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# Cppcheck 1.88 dev
## Introduction
Cppcheck is an analysis tool for C/C++ code. It provides unique code analysis to detect bugs and focuses on detecting undefined behaviour and dangerous coding constructs. The goal is to detect only real errors in the code (i.e. have very few false positives).
Supported code and platforms:
- You can check non-standard code that contains various compiler extensions, inline assembly code, etc.
- Cppcheck should be compilable by any C++ compiler that handles the latest C++ standard.
- Cppcheck should work on any platform that has sufficient CPU and memory.
Please understand that there are limits of Cppcheck. Cppcheck is rarely wrong about reported errors. But there are
many bugs that it doesn't detect.
You will find more bugs in your software by testing your software carefully, than by using Cppcheck. You will find
more bugs in your software by instrumenting your software, than by using Cppcheck. But Cppcheck can still detect some
of the bugs that you miss when testing and instrumenting your software.
## Getting started
### GUI
It is not required but creating a new project file is a good first step. There are a few options you can tweak to get
good results.
In the project settings dialog, the first option you see is "Import project". It is recommended that you use this
feature if you can. Cppcheck can import:
- Visual studio solution / project
- Compile database (can be generated from cmake/qbs/etc build files)
- Borland C++ Builder 6
When you have filled out the project settings and click on OK; the Cppcheck analysis will start.
### Command line
#### First test
Here is a simple code
int main()
{
char a[10];
a[10] = 0;
return 0;
}
If you save that into file1.c and execute:
cppcheck file1.c
The output from cppcheck will then be:
Checking file1.c...
[file1.c:4]: (error) Array 'a[10]' index 10 out of bounds
#### Checking all files in a folder
Normally a program has many source files. And you want to check them all. Cppcheck can check all source files in a directory:
cppcheck path
If "path" is a folder then cppcheck will recursively check all source files in this folder.
Checking path/file1.cpp...
1/2 files checked 50% done
Checking path/file2.cpp...
2/2 files checked 100% done
#### Check files manually or use project file
With Cppcheck you can check files manually, by specifying files/paths to check and settings. Or you can use a project file (cmake/visual studio/etc).
We don't know which approach (project file or manual configuration) will give you the best results. It is recommended that you try both. It is possible that you will get different results so that to find most bugs you need to use both approaches.
Later chapters will describe this in more detail.
#### Excluding a file or folder from checking
To exclude a file or folder, there are two options. The first option is to only provide the paths and files you want to check.
cppcheck src/a src/b
All files under src/a and src/b are then checked.
The second option is to use -i, with it you specify files/paths to ignore. With this command no files in src/c are checked:
cppcheck -isrc/c src
This option does not currently work with the `--project` option and is only valid when supplying an input directory. To ignore multiple directories supply the -i multiple times. The following command ignores both the src/b and src/c directories.
cppcheck -isrc/b -isrc/c
### Severities
The possible severities for messages are:
**error**
used when bugs are found
**warning**
suggestions about defensive programming to prevent bugs
**style**
stylistic issues related to code cleanup (unused functions, redundant code, constness, and such)
**performance**
Suggestions for making the code faster. These suggestions are only based on common knowledge. It is not certain you'll get any measurable difference in speed by fixing these messages.
**portability**
portability warnings. 64-bit portability. code might work different on different compilers. etc.
**information**
Configuration problems. The recommendation is to only enable these during configuration.
## Importing project
You can import some project files and build configurations into Cppcheck.
### Cppcheck GUI project
You can import and use Cppcheck GUI project files in the command line tool:
cppcheck --project=foobar.cppcheck
### CMake
Generate a compile database:
cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=ON .
