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SCons support for gcc code coverage features

Project description

PyPi package version Travis CI build status https://ci.appveyor.com/api/projects/status/github/ptomulik/scons-tool-gcccov?svg=true

Support for gcc code coverage features. Note, this is not a tool for running gcov program.

Overview

gcc (and clang) is able to generate coverage info for gcov tool. You can use gcov to test code coverage in your programs. It helps discover where your optimization efforts will best affect your code.

gcov uses two files for profiling, see gcov files. The names of these files are derived from the original object file by substituting the file suffix with either .gcno, or .gcda. The .gcno notes file is generated when the source file is compiled. The .gcda count data file is generated when a program containing object files is executed. A separate .gcda file is created for each object file.

The purpose of scons-tool-gcccov is to help to incorporate the above gcov files into project’s dependency tree. Thanks to this, builders that depend on coverage data (for example gcov report builders or test runners) may be executed at right moments. This also helps to clean-up coverage data when the project gets cleaned up.

Installation

There are few ways to install this tool for your project.

From pypi

This method may be preferable if you build your project under a virtualenv. To add gcccov tool from pypi, type (within your wirtualenv):

pip install scons-tool-loader scons-tool-gcccov

or, if your project uses pipenv:

pipenv install --dev scons-tool-loader scons-tool-gcccov

Alternatively, you may add this to your Pipfile

[dev-packages]
scons-tool-loader = "*"
scons-tool-gcccov = "*"

The tool will be installed as a namespaced package sconstool.gcccov in project’s virtual environment. You may further use scons-tool-loader to load the tool.

As a git submodule

  1. Create new git repository:

    mkdir /tmp/prj && cd /tmp/prj
    touch README.rst
    git init
    
  2. Add the scons-tool-gcccov as a submodule:

    git submodule add git://github.com/ptomulik/scons-tool-gcccov.git site_scons/site_tools/gcccov
    
  3. For python 2.x create __init__.py in site_tools directory:

    touch site_scons/site_tools/__init__.py
    

    this will allow to directly import site_tools.gcccov (this may be required by other tools).

Other projects

  1. Download and copy this source tree to site_scons/site_tools/gcccov/ subdirectory of your project:

    mkdir -p site_scons/site_tools/gcccov && \
      (cd site_scons/site_tools/gcccov && \
        curl -L https://github.com/ptomulik/scons-tool-gcccov/tarball/master | \
        tar --strip-components=1 -xz)
    

Usage

Simple project with variant build and one shared library

  1. Create some source files, for example src/main.c and src/bar.c:

    // src/main.c
    extern int bar();
    int main(int argc, char *argv[])
    {
      return bar();
    }
    
    // src/bar.c
    int bar()
    {
      return 0;
    }
    
  2. Write the top level SConstruct file:

    # SConstruct
    env = Environment(tools = ['default', 'gcccov'])
    # Generate correct dependencies of `*.gcno' and `*.gcda' files on object
    # files being built from now on.
    env.GCovInjectObjectEmitters()
    env.Replace(CCFLAGS = ['-g', '-O0', '--coverage'], LINKFLAGS = ['--coverage'])
    SConscript('src/SConscript', variant_dir = 'build', duplicate = 0, exports = [ 'env' ])
    
  3. Write src/SConscript:

    # src/SConscript
    Import(['env'])
    bar = env.SharedLibrary(['bar'], ['bar.c'])
    pro = env.Program('main.c', LIBS = ['bar'], LIBPATH = ['.'])
    run = env.Action("LD_LIBRARY_PATH=%s %s" % (env.Dir('.').path, pro[0].path))
    env.Alias('check', pro, run)
    env.AlwaysBuild('check')
    
  4. Try it out, first we run pure build:

    ptomulik@barakus:$ scons -Q
    gcc -o build/bar.os -c -g -O0 --coverage -fPIC src/bar.c
    gcc -o build/libbar.so --coverage -shared build/bar.os
    gcc -o build/main.o -c -g -O0 --coverage src/main.c
    gcc -o build/main --coverage build/main.o -Lbuild -Lsrc -lbar
    

