mirror of
https://github.com/neovim/neovim.git
synced 2024-12-29 14:41:06 -07:00
946 lines
31 KiB
Plaintext
946 lines
31 KiB
Plaintext
*dev_style.txt* Nvim
|
|
|
|
|
|
NVIM REFERENCE MANUAL
|
|
|
|
|
|
Nvim style guide *dev-style*
|
|
|
|
This is style guide for developers working on Nvim's source code.
|
|
|
|
License: CC-By 3.0 https://creativecommons.org/licenses/by/3.0/
|
|
|
|
Type |gO| to see the table of contents.
|
|
|
|
==============================================================================
|
|
Background
|
|
|
|
One way in which we keep the code base manageable is by enforcing consistency.
|
|
It is very important that any programmer be able to look at another's code and
|
|
quickly understand it.
|
|
|
|
Maintaining a uniform style and following conventions means that we can more
|
|
easily use "pattern-matching" to infer what various symbols are and what
|
|
invariants are true about them. Creating common, required idioms and patterns
|
|
makes code much easier to understand.
|
|
|
|
In some cases there might be good arguments for changing certain style rules,
|
|
but we nonetheless keep things as they are in order to preserve consistency.
|
|
|
|
|
|
==============================================================================
|
|
Header Files *dev-style-header*
|
|
|
|
|
|
Header guard ~
|
|
|
|
All header files should start with `#pragma once` to prevent multiple inclusion.
|
|
|
|
In foo/bar.h:
|
|
>c
|
|
#pragma once
|
|
<
|
|
|
|
Headers system ~
|
|
|
|
Nvim uses two types of headers. There are "normal" headers and "defs" headers.
|
|
Typically, each normal header will have a corresponding defs header, e.g.
|
|
`fileio.h` and `fileio_defs.h`. This distinction is done to minimize
|
|
recompilation on change. The goal is to achieve the following:
|
|
|
|
- All headers (defs and normal) must include only defs headers, system
|
|
headers, and generated declarations. In other words, headers must not
|
|
include normal headers.
|
|
|
|
- Source (.c) files may include all headers, but should only include normal
|
|
headers if they need symbols and not types.
|
|
|
|
Use the following guideline to determine what to put where:
|
|
|
|
Symbols:
|
|
- regular function declarations
|
|
- `extern` variables (including the `EXTERN` macro)
|
|
|
|
Non-symbols:
|
|
- macros, i.e. `#define`.
|
|
- static inline functions, but only if its function declaration has a
|
|
`REAL_FATTR_ALWAYS_INLINE` attribute.
|
|
- typedefs
|
|
- structs
|
|
- enums
|
|
|
|
|
|
- All symbols must be moved to normal headers.
|
|
|
|
- Non-symbols used by multiple headers should be moved to defs headers. This
|
|
is to ensure headers only include defs headers. Conversely, non-symbols used
|
|
by only a single header should be moved to that header.
|
|
|
|
- EXCEPTION: if the macro calls a function, then it must be moved to a normal
|
|
header.
|
|
|
|
==============================================================================
|
|
Scoping *dev-style-scope*
|
|
|
|
Local Variables ~
|
|
|
|
Place a function's variables in the narrowest scope possible, and initialize
|
|
variables in the declaration.
|
|
|
|
C99 allows you to declare variables anywhere in a function. Declare them in as
|
|
local a scope as possible, and as close to the first use as possible. This
|
|
makes it easier for the reader to find the declaration and see what type the
|
|
variable is and what it was initialized to. In particular, initialization
|
|
should be used instead of declaration and assignment, e.g. >c
|
|
|
|
int i;
|
|
i = f(); // BAD: initialization separate from declaration.
|
|
|
|
int j = g(); // GOOD: declaration has initialization.
|
|
|
|
|
|
Initialization ~
|
|
|
|
Multiple declarations can be defined in one line if they aren't initialized,
|
|
but each initialization should be done on a separate line.
|
|
|
|
>c
|
|
int i;
|
|
int j; // GOOD
|
|
|
|
int i, j; // GOOD: multiple declarations, no initialization.
|
|
|
|
int i = 0;
|
|
int j = 0; // GOOD: one initialization per line.
|
|
|
|
int i = 0, j; // BAD: multiple declarations with initialization.
|
|
|
|
int i = 0, j = 0; // BAD: multiple declarations with initialization.
