Gcov is a command-line tool that is used to test the code coverage of programs in Linux. It is a part of the GNU compiler collection (GCC) and is used to analyze the source code of C and C++ programs. Gcov works by instrumenting the object files generated by the compiler and creating a new executable file that collects data on the number of times each line of code is executed during program execution. This data can then be used to analyze how well the program is tested and to identify areas of the code that may need additional testing.
Overview
To use gcov, you must first compile your program with the -fprofile-arcs and -ftest-coverage options. These options tell the compiler to instrument the code and generate the necessary data files for gcov to use. Once your program is compiled, you can run it as you normally would, and gcov will collect data on the code coverage.
To generate a report on the code coverage, you can use the gcov command followed by the name of the source file. This will generate a coverage report for each function in the file, showing the number of times each line of code was executed during program execution. For example, to generate a report for the file main.c, you would run the following command:
gcov main.c
This will generate a file named main.c.gcov that contains the coverage report. You can then view this report using a text editor or a tool like the GNU Emacs text editor.
Gcov can also be used to generate coverage reports for multiple source files at once. To do this, you can use the wildcard character (*) to specify the files you want to include in the report. For example, to generate a report for all the source files in the current directory, you would run the following command:
gcov *.c
This will generate a coverage report for each source file in the directory.
Options
The following options are available for use with the gcov command:
| Option | Description |
|---|---|
| -b | Generate branch coverage information |
| -c | Generate coverage information for each source file |
| -f | Generate function coverage information |
| -n | Do not generate output for files with no coverage |
| -o dir | Place output files in the specified directory |
| -p | Preserve timestamps on output files |
| -r | Generate coverage information for all files in the directory tree |
| -s | Generate summary information |
Troubleshooting tips
If you encounter issues when using gcov, there are a few things you can try to troubleshoot the problem:
- Make sure that you have compiled your program with the -fprofile-arcs and -ftest-coverage options.
- Check that the object files generated by the compiler are being instrumented correctly by running the nm command on the object file and looking for the __gcov_* symbols.
- Ensure that you have permission to write to the directory where the output files will be generated.
- If you are using gcov with a shared library, make sure that the library is compiled with the -fprofile-arcs and -ftest-coverage options as well.
Notes
- Gcov only works with C and C++ programs.
- Gcov is only available on Linux systems that have GCC installed.
- Gcov can be used in conjunction with other testing tools, such as the GNU Autotest framework, to automate the testing process.