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/lib/channel/channel_stack.h → GRPC_CORE_LIB_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_
• Typenames of structs , unions, and enums must be prefixed by grpc_ if they are declared in a header file. They must not be prefixed by grpc_ if they are declared in a source file.
• Enumeration values and #define names must be uppercase. All other values must be lowercase.
• Enumeration values or #define names defined in a header file must be prefixed with GRPC_ (except for #define macros that are being used to substitute functions; those should follow the general rules for functions). Enumeration values or #defines defined in source files must not be prefixed with GRPC_.
• 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.