Purpose, abilities and system requirements of PVS-Studio
Installation of PVS-Studio
Getting acquainted with PVS-Studio
Correction of errors
Working with the list of diagnostic warnings
Should all the potential errors detected by the analyzer be corrected?
The article is a tutorial on operating PVS-Studio code analyzer. You will learn about the basic abilities of PVS-Studio, the principles of working with the tool and also about the peculiarities of analyzing the code of applications of some types.
PVS-Studio is a static code analyzer intended for developers of modern resource-intensive C and C++ applications. By modern applications we understand 64-bit and/or parallel applications. Development of such programs involves some difficulties different from the problems you face when developing conventional programs. For besides usual errors known to everybody like uninitialized pointers, access out of an array's limits and other code defects, which are detected by any compiler, there are new types of problems.
Figure 1 - PVS-Studio code analyzer's logo
We speak about the errors in programs which occur when porting 32-bit applications on 64-bit platforms or paralleling the code to provide support of multi-processor or multi-core mode. It is rather difficult to develop such applications because of lack of tools which could simplify creation of 64-bit and parallel programs. PVS-Studio analyzer is quite a tool for this purpose!
Although PVS-Studio code analyzer is in itself rather simple, still you should understand the principles and technology of static code analysis to use it more efficiently. After reading this article and examining the examples described in it, you will be able to use PVS-Studio in your everyday work.
The static code analyzer PVS-Studio is intended for developers of modern resource-intensive C and C++ applications. At present, PVS-Studio includes two units:
With the help of these two units PVS-Studio allows you to detect in the source code of C and C++ programs the following types of defects:
PVS-Studio analyzer is intended for working on Windows-platform. It integrates into Microsoft Visual Studio 2005/2008 development environment. The system requirements to the analyzer coincide with the requirements to Microsoft Visual Studio:
After getting PVS-Studio installation package you can begin installing the program. Fortunately, this is quite a simple procedure and the installer asks no tricky questions.
Figure 2 - Installation of PVS-Studio
During installation, the code analyzer will integrate into Microsoft Visual Studio. In case you have only one version of Microsoft Visual Studio (for example, only 2005 or 2008) installed on your computer the analyzer will integrate only into it. If you have several versions, it will integrate into all of them. It is detected automatically.
Besides, PVS-Studio Help system will integrate into MSDN. PVS-Studio has a very good Help system which contains descriptions of all the diagnostic warnings of the analyzer with examples of code defects and ways to correct them. Besides, it also describes all the settings with the help of which you can achieve better diagnosis in PVS-Studio.
When installation of PVS-Studio is complete you can make sure that it has been installed correctly. For this launch Microsoft Visual Studio and in the start window you will see the logo of PVS-Studio (Figure 3).
Figure 3 - Microsoft Visual Studio start window with PVS-Studio logo
Although you can begin working at once, we recommend that you install two additional examples of source codes PortSample and ParallelSample (Figure 4) from PVS-Studio\Issues Examples menu.
Figure 4 - Installation of additional examples of errors PortSample and ParallelSample
With the help of these examples you can get acquainted in practice with the defects which are characteristic of modern software. PortSample contains examples of problems occurring when porting software from 32-bit systems on 64-bit ones. ParallelSample allows you to see in practice what you can expect from parallel programs containing "parallel" errors.
These examples (PortSample and ParallelSample) should be installed because the further description in this article will be based on them.
After installing the examples PortSample and ParallelSample you can start examining PVS-Studio. Open PortSample (vs2008) project in Microsoft Visual Studio 2008 although you can do the same in Microsoft Visual Studio 2005 (Figure 5).
Figure 5 - Selection of PortSample demo-project
You should begin working with PVS-Studio with one of our demo-projects due to some reasons:
So, open PortSample project, select 64-bit configuration x64 to check presence of defects in 64-bit code, with the help of PVS-Studio command bar select analysis of 64-bit problems - Viva64 unit "64-bit issues (Viva64)" and launch analysis of the whole solution by the command "Check Solution". All this is shown on Figure 6.
