1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
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
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
|
=====================================
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
$
|