The file `compile_commands.json` is created in the current folder. Now run Cppcheck like this:
cppcheck --project=compile_commands.json
### Visual Studio
You can run Cppcheck on individual project files (\*.vcxproj) or on a whole solution (\*.sln)
Running Cppcheck on an entire Visual Studio solution:
cppcheck --project=foobar.sln
Running Cppcheck on a Visual Studio project:
cppcheck --project=foobar.vcxproj
### C++ Builder 6
Running Cppcheck on a C++ Builder 6 project:
cppcheck --project=foobar.bpr
### Other
If you can generate a compile database then it's possible to import that in Cppcheck.
In Linux you can use for instance the `bear` (build ear) utility to generate a compile database from arbitrary build tools:
bear make
## Platform
You should use a platform configuration that match your target.
By default Cppcheck uses native platform configuration that works well if your code is compiled and executed locally.
Cppcheck has builtin configurations for unix and windows targets. You can easily use these with the --platform command line flag.
You can also create your own custom platform configuration in a xml file. Here is an example:
<?xml version="1"?>
<platform>
<char_bit>8</char_bit>
<default-sign>signed</default-sign>
<sizeof>
<short>2</short>
<int>4</int>
<long>4</long>
<long-long>8</long-long>
<float>4</float>
<double>8</double>
<long-double>12</long-double>
<pointer>4</pointer>
<size_t>4</size_t>
<wchar_t>2</wchar_t>
</sizeof>
</platform>
## Preprocessor Settings
If you use `--project` then Cppcheck will use the preprocessor settings from the imported project. Otherwise you'll probably want to configure the include paths, defines, etc.
### Defines
Here is a file that has 2 preprocessor configurations (with A defined and without A defined):
#ifdef A
x = y;
#else
x = z;
#endif
By default Cppcheck will check all preprocessor configurations (except those that have #error in them). So the above code will by default be analyzed both with `A` defined and without `A` defined.
You can use `-D` to change this. When you use `-D`, cppcheck will by default only check the given configuration and nothing else. This is how compilers work. But you can use `--force` or `--max-configs` to override the number of configurations.
Check all configurations:
cppcheck file.c
Only check the configuration A:
cppcheck -DA file.c
Check all configurations when macro A is defined
cppcheck -DA --force file.c
Another useful flag might be `-U`. It tells Cppcheck that a macro is not defined. Example usage:
cppcheck -UX file.c
That will mean that X is not defined. Cppcheck will not check what happens when X is defined.
### Include paths
To add an include path, use `-I`, followed by the path.
Cppcheck's preprocessor basically handles includes like any other preprocessor. However, while other preprocessors stop working when they encounter a missing header, cppcheck will just print an information message and continues parsing the code.
The purpose of this behaviour is that cppcheck is meant to work without necessarily seeing the entire code. Actually, it is recommended to not give all include paths. While it is useful for cppcheck to see the declaration of a class when checking the implementation of its members, passing standard library headers is highly discouraged because it will result in worse results and longer checking time. For such cases, .cfg files (see below) are the better way to provide information about the implementation of functions and types to cppcheck.
## Suppressions
If you want to filter out certain errors you can suppress these.
Please note that if you see a false positive then we (the Cppcheck team) want that you report it so we can fix it.
### Plain text suppressions
You can suppress certain types of errors. The format for such a suppression is one of:
[error id]:[filename]:[line]
[error id]:[filename2]
[error id]
The `error id` is the id that you want to suppress. The easiest way to get it is to use the --template=gcc command line flag. The id is shown in brackets.
The filename may include the wildcard characters \* or ?, which match any sequence of characters or any single character respectively. It is recommended that you use "/" as path separator on all operating systems.
### Command line suppression
The `--suppress=` command line option is used to specify suppressions on the command line. Example:
cppcheck --suppress=memleak:src/file1.cpp src/
### Suppressions in a file
You can create a suppressions file. Example:
// suppress memleak and exceptNew errors in the file src/file1.cpp
memleak:src/file1.cpp
exceptNew:src/file1.cpp
// suppress all uninitvar errors in all files
uninitvar
Note that you may add empty lines and comments in the suppressions file.