|
|
|
|
==============================================================================
|
|
Nvim-Specific Magic
|
|
|
|
clint ~
|
|
|
|
Use `clint.py` to detect style errors.
|
|
|
|
`src/clint.py` is a Python script that reads a source file and identifies
|
|
style errors. It is not perfect, and has both false positives and false
|
|
negatives, but it is still a valuable tool. False positives can be ignored by
|
|
putting `// NOLINT` at the end of the line.
|
|
|
|
uncrustify ~
|
|
|
|
src/uncrustify.cfg is the authority for expected code formatting, for cases
|
|
not covered by clint.py. We remove checks in clint.py if they are covered by
|
|
uncrustify rules.
|
|
|
|
==============================================================================
|
|
Other C Features *dev-style-features*
|
|
|
|
|
|
Variable-Length Arrays and alloca() ~
|
|
|
|
We do not allow variable-length arrays or `alloca()`.
|
|
|
|
Variable-length arrays can cause hard to detect stack overflows.
|
|
|
|
|
|
Postincrement and Postdecrement ~
|
|
|
|
Use postfix form (`i++`) in statements. >c
|
|
|
|
for (int i = 0; i < 3; i++) { }
|
|
int j = ++i; // OK: ++i is used as an expression.
|
|
|
|
for (int i = 0; i < 3; ++i) { }
|
|
++i; // BAD: ++i is used as a statement.
|
|
|
|
|
|
Use of const ~
|
|
|
|
Use `const` pointers whenever possible. Avoid `const` on non-pointer parameter definitions.
|
|
|
|
Where to put the const ~
|
|
|
|
Some people favor the form `int const *foo` to `const int *foo` . They
|
|
argue that this is more readable because it's more consistent: it keeps
|
|
the rule that `const` always follows the object it's describing. However,
|
|
this consistency argument doesn't apply in codebases with few
|
|
deeply-nested pointer expressions since most `const` expressions have only
|
|
one `const`, and it applies to the underlying value. In such cases, there's
|
|
no consistency to maintain. Putting the `const` first is arguably more
|
|
readable, since it follows English in putting the "adjective" (`const`)
|
|
before the "noun" (`int`).
|
|
|
|
That said, while we encourage putting `const` first, we do not require it.
|
|
But be consistent with the code around you! >c
|
|
|
|
void foo(const char *p, int i);
|
|
}
|
|
|
|
int foo(const int a, const bool b) {
|
|
}
|
|
|
|
int foo(int *const p) {
|
|
}
|
|
|
|
|
|
Integer Types ~
|
|
|
|
Of the built-in integer types only use `char`, `int`, `uint8_t`, `int8_t`,
|
|
`uint16_t`, `int16_t`, `uint32_t`, `int32_t`, `uint64_t`, `int64_t`,
|
|
`uintmax_t`, `intmax_t`, `size_t`, `ssize_t`, `uintptr_t`, `intptr_t`, and
|
|
`ptrdiff_t`.
|
|
|
|
Use `int` for error codes and local, trivial variables only.
|
|
|
|
Use care when converting integer types. Integer conversions and promotions can
|
|
cause non-intuitive behavior. Note that the signedness of `char` is
|
|
implementation defined.
|
|
|
|
Public facing types must have fixed width (`uint8_t`, etc.)
|
|
|
|
There are no convenient `printf` format placeholders for fixed width types.
|
|
Cast to `uintmax_t` or `intmax_t` if you have to format fixed width integers.
|
|
|
|
Type unsigned signed
|
|
`char` `%hhu` `%hhd`
|
|
`int` n/a `%d`
|
|
`(u)intmax_t` `%ju` `%jd`
|
|
`(s)size_t` `%zu` `%zd`
|
|
`ptrdiff_t` `%tu` `%td`
|
|
|
|
|
|
Booleans ~
|
|
|
|
Use `bool` to represent boolean values. >c
|
|
|
|
int loaded = 1; // BAD: loaded should have type bool.
|
|
|
|
|
|
Conditions ~
|
|
|
|
Don't use "yoda-conditions". Use at most one assignment per condition. >c
|
|
|
|
if (1 == x) {
|
|
|
|
if (x == 1) { //use this order
|
|
|
|
if ((x = f()) && (y = g())) {
|
|
|
|
|
|
Function declarations ~
|
|
|
|
Every function must not have a separate declaration.
