| *dev_style.txt* Nvim |
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| NVIM REFERENCE MANUAL |
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| Nvim style guide *dev-style* |
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| Style guidelines for developers working Nvim's source code. |
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| License: CC-By 3.0 https://creativecommons.org/licenses/by/3.0/ |
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| Type |gO| to see the table of contents. |
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| ============================================================================== |
| Background |
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| 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. |
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| 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. |
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| 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. |
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| ============================================================================== |
| Header Files *dev-style-header* |
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| Header guard ~ |
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| All header files should start with `#pragma once` to prevent multiple inclusion. |
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| In foo/bar.h: |
| >c |
| #pragma once |
| < |
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| Headers system ~ |
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| 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 reason for this is because adding a function or |
| modifying a function's signature happens more frequently than changing a type |
| The goal is to achieve the following: |
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| - All headers (defs and normal) must include only defs headers, system |
| headers, and generated declarations. In other words, headers must not |
| include normal headers. |
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| - Source (.c) files may include all headers, but should only include normal |
| headers if they need symbols and not types. |
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| Use the following guideline to determine what to put where: |
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| Symbols: |
| - regular function declarations |
| - `extern` variables (including the `EXTERN` macro) |
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| Non-symbols: |
| - macros, i.e. `#define` |
| - static inline functions with the `FUNC_ATTR_ALWAYS_INLINE` attribute |
| - typedefs |
| - structs |
| - enums |
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| - All symbols must be moved to normal headers. |
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| - 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. |
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| - EXCEPTION: if the macro calls a function, then it must be moved to a normal |
| header. |
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| ============================================================================== |
| Scoping *dev-style-scope* |
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| Local Variables ~ |
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| Place a function's variables in the narrowest scope possible, and initialize |
| variables in the declaration. |
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| 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 |
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| int i; |
| i = f(); // ❌: initialization separate from declaration. |
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| int j = g(); // ✅: declaration has initialization. |
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| Initialization ~ |
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| Multiple declarations can be defined in one line if they aren't initialized, |
| but each initialization should be done on a separate line. |
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| >c |
| int i; |
| int j; // ✅ |
| int i, j; // ✅: multiple declarations, no initialization. |
| int i = 0; |
| int j = 0; // ✅: one initialization per line. |
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| int i = 0, j; // ❌: multiple declarations with initialization. |
| int i = 0, j = 0; // ❌: multiple declarations with initialization. |
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| ============================================================================== |
| Nvim-Specific Magic |
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| clint ~ |
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| Use `clint.py` to detect style errors. |
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| `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. |
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| uncrustify ~ |
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| 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. |
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| ============================================================================== |
| Other C Features *dev-style-features* |
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| Variable-Length Arrays and alloca() ~ |
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| We do not allow variable-length arrays or `alloca()`. |
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| Variable-length arrays can cause hard to detect stack overflows. |
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| Postincrement and Postdecrement ~ |
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| Use postfix form (`i++`) in statements. >c |
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| for (int i = 0; i < 3; i++) { } |
| int j = ++i; // ✅: ++i is used as an expression. |
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| for (int i = 0; i < 3; ++i) { } |
| ++i; // ❌: ++i is used as a statement. |
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| Use of const ~ |
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| Use `const` pointers whenever possible. Avoid `const` on non-pointer parameter definitions. |
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| Where to put the const ~ |
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| 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`). |
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| That said, while we encourage putting `const` first, we do not require it. |
| But be consistent with the code around you! >c |
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| void foo(const char *p, int i); |
| } |
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| int foo(const int a, const bool b) { |
| } |
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| int foo(int *const p) { |
| } |
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| Integer Types ~ |
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| 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`. |
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| Use `int` for error codes and local, trivial variables only. |
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| Use care when converting integer types. Integer conversions and promotions can |
| cause non-intuitive behavior. Note that the signedness of `char` is |
| implementation defined. |
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| Public facing types must have fixed width (`uint8_t`, etc.) |
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| 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. |
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| Type unsigned signed |
| `char` `%hhu` `%hhd` |
| `int` n/a `%d` |
| `(u)intmax_t` `%ju` `%jd` |
| `(s)size_t` `%zu` `%zd` |
| `ptrdiff_t` `%tu` `%td` |
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| Booleans ~ |
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| Use `bool` to represent boolean values. >c |
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| int loaded = 1; // ❌: loaded should have type bool. |
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| Conditions ~ |
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| Don't use "yoda-conditions". Use at most one assignment per condition. >c |
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| if (1 == x) { |
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| if (x == 1) { //use this order |
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| if ((x = f()) && (y = g())) { |
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| Function declarations ~ |
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| Every function must not have a separate declaration. |
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| Function declarations are created by the gen_declarations.lua script. >c |
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| static void f(void); |
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| static void f(void) |
| { |
| ... |
| } |
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| General translation unit layout ~ |
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| The definitions of public functions precede the definitions of static |
| functions. >c |
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| <HEADER> |
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| <PUBLIC FUNCTION DEFINITIONS> |
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| <STATIC FUNCTION DEFINITIONS> |
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| Integration with declarations generator ~ |
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| Every C file must contain #include of the generated header file, guarded by |
| #ifdef INCLUDE_GENERATED_DECLARATIONS. |
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| 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. |
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| 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 |
