qac

This chapters describes how QAC is supported by TUTTI. As QAC is a static analysis tool, it is supported with a compiler wrapper and a result scanner like splint (which is also a static analysis tool). QAC allows to analyze the source code without execution of this code. Hence it can be applied in the early stage of development.

qac_compiler

qac_compiler is a wrapper for QAC static analysis tool. It as the same interface as the gnu compiler collection (gcc). The compiler wrapper will compile the source code using the parameters specified at command line. It will also invoke QAC to analyze the source code. This results in annotated source code files with extension .qac. The annotated source file contain warnings that QAC has issued.

Language subsetting

There are two warning subsets that can be applied by qac_compiler. These language subsets represent the two different programming standard (i.e. the ABSOLUTE programming standard and the RELATIVE programming standard.

Absolute programming standard

The absolute programming standards is a warning subset which excludes erroneous constructions in the C programming language. QAC warnings resulting from this warning subset must always be solved as they represent real errors. The absolute programming standards applied to ALL code.

Relative programming standard

The relative programming standards is a warning subset which excludes erroneous as well as dangerous constructions in the C programming language. QAC warnings resulting from this warning subset must always be solved as they represent problems with respect to run-time behavior or maintenance aspects. The relative programming standards is more strict than the absolute standard and must be applied to NEWLY developed code of WDS. By default the absolute programming standard is employed by qac_compiler.

Employing the relative programming standards

The behavior of the qac_compiler script can be influenced by comment lines in the code. By adding /* QAC APPLY RELATIVE */ in the source code, the relative programming standard will be in effect will analyzing that specific compilation unit (i.e. source code file). This is demonstrated below:

/*
 *
 * blab bla
 *
 * QAC APPLY RELATIVE
 *
 */

It does not matter where the ``QAC APPLY RELATIVE'' tag is located as long it is somewhere in the code.

Suppression tags

It is important that warnings which can be ignored according to the author of the code are suppressed. This can be achieved by adding a comment with a suppression tag. A suppression tag is a specific comment which is placed above the line resulting in the qac warning. This is demonstrated by the next example:

/*
 *
 * Piece of code that has a fall through that must be suppressed
 *
 * QAC APPLY RELATIVE
 *
 */
      void jump( int location )
      {
        switch( location )
        {
            case 2:
            {
                printf("bye ");
            }
            /* fall through, QAC EXPECT 2003 */
            case 1:     
            {
                printf("bye ");
                break;
            }
            default:
            {
                printf("ERROR);
                break;
            }
        }

The regular expression of a QAC suppression tag is as follows :

".*\/*QAC\ *EXPECT\ *<nr_1>\ *((,\ *<nr_2>\ *)+)?\*\/"

Analyzing the results

The results of the QAC analysis are recorded in the .qac files. These files can be analyzed using the qac_scan script. See qac_scan(1).

qac_scan

qac_scan is a script which reads the annotated .qac files resulting from a static analysis with qac_compiler. The warnings are extracted and suppressions annotated in the source will be effectuated. Warnings which occur in the .qac file and that are not suppressed will be issued to the stdout device.

Arguments

Normally, the output format of qac_scan is he same as the gcc compiler collection. This format is $<$file$>$,$<$line$>$,$<$message$>$. This allows the programming to parse the output by an editor. It is also possible to generate output in HTML output. Add -html as an optional argument for this purpose.