STYLE

@@ -1,11 +1,51 @@
+“Everyone knows that debugging is twice as hard as writing a program in the
+first place. So if you’re as clever as you can be when you write it, how
+will you ever debug it?”
+	– Brian Kernighan, The Elements of Programming Style
+
+
 The following guidelines are conducive to clear and readable code that is
 consistent with the style of the rest of the Bonsai Computer System.
 
-0. Braces are mandatory for all control flow.
 
-1. Nested indentation should be kept to a minimum.
+Use
+===
 
-2. Empty lines should be placed between different kinds of statements:
+ 0. A single line for control flow statements short enough to be easily
+ understood at a glance:
+
+	if !(argc < 0) { usage(program_name); }
+
+ This applies to C switch statements and cases and Rust match statements, as
+ well:
+
+	switch (value) { /* aligning stuff to make it easier to read is fine */
+		case possibility: variable = foo;  break;
+		default:          variable = NULL; break;
+	}
+
+ 1. Switch cases in C and match arms in Rust should start another level of
+ indentation:
+
+	switch (value) {
+		case possibility:
+			statement;
+			break;
+		default:
+			statement;
+			break;
+	}
+
+	match result {
+		Ok(n) => variable = n,
+		Err(e) => error = e,
+	}
+
+ 2. Braces in control flow where their inclusion is left optional in C:
+
+	if (condition) { statement; }
+
+ 3. Empty lines between different kinds of statements:
 
 	int t;
 
@@ -25,56 +65,57 @@ consistent with the style of the rest of the Bonsai Computer System.
 
 	return io;
 
-3. Each block of code should be indented once more than the keyword which
-initiated the block:
+ 4. Compiler options that yield the most useful warnings, such as -Wpedantic in
+ a lot of C compilers. Fix the warnings, too [0].
 
-	switch (c) {
-		case 'e': mode |= EQUAL;   break;
-		case 'g': mode |= GREATER; break;
-		case 'l': mode |= LESS;    break;
-		default:  return usage(s);
-	}
-
-4. In C, spaces should be placed in control flow statements after the keyword
-and before the opening brace:
-
-	for (i = 2; i < argc; ++i) {
-
-5. If a function, a C control flow statement, or a Rust macro has arguments that
-cause the statement to be broken into multiple lines, this should be done by
-placing the arguments on a new line inside the parentheses: 
+ 5. One more level of indentation and one argument per line when a function
+ call or statement header is too long to fit on one line:
 
 	let usage = format!(
 		"Usage: {} [-d delimiter] index command [args...]",
 		argv[0],
 	);
 
-6. If Rust function arguments or fields are on their own lines, they should
-always have a trailing comma:
+ 6. One more level of indentation than the keyword that initiated a multi-line
+ block.
+
+	if (condition) {
+		statement;
+		statement;
+	}
+
+ 7. The return value of all non-void functions, or explicitly ignore them (like
+ casting to void in C) [0]:
+
+	if ((a = malloc(sizeof char)) == NULL) {          /* handle this error */
+		(void)fprintf(stderr, "oh noes!");   /* explicitly ignore this one */
+		return EX_OSERR;       /* ...because the program is exiting anyway */
+	}
+
+ 8. The smallest possible scope for data [0].
+
+ 9. Comments noting all the symbols and macros used from a C header file, next
+ to its include macro:
+
+	#include <unistd.h> /* close(2), getopt(3), lseek(2), read(2), write(2),
+	(space-aligned)      * optarg, optind, STDIN_FILENO, STDOUT_FILENO */
+
+ 10. Spaces in control flow statements, after the keyword and before the
+ opening brace:
+
+	for (i = 2; i < argc; ++i) {
+
+
+ 11. In Rust, a trailing comma on all arguments or fields that are on their own
+ lines:
 
 	return Err(EvaluationError {
 		message: format!("{}: Invalid token", i),
 		code: EX_DATAERR,
 	})
 
-7. If text is on the same line as a brace, spaces should be placed after an
-opening curly brace and before a closing one:
-
-	use sysexits::{ EX_DATAERR, EX_IOERR, EX_UNAVAILABLE, EX_USAGE };
-
-8. If a control flow statement is short enough to be easily understood in a
-glance, it may be placed on a single line:
-
-	if !(argc < 0) { usage(program_name); }
-
-9. In C, note everything you use from a library in a comment subsequent to its
-#include statement:
-
-	#include <unistd.h> /* close(2), getopt(3), lseek(2), read(2), write(2),
-                         * optarg, optind, STDIN_FILENO, STDOUT_FILENO */
-
-10. In Rust, place extern statements after use statements that include standard
-library crates. Group alike statements:
+ 12. In Rust, place extern statements after use statements that include standard
+ library crates. Group like statements:
 
 	use std::fs::Path;
 
@@ -84,40 +125,129 @@ library crates. Group alike statements:
 	use strerror::StrError;
 	use sysexits::{ EX_OSERR, EX_USAGE };
 
-11. Do not use do while loops in C.
+ 13. If text is on the same line as a brace, spaces after an opening brace and
+ before a closing one:
 
