C PROGRAMMING

# Commenting And Documentation

## General Tips

• Always use \ style comments where possible. This allows you to use /* style comments for commenting out large blocks of code when debugging. If you want to comment a block of code which has /* comments inside it, you will run into problems! (unfortunately, */ style comments don’t nest in c).
• However, sometimes you still need to comment out blocks of code which have /* comments already inside them (maybe your using someone else’s code?). To do this, you can use the preprocessor trick #if 0 (see code below).
// This is a single lined comment, and the preferred way of doing things

/* This is
a multilined
comment.
And should be used sparingly as these don't nest */

// The following example shows how you can comment out code blocks
// containing "/*" comments using the pre-processor and "#if 0"
#if 0
void test1()
{
/* Annoying multi-line
comment in a block
of code you want to comment */
}
#endif // #if 0

## C Supports URL’s, Wait What?

Did you know that:

http://www.google.com

is valid syntax in C? Wait, what? O.K., I was lying, C doesn’t support URL’s, but the syntax is still valid! What it actually represents is a label (http:), followed by a single-line comment (//www.google.com).

## Commenting Styles

Some people put function descriptions after the function name and parameters, and before the opening curly brace (for example, some windows driver files). I find this method weird and hard to read.

NTSTATUS
DriverEntry(
IN PDRIVER_OBJECT  DriverObject,
IN PUNICODE_STRING RegistryPath
)
/*++

Routine Description:

Installable driver initialization entry point.
This entry point is called directly by the I/O system.

Arguments:

DriverObject - pointer to the driver object

RegistryPath - pointer to a unicode string representing the path,
to driver-specific key in the registry.

Return Value:

STATUS_SUCCESS if successful,
STATUS_UNSUCCESSFUL otherwise.

--*/
{
WDF_DRIVER_CONFIG               config;
NTSTATUS                        status;

rest of function code...

## Doxygen

Doxygen is a powerful documentation generator that can be used with the C language. For more information and code examples with Doxygen, go to the Doxygen page.