Finally integrating Gcov and Lcov tool into Cppagent build process

This is most probably my final task on Implementing Code Coverage Analysis for Mtconnect Cppagent. In my last post i showed you the how the executable files are generated using Makefiles. In Cppagent the Makefiles are actually autogenerated by a cross-platform Makefile generator tool CMakeTo integrate Gcov and Lcov into the build system we actually need to start from the very beginning of the process which is cmake. The CMake commands are written in CmakeLists.txt files. A minimal cmake file could look something like this. Here we have the test_srcs as the source file and agent_test as the executable.

cmake_minimum_required (VERSION 2.6)


set(test_srcs menu.cpp)

add_executable(agent_test ${test_srcs})

Now lets expand and understand the CMakeLists.txt for cppagent.


This sets the path where cmake should look for files when files or include_directories command is used. The set command is used to set values to the variables. You can print all the available variable out using the following code.

get_cmake_property(_variableNames VARIABLES)
foreach (_variableName ${_variableNames})
    message(STATUS "${_variableName}=${${_variableName}}")


Next section of the file:

 set(LibXML2_INCLUDE_DIRS ../win32/libxml2-2.9/include )
 set(bits 64)
 set(bits 32)
 file(GLOB LibXML2_LIBRARIES "../win32/libxml2-2.9/lib/libxml2_a_v120_${bits}.lib")
 file(GLOB LibXML2_DEBUG_LIBRARIES ../win32/libxml2-2.9/lib/libxml2d_a_v120_${bits}.lib)
 set(CPPUNIT_INCLUDE_DIR ../win32/cppunit-1.12.1/include)
 file(GLOB CPPUNIT_LIBRARY ../win32/cppunit-1.12.1/lib/cppunitd_v120_a.lib)

Here, we are checking the platform we are working on and accordingly the library variables are being set to the windows based libraries. We will discuss the file command later.

 set(LINUX_LIBRARIES pthread)

Next if the OS platform is Unix based then we execute the command uname as child-process and store the output in CMAKE_SYSTEM_NAME variable. If its a Linux environment., Linux  will be stored in the CMAKE_SYSTEM_NAME variable, hence,  we set the variable LINUX_LIBRARIES to pthread(which is the threading library for linux). Now we find something similar we did in our test CMakeLists.txt. The project command sets the project name, version etc. The next line stores the source file paths to a variable test_src

set( test_srcs file1 file2 ...)
Now we will discuss about the next few lines.
file(GLOB test_headers *.hpp ../agent/*.hpp)

The file command is used to manipulate the files. You can read, write, append files, also GLOB allows globbing of files which is used to generate a list of files matching the expression you give. So here wildcard expression is used to generate a list of all header files in the particular folder *.hpp.

include_directories(../lib ../agent .)

This command basically tells cmake to add the directories specified by it to its list of directories when looking for a file.

find_package(CppUnit REQUIRED)

This command looks for package and loads the settings from it. REQUIRED makes sure the External package is loaded properly else it must stop throwing an error.


add_definitions is where the additional compile time flags are added.

add_executable(agent_test ${test_srcs} ${test_headers})

This line generates an executable target for the project named agent_test and test_src and test_headers are its source and header files respectively. 

target_link_libraries(agent_test ${LibXML2_LIBRARIES} ${CPPUNIT_LIBRARY} ${LINUX_LIBRARIES})

This line links the executable its libraries.

::Gcov & Lcov Integration::

Now that we know our CMake file well, lets make the necessary changes.

Step #1

Add two variables and set the appropriate compile and linking flags for gcov and lcov respectively.

set(GCOV_COMPILE_FLAGS "-fprofile-arcs -ftest-coverage")
set(GCOV_LINK_FLAGS "-lgcov")

Step #2

Split the source into two halves one being the unit test source files and the other being the cppagent source files. We are not interested in unit test files’ code coverage.

set( test_srcs test.cpp
set(agent_srcs ../agent/adapter.cpp 

Step #3

Like i told in Step 2 we are not interested in unit test source files. So here we just add the Gcov compile flags to only the cppagent source files. So .gcno files of only the agent source files are generated.


