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27-Apr-2000 |
David Lawrence <source@isc.org> |
Vertical whitespace is encouraged for improved code legibility by
grouping closely related statements and then separating them with a
single empty line.
Lines should not be longer than 79 characters, even if it requires
violating the indentation rules to do so. Since ANSI is assumed, the
best way to deal with strings that extend past column 79 is to break
them into two or more sections separated from each other by a newline
and indentation. (w/example)
Note that <isc/lang.h> should be included by any public
header file to get the ISC_LANG_BEGINDECLS and ISC_LANG_ENDDECLS
macros used so the correct name-mangling happens for function
declarations when C++ programs include the file. <isc/lang.h> should
be included for private header files or for public files that do not
declare any functions. (w/example)
Fixed < and > use in sample header file.
The config.h file must never be included by any public header file.
The comma operator should not be used to form compound statements.
(w/example)
Generally speaking, when a control statement (<CODE>if, for</CODE> or
<CODE>while</CODE>) has only a single action associated with it, then no
bracing is used around the statement. Exceptions include when the
compiler would complain about an ambiguous else clause, or when extra
bracing improves the readability (a judgement call biased toward not
having the braces).
Do not put a space after the "sizeof" operator name, and also
parenthesize its argument, as in <CODE>malloc(4 * sizeof(long))</CODE>.
Do not put a space after a cast. (w/example)
<H4>The Ternary Operator</H4> (w/example)
The ?: operator should mostly be avoided. It is tolerated when
deciding what value to pass as a parameter to a function, such as
frequently happens with printf, and also when a simple (non-compound)
value is being used in assignment or as part of a calculation.
In particular, using the ternary operator to specify a return value is
verboten. (Well, Bob didn't tell me *forbidden* when he first said this
to me long ago, but I got the impression he really did not like it.)
Variables should not have their values assigned or changed when being
passed as parameters, except perhaps for the increment and decrement
operators. (This came up when I found something much like this in one
of our files:
malloc(size = 20);
All public interfaces to functions, macros, typedefs, and
variables provided by the library, should use names of the form
{library}_{module}_{what}, such as:
isc_buffer_t /* typedef */
dns_name_setbuffer(name, buffer) /* function */
ISC_LIST_HEAD(list) /* macro */
isc_commandline_argument /* variable */
however, structures which are typedef'd generally have the name of the
typedef sans the final _t:
struct dns_rbtnode {
/* ... members ... */
}
Generally speaking macros are defined with all capital letters, but
this is not universally consistent (eg, numerous isc_buffer_{foo}
macros).
The {module} and {what} segments of the name do not have underscores
separating natural word elements, as demonstrated in
isc_commandline_argument and dns_name_setbuffer above. The {module}
part is usually the same as the basename of the source file, but
sometimes other {module} interfaces appear within one file, such as
dns_label_* interfaces in lib/dns/name.c. However, in the public
libraries the file name must be the same as some module interface
provided by the file; e.g., dns_rbt_* interfaces would not be declared
in a file named redblack.c (in lieu of any other dns_redblack_*
interfaces in the file).
The one notable exception to this naming rule is the interfaces
provided by <isc/util.h>. There's a large caveat associated with the
public description of this file that it is hazardous to use because it
pollutes the general namespace.
<H4>Shared Private Interfaces</H4>
When a module provides an interface for internal use by other modules
in the library, it should use the same naming convention
described for the public interfaces, except {library} and {module}
are separated by a double-underscore. This indicates that the name is
internal, its API is not as formal as the public API, and thus it
might change without any sort of notice. |