    Note the *.gcno files generated under build/ directory:

    ptomulik@barakus:$ ls build/*.gc*
    build/bar.gcno  build/main.gcno
    

    Now, cleanup project:

    ptomulik@barakus:$ scons -Q -c
    Removed build/bar.os
    Removed build/bar.gcno
    Removed build/libbar.so
    Removed build/main.o
    Removed build/main.gcno
    Removed build/main
    

    Note the *.gcno files get cleaned as well. Now we’ll build and run test program:

    ptomulik@barakus:$ scons -Q check
    gcc -o build/main.o -c -g -O0 --coverage src/main.c
    gcc -o build/bar.os -c -g -O0 --coverage -fPIC src/bar.c
    gcc -o build/libbar.so --coverage -shared build/bar.os
    gcc -o build/main --coverage build/main.o -Lbuild -Lsrc -lbar
    LD_LIBRARY_PATH=build build/main
    

    and list the coverage files again:

    ptomulik@barakus:$ ls build/*.gc*
    build/bar.gcda  build/bar.gcno  build/main.gcda  build/main.gcno
    

    Cleanup the project again:

    ptomulik@barakus:$ scons -Q -c
    Removed build/bar.os
    Removed build/bar.gcno
    Removed build/bar.gcda
    Removed build/libbar.so
    Removed build/main.o
    Removed build/main.gcno
    Removed build/main.gcda
    Removed build/main
    

    as you see, the *.gcda files get cleaned as well.

Integrating with cxxtest

In this example we create a simple test runner using cxxtest suite. To drive everything from SCons, we’ll use a scons-tool-cxxtest tool derived from the original SCons tool available in cxxtest repository.

  1. Install cxxtest framework:

    sudo apt-get install cxxtest
    
  2. Create new git repository:

    mkdir /tmp/prj && cd /tmp/prj
    touch README.rst
    git init
    
  3. Add scons-tool-gcccov as submodule:

    git submodule add git://github.com/ptomulik/scons-tool-gcccov.git site_scons/site_tools/gcccov
    
  4. Add scons-tool-cxxtest tool as submodule:

    git submodule add git://github.com/ptomulik/scons-tool-cxxtest.git site_scons/site_tools/cxxtest
    
  5. Create source file src/bar.cpp:

    // src/bar.cpp
    int bar()
    {
      return 0;
    }
    
  6. Create test file src/test.t.h

    // src/test.t.h
    #include <cxxtest/TestSuite.h>
    
    extern int bar();
    class BarTestSuite1 : public CxxTest::TestSuite
    {
    public:
        void testBar(void)
        {
            TS_ASSERT_EQUALS(bar(), 0);
        }
    };
    
  7. Write the top level SConstruct file:

    # SConstruct
    import os
    env = Environment(ENV = os.environ, tools = ['default', 'cxxtest', 'gcccov'])
    # Generate correct dependencies of `*.gcno' and `*.gcda' files on object
    # files being built from now on.
    env.GCovInjectObjectEmitters()
    env.Replace(CCFLAGS = ['-g', '-O0', '--coverage'], LINKFLAGS = ['--coverage'])
    SConscript('src/SConscript', variant_dir = 'build', duplicate = 0, exports = [ 'env' ])
    
  8. Write src/SConscript:

    # src/SConscript
    Import(['env'])
    bar = env.SharedLibrary(['bar'], ['bar.cpp'])
    env.CxxTest('test.t.h', LIBS = bar)
    
  9. Try it out:

    ptomulik@barakus:$ LD_LIBRARY_PATH=build scons -Q check
    Loading CxxTest tool...
    /usr/bin/python /usr/bin/cxxtestgen --runner=ErrorPrinter -o build/test.cpp src/test.t.h
    g++ -o build/test.o -c -g -O0 --coverage -I. build/test.cpp
    g++ -o build/bar.os -c -g -O0 --coverage -fPIC src/bar.cpp
    g++ -o build/libbar.so --coverage -shared build/bar.os
    g++ -o build/test --coverage build/test.o -Lbuild -Lsrc -lbar
    /tmp/prj/build/test
    Running cxxtest tests (1 test).OK!
    