You can use the suppressions file like this:
cppcheck --suppressions-list=suppressions.txt src/
### XML suppressions
You can specify suppressions in a XML file. Example file:
<?xml version="1.0"?>
<suppressions>
<suppress>
<id>uninitvar</id>
<fileName>src/file1.c</fileName>
<lineNumber>10</lineNumber>
<symbolName>var</symbolName>
</suppress>
</suppressions>
The xml format is extensible and may be extended with further attributes in the future.
You can use the suppressions file like this:
cppcheck --suppress-xml=suppressions.xml src/
### Inline suppressions
Suppressions can also be added directly in the code by adding comments that contain special keywords. Before adding such comments, consider that the code readability is sacrificed a little.
This code will normally generate an error message:
void f() {
char arr[5];
arr[10] = 0;
}
The output is:
cppcheck test.c
[test.c:3]: (error) Array 'arr[5]' index 10 out of bounds
To suppress the error message, a comment can be added:
void f() {
char arr[5];
// cppcheck-suppress arrayIndexOutOfBounds
arr[10] = 0;
}
Now the `--inline-suppr` flag can be used to suppress the warning. No error is reported when invoking cppcheck this way:
cppcheck --inline-suppr test.c
You can specify that the inline suppression only applies to a specific symbol:
// cppcheck-suppress arrayIndexOutOfBounds symbolName=arr
You can write comments for the suppress, however is recommended to use ; or // to specify where they start:
// cppcheck-suppress arrayIndexOutOfBounds ; some comment
// cppcheck-suppress arrayIndexOutOfBounds // some comment
## XML output
Cppcheck can generate output in XML format. Use `--xml` to enable this format.
A sample command to check a file and output errors in the XML format:
cppcheck --xml file1.cpp
Here is a sample report:
<?xml version="1.0" encoding="UTF-8"?>
<results version="2">
<cppcheck version="1.66">
<errors>
<error id="someError" severity="error" msg="short error text"
verbose="long error text" inconclusive="true" cwe="312">
<location file0="file.c" file="file.h" line="1"/>
</error>
</errors>
</results>
### The `<error>` element
Each error is reported in a `<error>` element. Attributes:
**id**
id of error. These are always valid symbolnames.
**severity**
error/warning/style/performance/portability/information
**msg**
the error message in short format
**verbose**
the error message in long format
**inconclusive**
this attribute is only used when the error message is inconclusive
**cwe**
CWE ID for the problem. This attribute is only used when the CWE ID for the message is known.
### The `<location>` element
All locations related to an error are listed with `<location>` elements. The primary location is listed first.
Attributes:
**file**
filename. both relative and absolute paths are possible.
**file0**
name of the source file (optional)
**line**
line number
**info**
short information for each location (optional)
## Reformatting the text output
If you want to reformat the output so it looks different you can use templates.
### Predefined output formats
To get Visual Studio compatible output you can use --template=vs:
cppcheck --template=vs samples/arrayIndexOutOfBounds/bad.c
This output will look like this:
Checking samples/arrayIndexOutOfBounds/bad.c ...
samples/arrayIndexOutOfBounds/bad.c(6): error: Array 'a[2]' accessed at index 2, which is out of bounds.
To get gcc compatible output you can use --template=gcc:
cppcheck --template=gcc samples/arrayIndexOutOfBounds/bad.c
The output will look like this:
Checking samples/arrayIndexOutOfBounds/bad.c ...
samples/arrayIndexOutOfBounds/bad.c:6:6: warning: Array 'a[2]' accessed at index 2, which is out of bounds. [arrayIndexOutOfBounds]
a[2] = 0;
^
### User defined output format (single line)
You can write your own pattern. For instance, to get warning messages that are formatted like old gcc such format can be used:
cppcheck --template="{file}:{line}: {severity}: {message}" samples/arrayIndexOutOfBounds/bad.c
The output will look like this:
Checking samples/arrayIndexOutOfBounds/bad.c ...
samples/arrayIndexOutOfBounds/bad.c:6: error: Array 'a[2]' accessed at index 2, which is out of bounds.
A comma separated format:
cppcheck --template="{file},{line},{severity},{id},{message}" samples/arrayIndexOutOfBounds/bad.c
The output will look like this:
Checking samples/arrayIndexOutOfBounds/bad.c ...
samples/arrayIndexOutOfBounds/bad.c,6,error,arrayIndexOutOfBounds,Array 'a[2]' accessed at index 2, which is out of bounds.
### User defined output format (multi line)
Many warnings have multiple locations. Example code:
void f(int *p)
{
*p = 3; // line 3
}
int main()
{
int *p = 0; // line 8
f(p); // line 9
return 0;
}
There is a possible null pointer dereference at line 3. Cppcheck can show how it came to that conclusion by showing extra location information. You need to use both --template and --template-location at the command line.
Example command:
cppcheck --template="{file}:{line}: {severity}: {message}\n{code}" --template-location="{file}:{line}: note: {info}\n{code}" multiline.c
The output from Cppcheck is:
Checking multiline.c ...
multiline.c:3: warning: Possible null pointer dereference: p
*p = 3;
^
multiline.c:8: note: Assignment 'p=0', assigned value is 0
int *p = 0;
^
multiline.c:9: note: Calling function 'f', 1st argument 'p' value is 0
f(p);
^
multiline.c:3: note: Null pointer dereference
*p = 3;
^
The first line in the warning is formatted by the --template format.
The other lines in the warning are formatted by the --template-location format.
#### Format specifiers for --template
The available specifiers for --template are:
**{file}**
File name
**{line}**
Line number
**{column}**
Column number
**{callstack}**
Write all locations. Each location is written in [{file}:{line}] format and the locations are separated by ->. For instance it might look like: [multiline.c:8] -> [multiline.c:9] -> [multiline.c:3]
**{inconclusive:text}**
If warning is inconclusive then the given text is written. The given text can be any arbitrary text that does not contain }. Example: {inconclusive:inconclusive,}
**{severity}**
error/warning/style/performance/portability/information
**{message}**
The warning message
**{id}**
Warning id
**{code}**
The real code.
**\t**
Tab
**\n**
Newline
**\r**
Carriage return
#### Format specifiers for --template-location
The available specifiers for `--template-location` are:
**{file}**
File name
**{line}**
Line number
**{column}**
Column number
**{info}**
Information message about current location
**{code}**
The real code.
**\t**
Tab
**\t**
Newline
**\r**
Carriage return
## Speeding up Cppcheck
It is possible to speed up Cppcheck analysis in a few different ways.
### Preprocessor configurations
Imagine this source code:
void foo()
{
int x;
#ifdef __GNUC__
x = 0;
#endif
#ifdef _MSC_VER
x = 1;
#endif
return x;
}
By default Cppcheck will try to check all the configurations. There are 3 important configurations here:
* Neither `__GNUC__` nor `_MSC_VER` is defined
* `__GNUC__` is defined
* `_MSC_VER` is defined
When you run Cppcheck, the output will be something like:
$ cppcheck test.c
Checking test.c ...
[test.c:10]: (error) Uninitialized variable: x
Checking test.c: __GNUC__...
Checking test.c: _MSC_VER...
Now if you want you can limit the analysis. You probably know what the target compiler is. If `-D` is supplied and you do not specify `--force` then Cppcheck will only check the configuration you give.
$ cppcheck -D __GNUC__ test.c
Checking test.c ...
Checking test.c: __GNUC__=1...
### Unused templates
If you think Cppcheck is slow and you are using templates, then you should try how it works to remove unused templates.
Imagine this code:
template <class T> struct Foo {
T x = 100;
};
template <class T> struct Bar {
T x = 200 / 0;
};
int main() {
Foo<int> foo;
return 0;
}
Cppcheck says:
$ cppcheck test.cpp
Checking test.cpp ...
[test.cpp:7]: (error) Division by zero.
It complains about division by zero in `Bar` even though `Bar` is not instantiated.
You can use the option `--remove-unused-templates` to remove unused templates from Cppcheck analysis.
Example:
$ cppcheck --remove-unused-templates test.cpp
Checking test.cpp ...
This lost message is in theory not critical, since `Bar` is not instantiated the division by zero should not occur in your real program.
The speedup you get can be remarkable.
### Check headers
TBD
## Misra
Cppcheck has an addon that checks for MISRA C 2012 compliance.
### Requirements
You need:
Python 2.X or 3.X
The MISRA C 2012 PDF. You can buy this from http://www.misra.org.uk (costs 15-20 pounds)
#### MISRA Text file
It is not allowed to publish the MISRA rule texts. Therefore the MISRA rule texts are not available directly in the addon. We can not publish the rule texts. Instead, you must provide the rule texts; the addon can read the rule texts from a text file. If you copy/paste all text in "Appendix A Summary of guidelines" from the MISRA pdf, then you have all the rule texts.
If you have installed xpdf, such text file can be generated on the command line (using pdftotext that is included in xpdf):
pdftotext misra-c-2012.pdf output.txt
The output might not be 100% perfect so you might need to make minor tweaks manually.
Other pdf-to-text utilities might work also.
To create the text file manually, copy paste Appendix A "Summary of guidelines" from the MISRA PDF. Format:
Appendix A Summary of guidelines
Rule 1.1
Rule text
Rule 1.2
Rule text
...
Rules that you want to disable does not need to have a rule text. Rules that don't have rule text will be suppressed by the addon.
## Library configuration
When external libraries are used, such as WinAPI, POSIX, gtk, Qt, etc, Cppcheck doesn't know how the external functions behave. Cppcheck then fails to detect various problems such as leaks, buffer overflows, possible null pointer dereferences, etc. But this can be fixed with configuration files.
Cppcheck already contains configurations for several libraries. They can be loaded as described below. Note that the configuration for the standard libraries of C and C++, std.cfg, is always loaded by cppcheck. If you create or update a configuration file for a popular library, we would appreciate if you upload it to us.
### Using your own custom .cfg file
You can create and use your own .cfg files for your projects. Use `--check-library` and `--enable=information` to get hints about what you should configure.
It is recommended that you use the `Library Editor` in the `Cppcheck GUI` to edit configuration files. It is available in the `View` menu. Not all settings are documented in this manual yet.
If you have a question about the .cfg file format it is recommended that you ask in the forum (<http://sourceforge.net/p/cppcheck/discussion/>).
The command line cppcheck will try to load custom .cfg files from the working path - execute cppcheck from the path where the .cfg files are.
The cppcheck GUI will try to load custom .cfg files from the project file path. The custom .cfg files should be shown in the Edit Project File dialog that you open from the `File` menu.
## HTML Report
You can convert the XML output from cppcheck into a HTML report. You'll need Python and the pygments module (http://pygments.org/) for this to work. In the Cppcheck source tree there is a folder htmlreport that contains a script that transforms a Cppcheck XML file into HTML output.
This command generates the help screen:
htmlreport/cppcheck-htmlreport -h
The output screen says:
Usage: cppcheck-htmlreport [options]
Options:
-h, --help show this help message and exit
--file=FILE The cppcheck xml output file to read defects from.
Default is reading from stdin.
--report-dir=REPORT_DIR
The directory where the html report content is written.
--source-dir=SOURCE_DIR
Base directory where source code files can be found.
An example usage:
./cppcheck gui/test.cpp --xml 2> err.xml
htmlreport/cppcheck-htmlreport --file=err.xml --report-dir=test1 --source-dir=.
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