= CppCheck Static Analysis using Compile Commands
:toc:
:toc-placement!:

toc::[]

# Introduction

This example shows how to call the
https://clang-analyzer.llvm.org/[Clang Static Analyzer] to do static analysis using the
scan-build tool.

The files included in this example are:

```
$ tree
.
├── CMakeLists.txt
├── subproject1
│   ├── CMakeLists.txt
│   └── main1.cpp
└── subproject2
    ├── CMakeLists.txt
    └── main2.cpp
```

  * link:CMakeLists.txt[] - Top level CMakeLists.txt
  * link:subproject1/CMakeLists.txt[] - CMake commands for subproject 1
  * link:subproject1/main.cpp[] - source for a subproject with no errors
  * link:subproject2/CMakeLists.txt[] - CMake commands for subproject 2
  * link:subproject2/main2.cpp[] - source for a subproject that includes errors

# Requirements

To run this example you must have clang analyzer and the scan-build tool installed. This can be installed on Ubuntu using the following command.

[source,bash]
----
$ sudo apt-get install clang
----

It will result in the tool being available as:

[source,bash]
----
$ scan-build-3.6
----

# Concepts

## scan-build

To run clang static analyzer you can use the tool `scan-build` to run the analyzer when you
also run the compiler. This overrides the CC and CXX environment variables and replaces them with it's own tools. To run it you can do

[source,bash]
----
$ scan-build-3.6 cmake ..
$ scan-build-3.6 make
----

By default this will run the standard compiler for your platform, i.e. `gcc` on linux. However, if you want to override this you can change the command to:

[source,bash]
----
$ scan-build-3.6 --use-cc=clang-3.6 --use-c++=clang++-3.6 -o ./scanbuildout/ make
----

## scan-build output

scan-build will only output warnings during compile time and will also generate a list of HTML files which contain detailed analysis of the error.

[source,bash]
----
$ cd scanbuildout/
$ tree
.
└── 2017-07-03-213514-3653-1
    ├── index.html
    ├── report-42eba1.html
    ├── scanview.css
    └── sorttable.js

1 directory, 4 files
----

By default these are output to +/tmp/scanbuildout/{run folder}+. You can change this using `scan-build -o /output/folder`.

# Building the example

[source,bash]
----
$ mkdir build

$ cd build/

$ scan-build-3.6 -o ./scanbuildout make
scan-build: Using '/usr/lib/llvm-3.6/bin/clang' for static analysis
make: *** No targets specified and no makefile found.  Stop.
scan-build: Removing directory '/data/code/clang-analyzer/build/scanbuildout/2017-07-03-211632-937-1' because it contains no reports.
scan-build: No bugs found.
devuser@91457fbfa423:/data/code/clang-analyzer/build$ scan-build-3.6 -o ./scanbuildout cmake ..
scan-build: Using '/usr/lib/llvm-3.6/bin/clang' for static analysis
-- The C compiler identification is GNU 5.4.0
-- The CXX compiler identification is GNU 5.4.0
-- Check for working C compiler: /usr/share/clang/scan-build-3.6/ccc-analyzer
-- Check for working C compiler: /usr/share/clang/scan-build-3.6/ccc-analyzer -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/share/clang/scan-build-3.6/c++-analyzer
-- Check for working CXX compiler: /usr/share/clang/scan-build-3.6/c++-analyzer -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found CPPCHECK: /usr/local/bin/cppcheck  
cppcheck found. Use cppccheck-analysis targets to run it
-- Configuring done
-- Generating done
-- Build files have been written to: /data/code/clang-analyzer/build
scan-build: Removing directory '/data/code/clang-analyzer/build/scanbuildout/2017-07-03-211641-941-1' because it contains no reports.
scan-build: No bugs found.

$ $ scan-build-3.6 -o ./scanbuildout make    
scan-build: Using '/usr/lib/llvm-3.6/bin/clang' for static analysis
Scanning dependencies of target subproject1
[ 25%] Building CXX object subproject1/CMakeFiles/subproject1.dir/main1.cpp.o
[ 50%] Linking CXX executable subproject1
[ 50%] Built target subproject1
Scanning dependencies of target subproject2
[ 75%] Building CXX object subproject2/CMakeFiles/subproject2.dir/main2.cpp.o
/data/code/clang-analyzer/subproject2/main2.cpp:7:17: warning: Dereference of null pointer (loaded from variable 'x')
   std::cout << *x << std::endl;
                ^~
1 warning generated.
[100%] Linking CXX executable subproject2
[100%] Built target subproject2
scan-build: 1 bug found.
scan-build: Run 'scan-view /data/code/clang-analyzer/build/scanbuildout/2017-07-03-211647-1172-1' to examine bug reports.

$ cd scanbuildout/
$ tree
.
└── 2017-07-03-213514-3653-1
    ├── index.html
    ├── report-42eba1.html
    ├── scanview.css
    └── sorttable.js

1 directory, 4 files
----