|
|
|
|
Function declarations are created by the gen_declarations.lua script. >c
|
|
|
|
static void f(void);
|
|
|
|
static void f(void)
|
|
{
|
|
...
|
|
}
|
|
|
|
|
|
General translation unit layout ~
|
|
|
|
The definitions of public functions precede the definitions of static
|
|
functions. >c
|
|
|
|
<HEADER>
|
|
|
|
<PUBLIC FUNCTION DEFINITIONS>
|
|
|
|
<STATIC FUNCTION DEFINITIONS>
|
|
|
|
|
|
Integration with declarations generator ~
|
|
|
|
Every C file must contain #include of the generated header file, guarded by
|
|
#ifdef INCLUDE_GENERATED_DECLARATIONS.
|
|
|
|
Include must go after other #includes and typedefs in .c files and after
|
|
everything else in header files. It is allowed to omit #include in a .c file
|
|
if .c file does not contain any static functions.
|
|
|
|
Included file name consists of the .c file name without extension, preceded by
|
|
the directory name relative to src/nvim. Name of the file containing static
|
|
functions declarations ends with `.c.generated.h`, `*.h.generated.h` files
|
|
contain only non-static function declarations. >c
|
|
|
|
// src/nvim/foo.c file
|
|
#include <stddef.h>
|
|
|
|
typedef int FooType;
|
|
|
|
#ifdef INCLUDE_GENERATED_DECLARATIONS
|
|
# include "foo.c.generated.h"
|
|
#endif
|
|
|
|
…
|
|
|
|
|
|
// src/nvim/foo.h file
|
|
#pragma once
|
|
|
|
…
|
|
|
|
#ifdef INCLUDE_GENERATED_DECLARATIONS
|
|
# include "foo.h.generated.h"
|
|
#endif
|
|
|
|
|
|
64-bit Portability ~
|
|
|
|
Code should be 64-bit and 32-bit friendly. Bear in mind problems of printing,
|
|
comparisons, and structure alignment.
|
|
|
|
- Remember that `sizeof(void *)` != `sizeof(int)`. Use `intptr_t` if you want
|
|
a pointer-sized integer.
|
|
|
|
- You may need to be careful with structure alignments, particularly for
|
|
structures being stored on disk. Any class/structure with a
|
|
`int64_t`/`uint64_t` member will by default end up being 8-byte aligned on a
|
|
64-bit system. If you have such structures being shared on disk between
|
|
32-bit and 64-bit code, you will need to ensure that they are packed the
|
|
same on both architectures. Most compilers offer a way to alter structure
|
|
alignment. For gcc, you can use `__attribute__((packed))`. MSVC offers
|
|
`#pragma pack()` and `__declspec(align())`.
|
|
|
|
- Use the `LL` or `ULL` suffixes as needed to create 64-bit constants. For
|
|
example: >c
|
|
|
|
int64_t my_value = 0x123456789LL;
|
|
uint64_t my_mask = 3ULL << 48;
|
|
|
|
|
|
sizeof ~
|
|
|
|
Prefer `sizeof(varname)` to `sizeof(type)`.
|
|
|
|
Use `sizeof(varname)` when you take the size of a particular variable.
|
|
`sizeof(varname)` will update appropriately if someone changes the variable
|
|
type either now or later. You may use `sizeof(type)` for code unrelated to any
|
|
particular variable, such as code that manages an external or internal data
|
|
format where a variable of an appropriate C type is not convenient. >c
|
|
|
|
Struct data;
|
|
memset(&data, 0, sizeof(data));
|
|
|
|
memset(&data, 0, sizeof(Struct));
|
|
|
|
if (raw_size < sizeof(int)) {
|
|
fprintf(stderr, "compressed record not big enough for count: %ju", raw_size);
|
|
return false;
|
|
}
|
|
|
|
|
|
==============================================================================
|
|
Naming *dev-style-naming*
|
|
|
|
The most important consistency rules are those that govern naming. The style
|
|
of a name immediately informs us what sort of thing the named entity is: a
|
|
type, a variable, a function, a constant, a macro, etc., without requiring us
|
|
to search for the declaration of that entity. The pattern-matching engine in
|
|
our brains relies a great deal on these naming rules.
|
|
|
|
Naming rules are pretty arbitrary, but we feel that consistency is more
|
|
important than individual preferences in this area, so regardless of whether
|
|
you find them sensible or not, the rules are the rules.
