LLVM Coding Standard, in a nutshell

Note: 这份文件主要是为大模型 Review 我的提交时准备的，Agents 可以读取文件且非常聪明，所以不会深入细节

以及我觉得这个改一改就可以当 Agents 做其他项目时的规范，所以就放上来了。

References:

本文档是活的文档，会随着我自己的工作进展而更新内容，且不保证已有内容的正确性。

The Golden Rule

If you are extending, enhancing, or bug fixing already implemented code, use the style that is already being used so that the source is uniform and easy to follow.

You should refer to typical files in the repo when reviewing user's code. (e.g. grep -rn *.cpp)

Formatting

Run these commands after making changes/ before starting code review:

Python: darker -r HEAD^ $(git diff --name-only --diff-filter=d HEAD^)
C++: git clang-format HEAD~1

Fix/Report issues if linter failed.

Comments

C++: // for normal comments, /// for doxygen
C: Maintain C89 compatibility

Whitespace

No trailing whitespaces

Casts

No RTTI or Exceptions: dynamic_cast<> not allowed
Handrolled isa<>, cast<>, and dyn_cast<> is allowed
Prefer static_cast, reinterpret_cast, const_cast

`class` and `struct`

struct should be used when all members are declared public.
All declarations and definitions of a given class or struct must use the same keyword.

`auto`

Use auto, but be aware of unnecessary copies (e.g. range-based for loops, use auto &/*)

`#include` as Little as Possible

Less include means less code, means faster compile time/binary size/speed.
This one is very very important, you should never forget it.
Double check when reviewing/writing code.

`continue` and Early Exits

To simplify code.

No Predicate Loops, use Predicate Functions

Miscs

No Static Constructors
Don't use Braced Initializer Lists to Call a Constructor (C++11)
Always check if user's git branch name is ideal, rename when necessary.

Naming

Always check inconsistent naming when reviewing/writing code:

Type: start with an upper-case letter
Var: camel case, start with an upper-case letter
Func: imperative, verb phrases, camel case, start with a lowercase letter
Enum: If discriminator for a union, or an indicator of a subclass, add Kind Suffix, otherwise align with Type

Exception: classes that mimic STL classes can have member names in STL’s style of lowercase words separated by underscores.

Assert

Use the "assert" macro to its fullest.

Also, see llvm_unreachable

Forbidden usage

using namespace std
#include <iostream>: use llvm::MemoryBuffer

Omit braces when possible

Check UNIX newline at EOF

Preferred APIs

Please remember the #include rule

StringRef when handling std::string
Error as replacement to Exception/std::error_code
llvm::ArrayRef, TinyPtrVector, SmallVector over std::vector/list
Never use <list> to avoid heap allocation (extremely high constant factor).
Sets: SmallSet, SmallPtrSet, StringSet, DenseSet, RadixTree, SparseSet, FoldingSet..
Avoid <set>: malloc intensive, large per-element space overhead)
Map: StringMap, IndexedMap, DenseMap, ValueMap
Avoid <map>: large constant factor
Avoid std::multimap and std::unordered_map: malloc intensive
Avoid std::vector<bool>.

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