lcov

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- README file for the LTP GCOV extension (LCOV) -
- Last changes: 2022-06-03 -
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Description
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LCOV is an extension of GCOV, a GNU tool which provides information about
what parts of a program are actually executed (i.e. "covered") while running
a particular test case. The extension consists of a set of Perl scripts
which build on the textual GCOV output to implement the following enhanced
functionality:

* HTML based output: coverage rates are additionally indicated using bar
graphs and specific colors.

* Support for large projects: overview pages allow quick browsing of
coverage data by providing three levels of detail: directory view,
file view and source code view.

LCOV was initially designed to support Linux kernel coverage measurements,
but works as well for coverage measurements on standard user space
applications.

Further README contents
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1. Included files
2. Installing LCOV
3. An example of how to access kernel coverage data
4. An example of how to access coverage data for a user space program
5. Questions and Comments

1. Important files
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README - This README file
CHANGES - List of changes between releases
bin/lcov - Tool for capturing LCOV coverage data
bin/genhtml - Tool for creating HTML output from LCOV data
bin/gendesc - Tool for creating description files as used by genhtml
bin/geninfo - Internal tool (creates LCOV data files)
bin/genpng - Internal tool (creates png overviews of source files)
bin/install.sh - Internal tool (takes care of un-/installing)
man - Directory containing man pages for included tools
example - Directory containing an example to demonstrate LCOV
lcovrc - LCOV configuration file
Makefile - Makefile providing 'install' and 'uninstall' targets

2. Installing LCOV
------------------
The LCOV package is available as either RPM or tarball from:

https://github.com/linux-test-project/lcov/releases

To install the tarball, unpack it to a directory and run:

make install

Use Git for the most recent (but possibly unstable) version:

git clone https://github.com/linux-test-project/lcov.git

Change to the resulting lcov directory and type:

make install

3. An example of how to access Linux kernel coverage data
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Requirements: Follow the Linux kernel coverage setup instructions at:

https://docs.kernel.org/dev-tools/gcov.html

As root, do the following:

a) Resetting counters

lcov --zerocounters

b) Capturing the current coverage state to a file

lcov --capture --output-file kernel.info

c) Getting HTML output

genhtml kernel.info

Point the web browser of your choice to the resulting index.html file.

4. An example of how to access coverage data for a user space program
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Requirements: compile the program in question using GCC with the options
-fprofile-arcs and -ftest-coverage. During linking, make sure to specify
-lgcov or -coverage.

Assuming the compile directory is called "appdir", do the following:

a) Resetting counters

lcov --directory appdir --zerocounters

b) Capturing the current coverage state to a file

lcov --directory appdir --capture --output-file app.info

Note that this step only works after the application has
been started and stopped at least once. Otherwise lcov will
abort with an error mentioning that there are no data/.gcda files.

c) Getting HTML output

genhtml app.info

Point the web browser of your choice to the resulting index.html file.

Please note that independently of where the application is installed or
from which directory it is run, the --directory statement needs to
point to the directory in which the application was compiled.

For further information on the gcc profiling mechanism, please also
consult the gcov man page.

5. Questions and comments
-------------------------
See the included man pages for more information on how to use the LCOV tools.

In case of further questions, feel free to open a new issue using the issue
tracker on the LCOV code repository site at:

https://github.com/linux-test-project/lcov