Step #4

Now we also know that for coverage analysis we need to link the “lgcov” library. Therefore, we do this in the following way.

target_link_libraries(agent_test ${LibXML2_LIBRARIES} ${CPPUNIT_LIBRARY} ${LINUX_LIBRARIES} ${GCOV_LINK_FLAGS}) 

Step #5

Since we love things to be automated. I added a target for the make command to automate the whole process of running test and copying the “.gcno” files and moving the “.gcda” files to a folder then running the lcov command to read the files and prepare a easily readable statistics and finally the genhtml command to generate the html output. add_custom_target allows you to add custom target for make(Here i added “cov” as the target name). COMMAND allows you to specify simple bash commands.

add_custom_target( cov
COMMAND [ -d Coverage ]&&rm -rf Coverage/||echo "No folder"
COMMAND mkdir Coverage
COMMAND agent_test
COMMAND cp CMakeFiles/agent_test.dir/__/agent/*.gcno Coverage/
COMMAND mv CMakeFiles/agent_test.dir/__/agent/*.gcda Coverage/
COMMAND cd Coverage&&lcov -t "result" -o -c -d .
COMMAND cd Coverage&&genhtml -o coverage
COMMENT "Generated Coverage Report Successfully!"


Now to build test and generate report.

Step #1 cmake .    // In project root which cppagent/
Step #2 cd test    // since we want to build only test
Step #3 make       // This will build the agent_test executable.
Step #4 make cov   // Runs test, Copies all files to Coverage folder, generates report.

So, we just need to open the Coverage/coverage/index.html to view the analysis report. Final file will look something like this.

Finally integrating Gcov and Lcov tool into Cppagent build process

Using Gcov and Lcov to generate Test Coverage Stats for Cppagent

In my last post we generated Code coverage statistics for a sample c++. In this post i will be using gcov & lcov to generate similar code coverage for tests in cppagent. To use gcov we first need to compile the source files with --coverage flag. Our sample c++ program was a single file so it was easy to compile, but for cppagent they use makefiles to build the project. Hence, i started with the Makefile looking for the build instructions.

If my previous posts i discussed the steps for building the agent_test executable, which starts by running make command in test folder. So i started tracing the build steps from the Makefile in test folder. Since we run make without any parameters, the default target is going to be executed.

The first few lines of the file were as below.

# Default target executed when no arguments are given to make.

default_target: all

.PHONY : default_target

These lines specifies that the default_target for this build is all. On moving down the file we see the rules for all.

# The main all target

all: cmake_check_build_system

cd /home/subho/work/github/cppagent_new/cppagent && $(CMAKE_COMMAND) -E cmake_progress_start /home/subho/work/github/cppagent_new/cppagent/CMakeFiles /home/subho/work/github/cppagent_new/cppagent/test/CMakeFiles/progress.marks

cd /home/subho/work/github/cppagent_new/cppagent && $(MAKE) -f CMakeFiles/Makefile2 test/all

$(CMAKE_COMMAND) -E cmake_progress_start /home/subho/work/github/cppagent_new/cppagent/CMakeFiles 0

.PHONY : all

So here in the line

cd /home/subho/work/github/cppagent_new/cppagent && $(MAKE) -f CMakeFiles/Makefile2 test/all

We can see Makefile2 is invoked with target test/all.

In Makefile2 towards the end of the file we can see the test/all target build instructions as,

# Directory level rules for directory test

# Convenience name for "all" pass in the directory.

test/all: test/CMakeFiles/agent_test.dir/all

.PHONY : test/all

The rule says to run the commands defined under target test/CMakeFiles/agent_test.dir/all. These commands are:


$(MAKE) -f test/CMakeFiles/agent_test.dir/build.make test/CMakeFiles/agent_test.dir/depend

$(MAKE) -f test/CMakeFiles/agent_test.dir/build.make test/CMakeFiles/agent_test.dir/build

$(CMAKE_COMMAND) -E cmake_progress_report /home/subho/work/github/cppagent_new/cppagent/CMakeFiles 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58

@echo "Built target agent_test"

.PHONY : test/CMakeFiles/agent_test.dir/all

The first two lines run the build.make file with target ‘test/CMakeFiles/agent_test.dir/depend‘ and ‘test/CMakeFiles/agent_test.dir/build‘ . The build.make contains all the compile instructions for each of the c++ files. This file is in ‘test/CMakeFiles/agent_test.dir’ folder along with flag.make , link.txt etc files. The  flag.make file contains all the compile flags and the ‘link.txt‘ contains the libraries flag needed by linker. On adding the --coverage flag to these files we can make the c++ source files compile with gcov linked hence .gcno files are generated when the make command is run.

After that we need to run the agent_test as usual. This will create the data files .gcda files. After that we need to gather the .gcda and .gcno files together and run the lcov and genhtml commands and then the html output will be obtained.

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Using Gcov and Lcov to generate Test Coverage Stats for Cppagent