-12. Adhere to the following rules from the paper The Power of 10: Rules for
-Developing Safety-Critical Code [0]:
-	1. Avoid complex flow constructs, such as goto and recursion.
-	2. All loops must have fixed bounds. This prevents runaway code.
-	3. Avoid heap memory allocation.
-	4. Restrict functions to the length of a single printed page.
+	use sysexits::{ EX_DATAERR, EX_IOERR, EX_UNAVAILABLE, EX_USAGE };
 
-	6. Restrict the scope of data to the smallest possible.
-	7. Check the return value of all non-void functions, or cast to void to
-	indicate the return value is useless (such as in the case of using
-	fprintf(3p)	to print to the standard error).
-	8. Use the preprocessor sparingly.
-	9. Limit pointer use to a single dereference, and do not use function
-	pointers.
-	10. Compile with all possible warnings active; all warnings should then be
-	addressed before release of the software (for C compilers, compile with
-	-Wpedantic).
+ 14. Alphabetic sorting, where applicable:
 
-13. Remember this quote from The Elements of Programming Style by Brian
-Kernighan:
-	Everyone knows that debugging is twice as hard as writing a program in the
-	first place. So if you're as clever as you can be when you write it, how
-	will you ever debug it?
+	use std::io::{ BufWriter, Read, Write, stderr, stdin, stdout }
+
+ 15. In Rust, use the to_owned() method on string types (str, OsStr, CStr, etc.)
+ and the to_string() method on other types.
+
+
+Avoid
+=====
+
+ 16. Unbounded loops [0].
+
+ 17. Function pointers [0].
+
+ 18. Heap memory allocation [0].
+
+ 19. Using too much nested logic (within reason).
+
+ 20. Too many levels of dereferences [0]:
+
+	/* do not do this */
+	for (size_t i = 0; i < sizeof a / sizeof *a; ++i) {
+		if (a[i].id == MATCH) { a[i].val = 0; }
+	}
+
+	/* do this */
+	for (struct MadeUp *s = &a[0]; *s != NULL; s = &s[1]) {
+		if (s->id == MATCH) { s->val = 0; }
+	}
+
+ 21. Using C preprocessor macros; the fewer, the better [0].
+
+ 22. The exit(3p) and std::process::exit() functions; returning from the main
+ function skips a system call.
+
+
+Do Not Use
+==========
+
+ 23. More than the length of one printed page for a function [0].
+
+ 24. Recursion, as it’s complex and can unexpectedly overflow the stack [0].
+
+ 25. Any functionality not in the POSIX C specification and language features not
+ in C99.
+
+ 26. Do-while loops, as they’re unique to C and confusing for casual programmers.
+
+ 27. Labels and goto statements; use sensible flow control [0].
+
+ 28. Pointer arithmetic, as it tends to be confusing and unnecessary; use
+ index-reference patterns like &p[1] instead of p + 1. &p[n] is the address at
+ p + sizeof p * n, not p + n, like pointer arithmetic suggests.
+
+ 29. C struct bitfields in unions, to access certain bits of bigger data types,
+ as it’s poorly defined in the C standards; use bit arithmetic.
+
+ 30. C trigraphs.
+
+ 31. Inclusions in C header files, to prevent multiple file inclusions.
+
+ 32. C preprocessor variables to prevent multiple inclusions of the same file,
+ such as:
+
+	#ifdef _FILE
+	#define _FILE
+	/* file body */
+	#endif /* ifdef _FILE */
+
+ Instead, take the time to ensure other files aren’t including any files twice.
+
+ 33. The gets(3p) function from <stdio.h>, as it’s impossible to prevent buffer
+ overflows when it's used; use fgets(3p) from <stdio.h>.
+
+ 34. The scanf(3p) function from <stdio.h> [1].
+
+ 35. Any functionality not described in the latest POSIX make(1) specification.
+
+ 36. Macros which panic on failure in Rust (such as the print!() and println!()
+ macros). Use a function and handle any errors. However, do use the eprintln!()
+ macro for error messages. Handling an error for writing an error message is
+ redundant.
+
+
+Usage Text
+==========
+
+This section is adapted from the NetBSD style guide [2].
+
+When programs are invoked incorrectly and in the synopsis of manual pages, uasge
+text should be provided to the user. The following is the format used by this
+project for this purpose:
+
+All optional arguments are to be placed in square brackets (U+005B, U+005D).
+Mutually exclusive arguments can be separated by a vertical line (U+007C).
+Groups of arguments should be specified in alphabetical order in most cases. The
+order of arguments and an example of these rules follows:
+
+ 0. Options with no option arguments.
+ 1. Options with option arguments. Arguments should be specified inside the same
+ square brackets as the options.
+ 3. Non-option arguments.
+
+	"usage: f [-aDde] [-b b_arg] [-m m_arg] req1 req2 [opt1 [opt2]]\n"
+	"usage: f [-a | -b] [-c [-de] [-n number]]\n"
 
 
 References
 ==========
 
 [0] <https://web.eecs.umich.edu/~imarkov/10rules.pdf>
+[1] <http://sekrit.de/webdocs/c/beginners-guide-away-from-scanf.html>
+[2] <http://cvsweb.netbsd.org/bsdweb.cgi/~checkout~/src/share/misc/style>
 
 --
 Copyright © 2024 Emma Tebibyte <emma@tebibyte.media>
+Copyright © 2024 DTB <trinity@trinity.moe>
 Copyright © Wikipedia contributors
 
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