grpc/doc/c-style-guide.md

GRPC C STYLE GUIDE

Background

Here we document style rules for C usage in the gRPC Core library.

General

• Layout rules are defined by clang-format, and all code should be passed through clang-format. A (docker-based) script to do so is included in tools/distrib/clang_format_code.sh.

Header Files

• Public header files (those in the include/grpc tree) should compile as pedantic C89.

• Public header files should be includable from C++ programs. That is, they should include the following:

  #ifdef __cplusplus
  extern "C" {
  # endif
  
  /* ... body of file ... */
  
  #ifdef __cplusplus
  }
  # endif
  

• Header files should be self-contained and end in .h.

• All header files should have a #define guard to prevent multiple inclusion. To guarantee uniqueness they should be based on the file's path.

  For public headers: include/grpc/grpc.h → GRPC_GRPC_H

  For private headers: src/core/channel/channel_stack.h → GRPC_INTERNAL_CORE_CHANNEL_CHANNEL_STACK_H

Variable Initialization

When declaring a (non-static) pointer variable, always initialize it to NULL. Even in the case of static pointer variables, it's recommended to explicitly initialize them to NULL.

C99 Features

• Variable sized arrays are not allowed.
• Do not use the 'inline' keyword.
• Flexible array members are allowed (https://en.wikipedia.org/wiki/Flexible_array_member).

Comments

Within public header files, only /* */ comments are allowed.

Within implementation files and private headers, either single line // or multi line /* */ comments are allowed. Only one comment style per file is allowed however (i.e. if single line comments are used anywhere within a file, ALL comments within that file must be single line comments).

Symbol Names

• Non-static functions must be prefixed by grpc_
• Static functions must not be prefixed by grpc_
• Enumeration values and #define names must be uppercase. All other values must be lowercase.
• Multiple word identifiers use underscore as a delimiter, never camel case. E.g. variable_name.

Functions

• The use of atexit() is in forbidden in libgrpc.