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David Lawrence authored
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.
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