|
|
|
|
|
|
General Naming Rules ~
|
|
|
|
Function names, variable names, and filenames should be descriptive; eschew
|
|
abbreviation.
|
|
|
|
Give as descriptive a name as possible, within reason. Do not worry about
|
|
saving horizontal space as it is far more important to make your code
|
|
immediately understandable by a new reader. Do not use abbreviations that are
|
|
ambiguous or unfamiliar to readers outside your project, and do not abbreviate
|
|
by deleting letters within a word. >c
|
|
|
|
int price_count_reader; // No abbreviation.
|
|
int num_errors; // "num" is a widespread convention.
|
|
int num_dns_connections; // Most people know what "DNS" stands for.
|
|
|
|
int n; // Meaningless.
|
|
int nerr; // Ambiguous abbreviation.
|
|
int n_comp_conns; // Ambiguous abbreviation.
|
|
int wgc_connections; // Only your group knows what this stands for.
|
|
int pc_reader; // Lots of things can be abbreviated "pc".
|
|
int cstmr_id; // Deletes internal letters.
|
|
|
|
|
|
File Names ~
|
|
|
|
Filenames should be all lowercase and can include underscores (`_`).
|
|
|
|
Use underscores to separate words. Examples of acceptable file names: >
|
|
|
|
my_useful_file.c
|
|
getline_fix.c // OK: getline refers to the glibc function.
|
|
|
|
C files should end in `.c` and header files should end in `.h`.
|
|
|
|
Do not use filenames that already exist in `/usr/include`, such as `db.h`.
|
|
|
|
In general, make your filenames very specific. For example, use
|
|
`http_server_logs.h` rather than `logs.h`.
|
|
|
|
|
|
Type Names ~
|
|
|
|
Typedef-ed structs and enums start with a capital letter and have a capital
|
|
letter for each new word, with no underscores: `MyExcitingStruct`.
|
|
|
|
Non-Typedef-ed structs and enums are all lowercase with underscores between
|
|
words: `struct my_exciting_struct` . >c
|
|
|
|
struct my_struct {
|
|
...
|
|
};
|
|
typedef struct my_struct MyAwesomeStruct;
|
|
|
|
|
|
Variable Names ~
|
|
|
|
Variable names are all lowercase, with underscores between words. For
|
|
instance: `my_exciting_local_variable`.
|
|
|
|
Common Variable names ~
|
|
|
|
For example: >c
|
|
|
|
string table_name; // OK: uses underscore.
|
|
string tablename; // OK: all lowercase.
|
|
|
|
string tableName; // BAD: mixed case.
|
|
<
|
|
|
|
Struct Variables ~
|
|
|
|
Data members in structs should be named like regular variables. >c
|
|
|
|
struct url_table_properties {
|
|
string name;
|
|
int num_entries;
|
|
}
|
|
<
|
|
|
|
Global Variables ~
|
|
|
|
Don't use global variables unless absolutely necessary. Prefix global
|
|
variables with `g_`.
|
|
|
|
|
|
Constant Names ~
|
|
|
|
Use a `k` followed by mixed case: `kDaysInAWeek`.
|
|
|
|
All compile-time constants, whether they are declared locally or globally,
|
|
follow a slightly different naming convention from other variables. Use a `k`
|
|
followed by words with uppercase first letters: >c
|
|
|
|
const int kDaysInAWeek = 7;
|
|
|
|
Function Names ~
|
|
|
|
Function names are all lowercase, with underscores between words. For
|
|
instance: `my_exceptional_function()`. All functions in the same header file
|
|
should have a common prefix.
|
|
|
|
In `os_unix.h`: >c
|
|
|
|
void unix_open(const char *path);
|
|
void unix_user_id(void);
|
|
|
|
If your function crashes upon an error, you should append `or_die` to the
|
|
function name. This only applies to functions which could be used by
|
|
production code and to errors that are reasonably likely to occur during
|
|
normal operation.
|
|
|
|
|
|
Enumerator Names ~
|
|
|
|
Enumerators should be named like constants: `kEnumName`. >c
|
|
|
|
enum url_table_errors {
|
|
kOK = 0,
|
|
kErrorOutOfMemory,
|
|
kErrorMalformedInput,
|
|
};
|
|
|
|
|
|
Macro Names ~
|
|
|
|
They're like this: `MY_MACRO_THAT_SCARES_CPP_DEVELOPERS`. >c
|
|
|
|
#define ROUND(x) ...
