问题
I'm trying to use lcov to generate coverage reports for my unit test suite, but I cannot even capture a tracefile. The error messages indicate that the source files cannot be found. The code is compiled by a Jenkins job on a build machine and the unit test are executed as a downstream job on a target machine. The source code and gcno files are transfered to the downstream job, which then executes the call to lcov. Here follows all the details, a cup of coffee might be needed.
On the build machine, make is executed in
/var/lib/jenkins/workspace/App-Coverage/BUILD/app/
The source code which I want coverage for is in subdirectories in
/var/lib/jenkins/workspace/App-Coverage/BUILD/app/packages/
The object files and gcno files are generated in an subdirectory o relative to the corresponding cpp file. So for example
/var/lib/jenkins/workspace/App-Coverage/BUILD/app/packages/subdir/Myclass.cpp
/var/lib/jenkins/workspace/App-Coverage/BUILD/app/packages/subdir/o/Myclass.o
/var/lib/jenkins/workspace/App-Coverage/BUILD/app/packages/subdir/o/Myclass.gcno
The source files and gcno files are copied to the unit test machine keeping the same folder structure and ends up in
/var/lib/jenkins/workspace/App-Coverage-Unittest/BUILD/app/
Note: There is a difference in the name of the workspace folder, "App-Coverage-Unittest" instead of "App-Coverage" since these two Jenkins jobs cannot have the same name.
So there is now for example
/var/lib/jenkins/workspace/App-Coverage-Unittest/BUILD/app/packages/subdir/Myclass.cpp
/var/lib/jenkins/workspace/App-Coverage-Unittest/BUILD/app/packages/subdir/o/Myclass.o
/var/lib/jenkins/workspace/App-Coverage-Unittest/BUILD/app/packages/subdir/o/Myclass.gcno
The unit tests are executed in
/opt/app/test/app
Using GCOV_PREFIX_STRIP and GCOV_PREFIX I make the gcda files appear in the same folders as the gcno files, so for example
/var/lib/jenkins/workspace/App-Coverage-Unittest/BUILD/app/packages/subdir/o/Myclass.gcno
/var/lib/jenkins/workspace/App-Coverage-Unittest/BUILD/app/packages/subdir/o/Myclass.gcda
Now I want to generate a coverage report using lcov, but I don't seem to understand how to set the paths correctly. The following examples where executed from /var/lib/jenkins/workspace/App-Coverage-Unittest/ by the Jenkins unittest job.
For example I tried
lcov -d BUILD/app/packages/ -c --no-external -o app.info -b /var/lib/jenkins/workspace/App-Coverage-Unittest/BUILD/app/
Reasoning: "-d BUILD/app/packages/" is what I want coverage for, "-b /var/lib/jenkins/workspace/App-Coverage-Unittest/BUILD/app/" is the root of my project in which I executed make (but on the build machine with a different workspace name...).
I also tried
lcov -d BUILD/app/packages/ --capture --no-external --output-file app.info
Reasoning : "-d BUILD/app/packages/" is what I want coverage for, don't set -b since relative path between each gcno/gcda and corresponding source file is the same as on the build machine, maybe lcov can figure it out.
In both cases get errors like "Cannot open source file /var/lib/jenkins/workspace/App-Coverage/BUILD/app/packages/subdir/Myclass.cpp" Note: The workspace folder in this path is that of the build machine, not the unittest machine. I thought that this is what the -b option is intended to solve. Clearly this is very suspicious and a valuable clue. I also get errors like "Cannot open source file ../../../packages/subdir/Myclass.h", which I guess has to do with how I include header files.
I have tried specifying all the paths here. Is it possible to generate the coverage report in the workspace of the unittest job using lcov, like I'm trying to do here? If yes, which are the correct paths to specify for lcov -d and -b flags? If not, what do I need to change to make it work?
回答1:
Fortunately the answer is yes, it is possible. I got a reply from an lcov dev providing me with the solution, thank you Peter!
He pointed out that all source code paths are hard-coded during the compile step into the .gcno files. However, despite not finding the source files (and producing the warnings) lcov will generate code coverage output even when the source code cannot be found, based solely on the data found in .gcda and .gcno files. However, the genhtml step will fail because it won't be able to find the source code to annotate with code coverage data.
The solution is to use lcov's "geninfo_adjust_src_path" configuration setting. By using this setting, lcov is instructed to change source code paths as found in the .gcno files into the correct source code paths while writing the output .info files. So in my case:
lcov -d BUILD/app/packages/ --capture --no-external --output-file app.info
--rc geninfo_adjust_src_path="/var/lib/jenkins/workspace/App-Coverage/BUILD/
=> /var/lib/jenkins/workspace/App-Coverage-Unittest/BUILD/"
The warnings "Cannot open source file" will still be there when invoking lcov, but the resulting .info file will contain the correct paths and can therefore be converted to HTML on the test machine using genhtml.
来源：https://stackoverflow.com/questions/40642912/cannot-generate-coverage-report-using-lcov