How to do code coverage with Gcovr tool

1. Prerequisites

Install Gcovr tool with sudo apt install gcovr

2. Sample code

$ cat hello.c
#include <stdio.h>

void print_hello()
{
	printf("Helloworld!!!");

	return;
}

int main()
{
	print_hello();

	return 0;
}

3. Compile source with --coverage or -fprofile-arcs -ftest-coverage flags

$ cc -fprofile-arcs -ftest-coverage hello.c -o hello

The .gcno record file is generated after adding the GCC compile option -ftest-coverage, which contains information for reconstructing the base block map and assigning source line numbers to blocks during the compilation process.

$ ls
total 32K
-rw-rw-r-- 1 shanmugk shanmugk 123 Dec 11 11:08 hello.c
-rw-rw-r-- 1 shanmugk shanmugk 608 Dec 11 11:08 hello.gcno
-rwxrwxr-x 1 shanmugk shanmugk 24K Dec 11 11:08 hello

4. Run the user program

Run the user program to generate the .gcda file that contains the coverage data counts.

$ ./hello 
Helloworld!!!

$ ls
total 36K
-rw-rw-r-- 1 shanmugk shanmugk 123 Dec 11 11:08 hello.c
-rw-rw-r-- 1 shanmugk shanmugk 608 Dec 11 11:08 hello.gcno
-rwxrwxr-x 1 shanmugk shanmugk 24K Dec 11 11:08 hello
-rw-rw-r-- 1 shanmugk shanmugk 120 Dec 11 11:08 hello.gcda

5. Run gcovr command to print a tabular report on the console

$ gcovr 
------------------------------------------------------------------------------
                           GCC Code Coverage Report
Directory: .
------------------------------------------------------------------------------
File                                       Lines    Exec  Cover   Missing
------------------------------------------------------------------------------
hello.c                                        6       6   100%   
------------------------------------------------------------------------------
TOTAL                                          6       6   100%
------------------------------------------------------------------------------

6. Generating HTML reports

$ gcovr --html-details coverage.html

$ ls
total 56K
-rw-rw-r-- 1 shanmugk shanmugk  123 Dec 11 11:08 hello.c
-rw-rw-r-- 1 shanmugk shanmugk  608 Dec 11 15:35 hello.gcno
-rwxrwxr-x 1 shanmugk shanmugk  24K Dec 11 15:35 hello
-rw-rw-r-- 1 shanmugk shanmugk  120 Dec 11 15:35 hello.gcda
-rw-rw-r-- 1 shanmugk shanmugk 7.7K Dec 11 15:51 coverage.html
-rw-rw-r-- 1 shanmugk shanmugk  10K Dec 11 15:51 coverage.hello.c.html

7. Open coverage.html file to browse the coverage report

$ firefox ./coverage.html