|
|
#define PI_ROUNDED 5.0
|
|
|
|
|
|
==============================================================================
|
|
Comments *dev-style-comments*
|
|
|
|
Comments are vital to keeping our code readable. The following rules describe
|
|
what you should comment and where. But remember: while comments are very
|
|
important, the best code is self-documenting.
|
|
|
|
When writing your comments, write for your audience: the next contributor who
|
|
will need to understand your code. Be generous — the next one may be you!
|
|
|
|
Nvim uses Doxygen comments.
|
|
|
|
|
|
Comment Style ~
|
|
|
|
Use the `//`-style syntax only. >c
|
|
|
|
// This is a comment spanning
|
|
// multiple lines
|
|
f();
|
|
|
|
|
|
File Comments ~
|
|
|
|
Start each file with a description of its contents.
|
|
|
|
Legal Notice ~
|
|
|
|
We have no such thing. These things are in LICENSE and only there.
|
|
|
|
File Contents ~
|
|
|
|
Every file should have a comment at the top describing its contents.
|
|
|
|
Generally a `.h` file will describe the variables and functions that are
|
|
declared in the file with an overview of what they are for and how they
|
|
are used. A `.c` file should contain more information about implementation
|
|
details or discussions of tricky algorithms. If you feel the
|
|
implementation details or a discussion of the algorithms would be useful
|
|
for someone reading the `.h`, feel free to put it there instead, but
|
|
mention in the `.c` that the documentation is in the `.h` file.
|
|
|
|
Do not duplicate comments in both the `.h` and the `.c`. Duplicated
|
|
comments diverge. >c
|
|
|
|
/// A brief description of this file.
|
|
///
|
|
/// A longer description of this file.
|
|
/// Be very generous here.
|
|
|
|
|
|
Struct Comments ~
|
|
|
|
Every struct definition should have accompanying comments that describes what
|
|
it is for and how it should be used. >c
|
|
|
|
/// Window info stored with a buffer.
|
|
///
|
|
/// Two types of info are kept for a buffer which are associated with a
|
|
/// specific window:
|
|
/// 1. Each window can have a different line number associated with a
|
|
/// buffer.
|
|
/// 2. The window-local options for a buffer work in a similar way.
|
|
/// The window-info is kept in a list at g_wininfo. It is kept in
|
|
/// most-recently-used order.
|
|
struct win_info {
|
|
/// Next entry or NULL for last entry.
|
|
WinInfo *wi_next;
|
|
/// Previous entry or NULL for first entry.
|
|
WinInfo *wi_prev;
|
|
/// Pointer to window that did the wi_fpos.
|
|
Win *wi_win;
|
|
...
|
|
};
|
|
|
|
If the field comments are short, you can also put them next to the field. But
|
|
be consistent within one struct, and follow the necessary doxygen style. >c
|
|
|
|
struct wininfo_S {
|
|
WinInfo *wi_next; ///< Next entry or NULL for last entry.
|
|
WinInfo *wi_prev; ///< Previous entry or NULL for first entry.
|
|
Win *wi_win; ///< Pointer to window that did the wi_fpos.
|
|
...
|
|
};
|
|
|
|
If you have already described a struct in detail in the comments at the top of
|
|
your file feel free to simply state "See comment at top of file for a complete
|
|
description", but be sure to have some sort of comment.
|
|
|
|
Document the synchronization assumptions the struct makes, if any. If an
|
|
instance of the struct can be accessed by multiple threads, take extra care to
|
|
document the rules and invariants surrounding multithreaded use.
|
|
|
|
|
|
Function Comments ~
|
|
|
|
Declaration comments describe use of the function; comments at the definition
|
|
of a function describe operation.
|
|
|
|
Function Declarations ~
|
|
|
|
Every function declaration should have comments immediately preceding it
|
|
that describe what the function does and how to use it. These comments
|
|
should be descriptive ("Opens the file") rather than imperative ("Open the
|
|
file"); the comment describes the function, it does not tell the function
|
|
what to do. In general, these comments do not describe how the function
|
|
performs its task. Instead, that should be left to comments in the
|
|
function definition.
|
|
|
|
Types of things to mention in comments at the function declaration:
|
|
|
|
- If the function allocates memory that the caller must free.