Figure 6 - Check of PortSample solution on presence of 64-bit problems
x64 configuration is chosen deliberately. You can check only the 64-bit configuration on 64-bit code problems. The point is that the project's settings in the 64-bit configuration are different from those of the 32-bit one. So you cannot perform check of 64-bit code in the 32-bit configuration.
After launching analysis, you will see a progress indicator with Pause (pause analysis) and Stop (stop analysis) buttons on the screen. Potentially unsafe constructions detected during analysis will be printed in the window of detected defects (Figure 7).
Figure 7 - Analysis of the project - problems detected in the code are printed in the window at once
The term "potentially unsafe construction" means that the analyzer considered some particular code line a defect. But only the programmer who knows the application can determine if this line is really a defect of the application or not. This principle of working with code analyzers must be understood correctly. Generally, no tool can replace a programmer completely when solving the task of correcting errors in programs. Only a programmer can do it relying on his knowledge. But a tool can and must help the programmer in this task. That's why a code analyzer's task is to reduce the number of places in the code which the programmer must look through and investigate.
But let's return to PVS-Studio analyzer. Analysis of the whole code is complete and now you can start looking through the messages. By the way, if you have a multi-core processor analysis will be performed faster for all the cores will be used.
After getting a list of diagnostic warnings from the code analyzer, you can study it. Let's consider the first error:
Figure 8 - Detailed description of the error and the ways to correct it are given in MSDN
After correcting the used data types let's relaunch analysis. You will see that the number of diagnostic warnings is less in one. It means that the problem is corrected. In the same way you should deal with all the diagnostic warnings and correct those places in the code where there are possible problems.
Of course, in large real projects there will be not some tens of diagnostic warnings, but hundreds or even thousands of them. And looking through all of them is not a simple task. To simplify it PVS-Studio has several mechanisms. The first is filtration of warnings by the code of an error. The second is filtration by the content of the text of a diagnostic warning. The third is filtration by the paths to files. Let's consider the examples of using filtration systems.
Suppose you be sure that diagnostic messages with V112 code (using magic numbers) are not relevant to your application. In this case you may turn off showing of these diagnostic warnings with the help of the code analyzer's settings:
Figure 9 - Turning off some diagnostic warnings by the code
After that all the warnings with V112 code will disappear from the list of warnings. And you do not need to relaunch analysis for this. If you turn on these warnings they will appear in the list again without relaunching analysis.
Now let's consider another variant of filtration on the basis of the text of diagnostic warnings. Let's get back to PortSample example. One of the errors in this example is access to the array 'array' using an index of int type:
Figure 10 - Turning off some diagnostic warnings by the text
After that all the diagnostic warnings whose text contains the word 'array' will disappear from the list without relaunching the code analyzer. You can get them back by simply removing the word 'array' from the filter.
The last mechanism of reducing the number of diagnostic warnings is filtration on the basis of the paths to the project's files.
Suppose your project use Boost library. Of course, the analyzer will warn about potential problems in this library as well. But if you are sure that these warnings should not be considered you may simply add the path to the folder with Boost on ExcludeFromAnalysis page:
Figure 11 - Setting filtration of messages by files' names
After that the diagnostic warnings relating to the files in this folder will not be shown. This option requires relaunching the code analyzer.
There are also many other means to handle diagnostic warnings to be shown by setting the code analyzer but they lay beyond consideration in this document. We recommend that you refer to the documentation on the code analyzer's settings.
Having looked through all the warnings shown by the code analyzer you will find both real errors in programs and constructions that are not errors. The point is that the analyzer cannot detect all the errors in programs 100% accurately without the so called "false responses". Only the programmer who knows and understands the program can determine if there is an error in a particular place. The code analyzer can only significantly reduce the number of sections which must be looked through by the developer.
Thus, of course, there is no sense in trying to correct all the potential problems detected by the code analyzer.
But you should try to correct as many code sections as you can. It is especially relevant when the static analyzer is used not once just to verify an application when, for example, porting it on a 64-bit system, but regularly with the purpose to detect new errors and insufficient constructions. In this case correction of sections which are actually not errors, and also setting of the analyzer to suppress some types of errors will allow you to significantly save on time when using the analyzer next time.
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