| ===================================== |
| Cross Translation Unit (CTU) Analysis |
| ===================================== |
| |
| Normally, static analysis works in the boundary of one translation unit (TU). |
| However, with additional steps and configuration we can enable the analysis to inline the definition of a function from another TU. |
| |
| .. contents:: |
| :local: |
| |
| Manual CTU Analysis |
| ------------------- |
| |
| Let's consider these source files in our minimal example: |
| |
| .. code-block:: cpp |
| |
| // main.cpp |
| int foo(); |
| |
| int main() { |
| return 3 / foo(); |
| } |
| |
| .. code-block:: cpp |
| |
| // foo.cpp |
| int foo() { |
| return 0; |
| } |
| |
| And a compilation database: |
| |
| .. code-block:: bash |
| |
| [ |
| { |
| "directory": "/path/to/your/project", |
| "command": "clang++ -c foo.cpp -o foo.o", |
| "file": "foo.cpp" |
| }, |
| { |
| "directory": "/path/to/your/project", |
| "command": "clang++ -c main.cpp -o main.o", |
| "file": "main.cpp" |
| } |
| ] |
| |
| We'd like to analyze `main.cpp` and discover the division by zero bug. |
| In order to be able to inline the definition of `foo` from `foo.cpp` first we have to generate the `AST` (or `PCH`) file of `foo.cpp`: |
| |
| .. code-block:: bash |
| |
| $ pwd $ /path/to/your/project |
| $ clang++ -emit-ast -o foo.cpp.ast foo.cpp |
| $ # Check that the .ast file is generated: |
| $ ls |
| compile_commands.json foo.cpp.ast foo.cpp main.cpp |
| $ |
| |
| The next step is to create a CTU index file which holds the `USR` name and location of external definitions in the source files: |
| |
| .. code-block:: bash |
| |
| $ clang-extdef-mapping -p . foo.cpp |
| c:@F@foo# /path/to/your/project/foo.cpp |
| $ clang-extdef-mapping -p . foo.cpp > externalDefMap.txt |
| |
| We have to modify `externalDefMap.txt` to contain the name of the `.ast` files instead of the source files: |
| |
| .. code-block:: bash |
| |
| $ sed -i -e "s/.cpp/.cpp.ast/g" externalDefMap.txt |
| |
| We still have to further modify the `externalDefMap.txt` file to contain relative paths: |
| |
| .. code-block:: bash |
| |
| $ sed -i -e "s|$(pwd)/||g" externalDefMap.txt |
| |
| Now everything is available for the CTU analysis. |
| We have to feed Clang with CTU specific extra arguments: |
| |
| .. code-block:: bash |
| |
| $ pwd |
| /path/to/your/project |
| $ clang++ --analyze -Xclang -analyzer-config -Xclang experimental-enable-naive-ctu-analysis=true -Xclang -analyzer-config -Xclang ctu-dir=. -Xclang -analyzer-output=plist-multi-file main.cpp |
| main.cpp:5:12: warning: Division by zero |
| return 3 / foo(); |
| ~~^~~~~~~ |
| 1 warning generated. |
| $ # The plist file with the result is generated. |
| $ ls |
| compile_commands.json externalDefMap.txt foo.ast foo.cpp foo.cpp.ast main.cpp main.plist |
| $ |
| |
| This manual procedure is error-prone and not scalable, therefore to analyze real projects it is recommended to use `CodeChecker` or `scan-build-py`. |
| |
| Automated CTU Analysis with CodeChecker |
| --------------------------------------- |
| The `CodeChecker <https://github.com/Ericsson/codechecker>`_ project fully supports automated CTU analysis with Clang. |
| Once we have set up the `PATH` environment variable and we activated the python `venv` then it is all it takes: |
| |
| .. code-block:: bash |
| |
| $ CodeChecker analyze --ctu compile_commands.json -o reports |
| [INFO 2019-07-16 17:21] - Pre-analysis started. |