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| // src/nvim/foo.c file |
| #include <stddef.h> |
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| typedef int FooType; |
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| #ifdef INCLUDE_GENERATED_DECLARATIONS |
| # include "foo.c.generated.h" |
| #endif |
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| … |
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| // src/nvim/foo.h file |
| #pragma once |
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| … |
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| #ifdef INCLUDE_GENERATED_DECLARATIONS |
| # include "foo.h.generated.h" |
| #endif |
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| 64-bit Portability ~ |
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| Code should be 64-bit and 32-bit friendly. Bear in mind problems of printing, |
| comparisons, and structure alignment. |
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| - Remember that `sizeof(void *)` != `sizeof(int)`. Use `intptr_t` if you want |
| a pointer-sized integer. |
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| - 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())`. |
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| - Use the `LL` or `ULL` suffixes as needed to create 64-bit constants. For |
| example: >c |
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| int64_t my_value = 0x123456789LL; |
| uint64_t my_mask = 3ULL << 48; |
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| sizeof ~ |
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| Prefer `sizeof(varname)` to `sizeof(type)`. |
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| 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 |
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| Struct data; |
| memset(&data, 0, sizeof(data)); |
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| memset(&data, 0, sizeof(Struct)); |
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| if (raw_size < sizeof(int)) { |
| fprintf(stderr, "compressed record not big enough for count: %ju", raw_size); |
| return false; |
| } |
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| ============================================================================== |
| Naming *dev-style-naming* |
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| 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. |
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| 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. |
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| General Naming Rules ~ |
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| Function names, variable names, and filenames should be descriptive; eschew |
| abbreviation. |
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| 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 |
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| 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. |
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| 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. |
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| File Names ~ |
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| Filenames should be all lowercase and can include underscores (`_`). |
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| Use underscores to separate words. Examples of acceptable file names: > |
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| my_useful_file.c |
| getline_fix.c // ✅: getline refers to the glibc function. |
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| C files should end in `.c` and header files should end in `.h`. |
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| Do not use filenames that already exist in `/usr/include`, such as `db.h`. |
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| In general, make your filenames very specific. For example, use |
| `http_server_logs.h` rather than `logs.h`. |
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| Type Names ~ |
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| Typedef-ed structs and enums start with a capital letter and have a capital |
| letter for each new word, with no underscores: `MyExcitingStruct`. |
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| Non-Typedef-ed structs and enums are all lowercase with underscores between |
| words: `struct my_exciting_struct` . >c |
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| struct my_struct { |
| ... |
| }; |
| typedef struct my_struct MyAwesomeStruct; |
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| Variable Names ~ |
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| Variable names are all lowercase, with underscores between words. For |
| instance: `my_exciting_local_variable`. |
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| Common Variable names ~ |
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| For example: >c |
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| string table_name; // ✅: uses underscore. |
| string tablename; // ✅: all lowercase. |
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| string tableName; // ❌: mixed case. |
| < |
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| Struct Variables ~ |
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| Data members in structs should be named like regular variables. >c |
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| struct url_table_properties { |
| string name; |
| int num_entries; |
| } |
| < |
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| Global Variables ~ |
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| Don't use global variables unless absolutely necessary. Prefix global |
| variables with `g_`. |
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| Constant Names ~ |
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| Use a `k` followed by mixed case: `kDaysInAWeek`. |
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| 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 |
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| const int kDaysInAWeek = 7; |
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| Function Names ~ |
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| 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. |
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| In `os_unix.h`: >c |
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| void unix_open(const char *path); |
| void unix_user_id(void); |
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| 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. |
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| Enumerator Names ~ |
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| Enumerators should be named like constants: `kEnumName`. >c |
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| enum url_table_errors { |
| kOK = 0, |
| kErrorOutOfMemory, |
| kErrorMalformedInput, |
| }; |
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| Macro Names ~ |
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| They're like this: `MY_MACRO_THAT_SCARES_CPP_DEVELOPERS`. >c |
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| #define ROUND(x) ... |
| #define PI_ROUNDED 5.0 |
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| ============================================================================== |
| Comments *dev-style-comments* |
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| 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. |
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| 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! |
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| Nvim uses Doxygen comments. |
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| Comment Style ~ |
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| Use the `//`-style syntax only. >c |
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| // This is a comment spanning |
| // multiple lines |
| f(); |
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| File Comments ~ |
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| Start each file with a description of its contents. |
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| Legal Notice ~ |
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| We have no such thing. These things are in LICENSE and only there. |
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| File Contents ~ |
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| Every file should have a comment at the top describing its contents. |
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| 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. |
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| Do not duplicate comments in both the `.h` and the `.c`. Duplicated |
| comments diverge. >c |
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| /// A brief description of this file. |
| /// |
| /// A longer description of this file. |
| /// Be very generous here. |
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| Struct Comments ~ |
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| Every struct definition should have accompanying comments that describes what |
| it is for and how it should be used. >c |
|
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| /// 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. |
|
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| 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. |
|
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| Function Comments ~ |
|
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| 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: |
|
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| - 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; |
|
|
|
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| Implementation Comments ~ |
|
|
| In your implementation you should have comments in tricky, non-obvious, |
| interesting, or important parts of your code. |
|
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| 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: |
|
|