|
|
- Whether any of the arguments can be a null pointer.
|
|
- If there are any performance implications of how a function is used.
|
|
- If the function is re-entrant. What are its synchronization assumptions? >c
|
|
/// Brief description of the function.
|
|
///
|
|
/// Detailed description.
|
|
/// May span multiple paragraphs.
|
|
///
|
|
/// @param arg1 Description of arg1
|
|
/// @param arg2 Description of arg2. May span
|
|
/// multiple lines.
|
|
///
|
|
/// @return Description of the return value.
|
|
Iterator *get_iterator(void *arg1, void *arg2);
|
|
<
|
|
|
|
Function Definitions ~
|
|
|
|
If there is anything tricky about how a function does its job, the
|
|
function definition should have an explanatory comment. For example, in
|
|
the definition comment you might describe any coding tricks you use, give
|
|
an overview of the steps you go through, or explain why you chose to
|
|
implement the function in the way you did rather than using a viable
|
|
alternative. For instance, you might mention why it must acquire a lock
|
|
for the first half of the function but why it is not needed for the second
|
|
half.
|
|
|
|
Note you should not just repeat the comments given with the function
|
|
declaration, in the `.h` file or wherever. It's okay to recapitulate
|
|
briefly what the function does, but the focus of the comments should be on
|
|
how it does it. >c
|
|
|
|
// Note that we don't use Doxygen comments here.
|
|
Iterator *get_iterator(void *arg1, void *arg2)
|
|
{
|
|
...
|
|
}
|
|
|
|
|
|
Variable Comments ~
|
|
|
|
In general the actual name of the variable should be descriptive enough to
|
|
give a good idea of what the variable is used for. In certain cases, more
|
|
comments are required.
|
|
|
|
Global Variables ~
|
|
|
|
All global variables should have a comment describing what they are and
|
|
what they are used for. For example: >c
|
|
|
|
/// The total number of tests cases that we run
|
|
/// through in this regression test.
|
|
const int kNumTestCases = 6;
|
|
|
|
|
|
Implementation Comments ~
|
|
|
|
In your implementation you should have comments in tricky, non-obvious,
|
|
interesting, or important parts of your code.
|
|
|
|
Line Comments ~
|
|
|
|
Also, lines that are non-obvious should get a comment at the end of the
|
|
line. These end-of-line comments should be separated from the code by 2
|
|
spaces. Example: >c
|
|
|
|
// If we have enough memory, mmap the data portion too.
|
|
mmap_budget = max<int64>(0, mmap_budget - index_->length());
|
|
if (mmap_budget >= data_size_ && !MmapData(mmap_chunk_bytes, mlock)) {
|
|
return; // Error already logged.
|
|
}
|
|
<
|
|
Note that there are both comments that describe what the code is doing,
|
|
and comments that mention that an error has already been logged when the
|
|
function returns.
|
|
|
|
If you have several comments on subsequent lines, it can often be more
|
|
readable to line them up: >c
|
|
|
|
do_something(); // Comment here so the comments line up.
|
|
do_something_else_that_is_longer(); // Comment here so there are two spaces between
|
|
// the code and the comment.
|
|
{ // One space before comment when opening a new scope is allowed,
|
|
// thus the comment lines up with the following comments and code.
|
|
do_something_else(); // Two spaces before line comments normally.
|
|
}
|
|
<
|
|
|
|
NULL, true/false, 1, 2, 3... ~
|
|
|
|
When you pass in a null pointer, boolean, or literal integer values to
|
|
functions, you should consider adding a comment about what they are, or
|
|
make your code self-documenting by using constants. For example, compare:
|
|
>c
|
|
|
|
bool success = calculate_something(interesting_value,
|
|
10,
|
|
false,
|
|
NULL); // What are these arguments??
|
|
<
|
|
|
|
versus: >c
|
|
|
|
bool success = calculate_something(interesting_value,
|
|
10, // Default base value.
|
|
false, // Not the first time we're calling this.
|
|
NULL); // No callback.
|
|
<
|
|
|
|
Or alternatively, constants or self-describing variables: >c
|
|
|
|
const int kDefaultBaseValue = 10;
|
|
const bool kFirstTimeCalling = false;
|
|
Callback *null_callback = NULL;
|
|
bool success = calculate_something(interesting_value,
|
|
kDefaultBaseValue,
|
|
kFirstTimeCalling,
|
|
null_callback);
|
|
<
|
|
|
|
Don'ts ~
|
|
|
|
Note that you should never describe the code itself. Assume that the
|
|
person reading the code knows C better than you do, even though he or she
|
|
does not know what you are trying to do: >c
|
|
|
|
// Now go through the b array and make sure that if i occurs,
|
|
// the next element is i+1.
|
|
... // Geez. What a useless comment.
|
|
|
|
|
|
Punctuation, Spelling and Grammar ~
|
|
|
|
Pay attention to punctuation, spelling, and grammar; it is easier to read
|
|
well-written comments than badly written ones.
|
|
|
|
Comments should be as readable as narrative text, with proper capitalization
|
|
and punctuation. In many cases, complete sentences are more readable than
|
|
sentence fragments. Shorter comments, such as comments at the end of a line of
|
|
code, can sometimes be less formal, but you should be consistent with your
|
|
style.
|
|
|
|
Although it can be frustrating to have a code reviewer point out that you are
|
|
using a comma when you should be using a semicolon, it is very important that
|
|
source code maintain a high level of clarity and readability. Proper
|
|
punctuation, spelling, and grammar help with that goal.
|
|
|
|
|
|
TODO Comments ~
|
|
|
|
Use `TODO` comments for code that is temporary, a short-term solution, or
|
|
good-enough but not perfect.
|
|
|
|
`TODO`s should include the string `TODO` in all caps, followed by the name,
|
|
email address, or other identifier of the person who can best provide context
|
|
about the problem referenced by the `TODO`. The main purpose is to have a
|
|
consistent `TODO` format that can be searched to find the person who can
|
|
provide more details upon request. A `TODO` is not a commitment that the
|
|
person referenced will fix the problem. Thus when you create a `TODO`, it is
|
|
almost always your name that is given. >c
|
|
|
|
// TODO(kl@gmail.com): Use a "*" here for concatenation operator.
|
|
// TODO(Zeke): change this to use relations.
|
|
|
|
If your `TODO` is of the form "At a future date do something" make sure that
|
|
you either include a very specific date ("Fix by November 2005") or a very
|
|
specific event ("Remove this code when all clients can handle XML
|
|
responses.").
|
|
|
|
|
|
Deprecation Comments ~
|
|
|
|
Mark deprecated interface points with `@deprecated` docstring token.
|
|
|
|
You can mark an interface as deprecated by writing a comment containing the
|
|
word `@deprecated` in all caps. The comment goes either before the declaration
|
|
of the interface or on the same line as the declaration.
|
|
|
|
After `@deprecated`, write your name, email, or other identifier in
|
|
parentheses.
|
|
|
|
A deprecation comment must include simple, clear directions for people to fix
|
|
their callsites. In C, you can implement a deprecated function as an inline
|
|
function that calls the new interface point.
|
|
|
|
Marking an interface point `DEPRECATED` will not magically cause any callsites
|
|
to change. If you want people to actually stop using the deprecated facility,
|
|
you will have to fix the callsites yourself or recruit a crew to help you.
|
|
|
|
New code should not contain calls to deprecated interface points. Use the new
|
|
interface point instead. If you cannot understand the directions, find the
|
|
person who created the deprecation and ask them for help using the new
|
|
interface point.
|
|
|
|
|
|
==============================================================================
|
|
Formatting *dev-style-format*
|
|
|
|
Coding style and formatting are pretty arbitrary, but a project is much easier
|
|
to follow if everyone uses the same style. Individuals may not agree with
|
|
every aspect of the formatting rules, and some of the rules may take some
|
|
getting used to, but it is important that all project contributors follow the
|
|
style rules so that they can all read and understand everyone's code easily.
|
|
|
|
|
|
Non-ASCII Characters ~
|
|
|
|
Non-ASCII characters should be rare, and must use UTF-8 formatting.
|
|
|
|
You shouldn't hard-code user-facing text in source (OR SHOULD YOU?), even
|
|
English, so use of non-ASCII characters should be rare. However, in certain
|
|
cases it is appropriate to include such words in your code. For example, if
|
|
your code parses data files from foreign sources, it may be appropriate to
|
|
hard-code the non-ASCII string(s) used in those data files as delimiters. More
|
|
commonly, unittest code (which does not need to be localized) might contain
|
|
non-ASCII strings. In such cases, you should use UTF-8, since that is an
|
|
encoding understood by most tools able to handle more than just ASCII.
|
|
|
|
Hex encoding is also OK, and encouraged where it enhances readability — for
|
|
example, `"\uFEFF"`, is the Unicode zero-width no-break space character, which
|
|
would be invisible if included in the source as straight UTF-8.
|
|
|
|
|
|
Braced Initializer Lists ~
|
|
|
|
Format a braced list exactly like you would format a function call in its
|
|
place but with one space after the `{` and one space before the `}`
|
|
|
|
If the braced list follows a name (e.g. a type or variable name), format as if
|
|
the `{}` were the parentheses of a function call with that name. If there is
|
|
no name, assume a zero-length name. >c
|
|
|
|
struct my_struct m = { // Here, you could also break before {.
|
|
superlongvariablename1,
|
|
superlongvariablename2,
|
|
{ short, interior, list },
|
|
{ interiorwrappinglist,
|
|
interiorwrappinglist2 } };
|
|
|
|
|
|
Loops and Switch Statements ~
|
|
|
|
Annotate non-trivial fall-through between cases.
|
|
|
|
If not conditional on an enumerated value, switch statements should always
|
|
have a `default` case (in the case of an enumerated value, the compiler will
|
|
warn you if any values are not handled). If the default case should never
|
|
execute, simply use `abort()`: >c
|
|
|
|
switch (var) {
|
|
case 0:
|
|
...
|
|
break;
|
|
case 1:
|
|
...
|
|
break;
|
|
default:
|
|
abort();
|
|
}
|
|
|
|
Switch statements that are conditional on an enumerated value should not have
|
|
a `default` case if it is exhaustive. Explicit case labels are preferred over
|
|
`default`, even if it leads to multiple case labels for the same code. For
|
|
example, instead of: >c
|
|
|
|
case A:
|
|
...
|
|
case B:
|
|
...
|
|
case C:
|
|
...
|
|
default:
|
|
...
|
|
|
|
You should use: >c
|
|
|
|
case A:
|
|
...
|
|
case B:
|
|
...
|
|
case C:
|
|
...
|
|
case D:
|
|
case E:
|
|
case F:
|
|
...
|
|
|
|
Certain compilers do not recognize an exhaustive enum switch statement as
|
|
exhaustive, which causes compiler warnings when there is a return statement in
|
|
every case of a switch statement, but no catch-all return statement. To fix
|
|
these spurious errors, you are advised to use `UNREACHABLE` after the switch
|
|
statement to explicitly tell the compiler that the switch statement always
|
|
returns and any code after it is unreachable. For example: >c
|
|
|
|
enum { A, B, C } var;
|
|
...
|
|
switch (var) {
|
|
case A:
|
|
return 1;
|
|
case B:
|
|
return 2;
|
|
case C:
|
|
return 3;
|
|
}
|
|
UNREACHABLE;
|
|
|
|
Return Values ~
|
|
|
|
Do not needlessly surround the `return` expression with parentheses.
|
|
|
|
Use parentheses in `return expr`; only where you would use them in `x =
|
|
expr;`. >c
|
|
|
|
return result;
|
|
return (some_long_condition && another_condition);
|
|
|
|
return (value); // You wouldn't write var = (value);
|
|
return(result); // return is not a function!
|
|
|
|
|
|
Horizontal Whitespace ~
|
|
|
|
Use of horizontal whitespace depends on location.
|
|
|
|
Variables ~
|
|
>c
|
|
int long_variable = 0; // Don't align assignments.
|
|
int i = 1;
|
|
|
|
struct my_struct { // Exception: struct arrays.
|
|
const char *boy;
|
|
const char *girl;
|
|
int pos;
|
|
} my_variable[] = {
|
|
{ "Mia", "Michael", 8 },
|
|
{ "Elizabeth", "Aiden", 10 },
|
|
{ "Emma", "Mason", 2 },
|
|
};
|
|
<
|
|
|
|
==============================================================================
|
|
Parting Words
|
|
|
|
The style guide is intended to make the code more readable. If you think you
|
|
must violate its rules for the sake of clarity, do it! But please add a note
|
|
to your pull request explaining your reasoning.
|
|
|
|
|
|
vim:tw=78:ts=8:et:ft=help:norl:
|