TechVolve: Merging multiple coverage files using lcov

In my earlier posts How to - gcov/lcov for linux user space process and How to - gcov/lcov for linux kernel modules, I covered how to get a code coverage report for user space applications and kernel modules. In this post, I will provide a quick tip for merging multiple coverage files.

When do we need to merge coverage (*.gcda) files?

In High availability/Clustering environments, we get coverage information from multiple nodes. Sometimes, developers would like to combine coverage info from all the nodes & view the merged report rather than analyze multiple reports.

Steps to collect & merge coverage info

Lets take this sample program:

#include <stdio.h>

int main ( int argc, char *argv[] )
{
    if ( argc != 2 ) /* argc should be 2 for correct execution */
    {
        /* We print argv[0] assuming it is the program name */
        printf( "usage: %s test_num", argv[0] );
    }
    else
    {
        int i = atoi(argv[1]);

        if (i == 1)
                printf("Testcase 1\r\n");
        else
                printf("Testcase 2\r\n");
    }
}

I ran two tests on this sample program, collected gcda files & merged them using lcov:

root@babu-VirtualBox:~/gcov_tests/merge_tests# ls

a.c

root@babu-VirtualBox:~/gcov_tests/merge_tests# gcc -fprofile-arcs -ftest-coverage a.c

root@babu-VirtualBox:~/gcov_tests/merge_tests# ls

a.c a.gcno a.out

root@babu-VirtualBox:~/gcov_tests/merge_tests# ./a.out 1

Testcase 1

root@babu-VirtualBox:~/gcov_tests/merge_tests# ls

a.c a.gcda a.gcno a.out

root@babu-VirtualBox:~/gcov_tests/merge_tests# geninfo . -o ./coverage1.info

Found gcov version: 4.8.1

Scanning . for .gcda files ...

Found 1 data files in .

Processing a.gcda

Finished .info-file creation

root@babu-VirtualBox:~/gcov_tests/merge_tests# ls

a.c a.gcda a.gcno a.out coverage1.info

root@babu-VirtualBox:~/gcov_tests/merge_tests# rm a.gcda

root@babu-VirtualBox:~/gcov_tests/merge_tests# ./a.out 2

Testcase 2

root@babu-VirtualBox:~/gcov_tests/merge_tests# ls

a.c a.gcda a.gcno a.out coverage1.info

root@babu-VirtualBox:~/gcov_tests/merge_tests# geninfo . -o ./coverage2.info

Found gcov version: 4.8.1

Scanning . for .gcda files ...

Found 1 data files in .

Processing a.gcda

Finished .info-file creation

root@babu-VirtualBox:~/gcov_tests/merge_tests# ls

a.c a.gcda a.gcno a.out coverage1.info coverage2.info

root@babu-VirtualBox:~/gcov_tests/merge_tests# mkdir lcov_data

root@babu-VirtualBox:~/gcov_tests/merge_tests# lcov --add-tracefile coverage2.info -t test2 -a coverage1.info -t test1 -o coverage_merged.info

Combining tracefiles.

Reading tracefile coverage2.info

Reading tracefile coverage1.info

Writing data to coverage_merged.info

Overall coverage rate:

lines......: 87.5% (7 of 8 lines)

functions..: 100.0% (1 of 1 function)

branches...: 75.0% (3 of 4 branches)

root@babu-VirtualBox:~/gcov_tests/merge_tests# ls

a.c a.gcno coverage1.info coverage_merged.info lcov_data

a.gcda a.out coverage2.info

root@babu-VirtualBox:~/gcov_tests/merge_tests# genhtml -o ./lcov_data/ ./coverage_merged.info

Reading data file ./coverage_merged.info

Found 1 entries.

Found common filename prefix "/home/babu"

Writing .css and .png files.

Generating output.

Processing file gcov_tests/merge_tests/a.c

Writing directory view page.

Overall coverage rate:

lines......: 87.5% (7 of 8 lines)

functions..: 100.0% (1 of 1 function)

branches...: 75.0% (3 of 4 branches)

root@babu-VirtualBox:~/gcov_tests/merge_tests#

I hosted my code coverage results on my google drive - https://googledrive.com/host/0B4xkNcpT6ZbddzlPMHp3bEV3dk0/. Here is the screenshot that shows coverage for a.c: