Tools based around a modular C language frontend
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Sycek aims to provide tools based around a modular C language parser. Currently there's one tool 'ccheck', a C code style checker. It aims to support the HelenOS coding style for use with HelenOS and other projects. It can report and fix coding style issues. Sycek is available under an MIT-style license.


You need Linux or similar OS with a working compiler toolchain. Simply type:

$ make

Cross-compiling for HelenOS

You need a built HelenOS workspace and a working cross-compiler toolchain. If you don't have one, you need to do something like

$ git clone helenos
$ cd helenos
$ sudo tools/ amd64
$ make PROFILE=amd64

You may need to have some development packages installed. For details, see

Next you need to setup XCW tools which we use for the cross-compilation: $ PATH=$PATH:$PWD/tools/xcw/bin

Now go to your gzx workspace and off we go: $ cd ../gzx $ make test-hos

This will build the HelenOS binaries, install then to the HelenOS workspace and start emulation. Once in HelenOS start Ccheck by typing

# ccheck <arguments...>

If you want to only build the binaries without installing, type $ make hos

If you want to only build and install the binaries without starting emulation, type $ make install-hos

Now you need to go to root of your HelenOS workspace and type 'make' to re-build the OS image.


Ccheck runs as a pure parser in the sense it does not actually preprocess or compile the code. This means it does not recurse into the included files, thus there is no need for you to provide path to includes, defines or anything like that.

To check a single file and report issues, simply type:

$ ./ccheck <path-to-file>

to check a file, attempt to fix issues and report remaining issues, type:

$ ./ccheck --fix <path-to-file>

The original file will be saved as .orig

Ccheck returns an exit code of zero if it was able to parse the file successfully (regardles whether it found style issues), non-zero if it encountered a fatal error (e.g. was not able to properly parse the file)

An example output message from ccheck:

<test.h:43:28-30:int>: Expected whitespace after ','.

This means when checking the file test.h ccheck found a token int on line 43, columns 28-30. The int token was following a comma, but there was no space between the comma and the int. This a formatting issue that ccheck can fix automatically.

If an output line starts with Error:

Error: <./file_input.c:34:36:=> unexpected, expected '{' or ';'.

This means that ccheck failed to parse the file. On line 34, column 36 it expected a { or ;, but found a <= token. This means either that ccheck cannot parse this source file yet, or the file has incorrect syntax.

Accepted syntax

ccheck has a good understanding of the C language (C89, C99, C11, but not K & R). However for some particular syntax that is valid C but has bad style ccheck will fail with an Error instead of just reporting or fixing the style issue.

Examples of bad style that triggers a parse error include:

  • Gratuitous ; (e.g. empty declaration or null statement)
  • Empty statement as for loop iteration statement (ie. for(a;b;))
  • Any \ character outside of a preprocessor block
  • Gratuitous nested block
  • Any use of null statement (;) except as the body of a while loop or in the header of a for loop

Apart from standard C, ccheck also understands some compiler-specific extensions, such as

  • GCC inline assembler
  • GCC register ... asm(...) variable register assignment
  • GCC attribute syntax
  • GCC's __int128, __restrict__

ccheck also understands the C++ extern "C" declaration embedded in a header file.

Finally, ccheck supports some extensions to the C syntax that are exploited via the preprocessor. I.e., it understands certain specific uses of macros where the macros alter the language grammar. These are uses outside of e.g. function-like or accessor-like macros.

Examples of supported macro-based C syntax extensions include:

  • Symbolic variables or macros that expand to a string literal
  • Macros that take a type name (instead of an expression) as an argument
  • Loop macros
  • Macros that declare a global object
  • Macros that declare a struct or union member
  • Macros that stand as the header of a function definition
  • Symbolic variables used as a type specifier/qualifier
  • Symbolic variable or macro call used as attribute at the end of a global declaration header

Using ccheck for your project

It's easy to use ccheck if you are starting from scratch. Applying it to an existing codebase other than HelenOS is likely to require some, possibly non-trivial, changes to that code base before it would be fully parsable by ccheck.