  10. Check the gcov files created:

    ptomulik@barakus:$ ls build/*.gc*
    build/bar.gcda  build/bar.gcno  build/test.gcda  build/test.gcno
    
  11. Cleanup project:

    ptomulik@barakus:$ scons -Q -c
    Loading CxxTest tool...
    Removed build/bar.os
    Removed build/bar.gcno
    Removed build/bar.gcda
    Removed build/libbar.so
    Removed build/test.cpp
    Removed build/test.o
    Removed build/test.gcno
    Removed build/test.gcda
    Removed build/test
    

    As you see, all the generated gcov side effects are cleaned up as expected.

Finding out *.gcda files generated by a program run

If you need a list of *.gcda files generated when a program built with SCons is executed, you may use GCovFindGcdaNodes:

prog = env.Program('foo.c')
gcda = env.GCovFindGcdaNodes(prog[0])

This method is kinda dangerous and may break some builds. It internally scans for dependencies, and this is done at the time the SConscript file is processed. This may cause a problem with .sconsing file being written to wrong directory. More details are given in this thread.

As a conclusion I would say, that you should not use it in normal workflow. However, it may be handy for development, code maintenance and such. For these purposes I would suggest to add special CLI options or targets to your SCons script, to use it only when explicitly requested.

Module description

The scons-tool-gcccov tool provides three methods:

  • env.GCovInjectObjectEmitters(**overrides),
  • env.GCovFindGcdaNodes(root),
  • env.GCovGcdaGenerator(target, target_factory=_null, **overrides).

The first method, GCovInjectObjectEmitters is the only you’ll need in most projects. It injects special emitter to builders which create C/C++ object files such that their corresponding *.gcno and *.gcda files get added to dependency tree. The method should be invoked somewhere on the top of your SConstruct, before you specify first C/C++ file to be compiled. For example, this is incorrect:

# SConstruct
env.Program('foo')
env.GCovInjectObjectEmitters()

and this is correct:

# SConstruct
env.GCovInjectObjectEmitters()
env.Program('foo')

The remaining two methods should not be used in normal workflow. The GCovFindGcdaNodes determines what *.gcda files would be generated when running certain program(s) built with SCons. The GCovGcdaGenerator(alias) tells SCons that alias target generates these *.gcda files as a side effect (the alias should run a program/test runner and should have the program in its dependencies). The method should not be used currently, however, as it may break some builds, see this thread. Currently it’s here only for experiments.

Construction variables

The tool uses construction variables listed in the table below:

Option Description
GCCCOV_DISABLE Disable gcccov functionality.
GCCCOV_EXCLUDE Files (*.gcno, *.gcda, objects, etc.) to be excluded from processing.
GCCCOV_GCDA_SUFFIX Suffix for *.gcda files used by gcov dependency machinery.
GCCCOV_GCNO_SUFFIX Suffix for *.gcno files used by gcov dependency machinery.
GCCCOV_MAX_RECURSION Maximum recursion depth allowed when searching for *.gcda nodes.
GCCCOV_NOCLEAN List of gcov files which shouldn’t be Cleaned up.
GCCCOV_NOIGNORE List of gcov files which shouldn’t be Ignored from main target.
GCCCOV_RUNTEST_FACTORY Factory used to build runtest target (defaults to env.ans.Alias)
GCCCOV_RUNTEST_TARGETS List of targets (usually aliases) that run test runners.
GCCCOV_SOURCE_SUFFIXES List of source file suffixes for which dependency injector should be enabled.

GENERATING DOCUMENTATION

API DOCUMENTATION

You need few prerequisites to generate API documentation:

Install them with

sudo apt-get install python-epydoc python-docutils python-pygments

The API documentation may be generated with:

scons api-doc

The resultant html files get written to build/doc/api directory.

LICENSE

Copyright (c) 2014-2020 by Paweł Tomulik <ptomulik@meil.pw.edu.pl>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE

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