. Undefined behavior Miranda IM (Miranda Instant Messenger) – instant messaging software for Microsoft Windows. while (*(n = ++s + strspn(s, EZXML_WS)) && *n != '>') {
7. Usage of `delete` for an array Chromium – 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.
8. Condition is always true WinDjView 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; }
9. Code formatting differs from it’s own logic Squirrel – 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
10. Incidental local variable declaration FCE Ultra – open source Nintendo Entertainment System console emulator intiNesSaveAs(char* name) { ... fp = fopen(name,"wb"); int x = 0; if (!fp) int x = 1; ... }
11. 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.
12. Incidental use of hexadecimal values oCell._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
13. One variable is used for two loops Lugaru— 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; } ... } ... }
14. Array overrun LAME – free app for MP3 audio encoding. #define SBMAX_l22 int 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];
15. Priority of * and ++ operations eMuleis a client for ED2K file sharing network. STDMETHODIMP CCustomAutoComplete::Next(..., ULONG *pceltFetched) { ... if (pceltFetched != NULL) *pceltFetched++; ... } (*pceltFetched)++;
16. Comparison mistake WinMerge — free open source software intended for the comparison and synchronization of files and directories. BUFFERTYPE m_nBufferType[2]; ... // Handle unnamed buffers if ((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)
17. Forgotten array index void 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.
18. Identical source code branches Notepad++ - 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;
19. Calling incorrect function with similar name What 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.
20. Dangerous ?: operator NewtonGameDynamics– 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 *.
21. And so on, and so on… if (m_szPassword != NULL) { if (m_szPassword != '') { Ultimate TCP/IP library if (*m_szPassword != '') bleeding = 0; bleedx = 0,bleedy; direction = 0; Lugaru bleedx = 0; bleedy = 0;
22. And so on, and so on… if((t=(char *)realloc( next->name, strlen(name+1)))) FCE Ultra if((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);
23. Low level memory management operations I want to discuss separately the heritage of programs whish were using the following functions: ZeroMemory; memset; memcpy; memcmp; …
26. Low level memory management operations A 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.
28. Low level memory management operations OGRE — 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!
30. 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 algorithms interface
31. 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 (*.*)*.*"); lofn.lpstrFilter = uni("All Files (*.*)*.*");
32. 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); ... }