| [INFO 2019-07-16 17:21] - Collecting data for ctu analysis. |
| [INFO 2019-07-16 17:21] - [1/2] foo.cpp |
| [INFO 2019-07-16 17:21] - [2/2] main.cpp |
| [INFO 2019-07-16 17:21] - Pre-analysis finished. |
| [INFO 2019-07-16 17:21] - Starting static analysis ... |
| [INFO 2019-07-16 17:21] - [1/2] clangsa analyzed foo.cpp successfully. |
| [INFO 2019-07-16 17:21] - [2/2] clangsa analyzed main.cpp successfully. |
| [INFO 2019-07-16 17:21] - ----==== Summary ====---- |
| [INFO 2019-07-16 17:21] - Successfully analyzed |
| [INFO 2019-07-16 17:21] - clangsa: 2 |
| [INFO 2019-07-16 17:21] - Total analyzed compilation commands: 2 |
| [INFO 2019-07-16 17:21] - ----=================---- |
| [INFO 2019-07-16 17:21] - Analysis finished. |
| [INFO 2019-07-16 17:21] - To view results in the terminal use the "CodeChecker parse" command. |
| [INFO 2019-07-16 17:21] - To store results use the "CodeChecker store" command. |
| [INFO 2019-07-16 17:21] - See --help and the user guide for further options about parsing and storing the reports. |
| [INFO 2019-07-16 17:21] - ----=================---- |
| [INFO 2019-07-16 17:21] - Analysis length: 0.659618854523 sec. |
| $ ls |
| compile_commands.json foo.cpp foo.cpp.ast main.cpp reports |
| $ tree reports |
| reports |
| ├── compile_cmd.json |
| ├── compiler_info.json |
| ├── foo.cpp_53f6fbf7ab7ec9931301524b551959e2.plist |
| ├── main.cpp_23db3d8df52ff0812e6e5a03071c8337.plist |
| ├── metadata.json |
| └── unique_compile_commands.json |
| |
| 0 directories, 6 files |
| $ |
| |
| The `plist` files contain the results of the analysis, which may be viewed with the regular analysis tools. |
| E.g. one may use `CodeChecker parse` to view the results in command line: |
| |
| .. code-block:: bash |
| |
| $ CodeChecker parse reports |
| [HIGH] /home/egbomrt/ctu_mini_raw_project/main.cpp:5:12: Division by zero [core.DivideZero] |
| return 3 / foo(); |
| ^ |
| |
| Found 1 defect(s) in main.cpp |
| |
| |
| ----==== Summary ====---- |
| ----------------------- |
| Filename | Report count |
| ----------------------- |
| main.cpp | 1 |
| ----------------------- |
| ----------------------- |
| Severity | Report count |
| ----------------------- |
| HIGH | 1 |
| ----------------------- |
| ----=================---- |
| Total number of reports: 1 |
| ----=================---- |
| |
| Or we can use `CodeChecker parse -e html` to export the results into HTML format: |
| |
| .. code-block:: bash |
| |
| $ CodeChecker parse -e html -o html_out reports |
| $ firefox html_out/index.html |
| |
| Automated CTU Analysis with scan-build-py (don't do it) |
| ------------------------------------------------------- |
| We actively develop CTU with CodeChecker as a "runner" script, `scan-build-py` is not actively developed for CTU. |
| `scan-build-py` has various errors and issues, expect it to work with the very basic projects only. |
| |
| Example usage of scan-build-py: |
| |
| .. code-block:: bash |
| |
| $ /your/path/to/llvm-project/clang/tools/scan-build-py/bin/analyze-build --ctu |
| analyze-build: Run 'scan-view /tmp/scan-build-2019-07-17-17-53-33-810365-7fqgWk' to examine bug reports. |
| $ /your/path/to/llvm-project/clang/tools/scan-view/bin/scan-view /tmp/scan-build-2019-07-17-17-53-33-810365-7fqgWk |
| Starting scan-view at: http://127.0.0.1:8181 |
| Use Ctrl-C to exit. |
| [6336:6431:0717/175357.633914:ERROR:browser_process_sub_thread.cc(209)] Waited 5 ms for network service |
| Opening in existing browser session. |
| ^C |
| $ |
