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Overview

Godefs is a bootstrapping tool for porting the Go runtime to new systems. It translates C type declarations into C or Go type declarations with the same memory layout.

Usage: godefs [-g package] [-c cc] [-f cc-arg]... [defs.c ...]

Godefs takes as input a host-compilable C file that includes standard system headers. From that input file, it generates a standalone (no #includes) C or Go file containing equivalent definitions.

The input to godefs is a C input file that can be compiled by the host system's standard C compiler (typically gcc). This file is expected to define new types and enumerated constants whose names begin with $ (a legal identifier character in gcc). Godefs compile the given input file with the host compiler and then parses the debug info embedded in the assembly output. This is far easier than reading system headers on most machines.

The output from godefs is either C output intended for the Plan 9 C compiler tool chain (6c, 8c, or 5c) or Go output.

The options are:

-g package
	generate Go output using the given package name.
	In the Go output, struct fields have leading xx_ prefixes
	removed and the first character capitalized (exported).

-c cc
	set the name of the host system's C compiler (default "gcc")

-f cc-arg
	add cc-arg to the command line when invoking the system C compiler
	(for example, -f -m64 to invoke gcc -m64).
	Repeating this option adds multiple flags to the command line.

For example, if this is x.c:

#include <sys/stat.h>

typedef struct timespec $Timespec;
enum {
	$S_IFMT = S_IFMT,
	$S_IFIFO = S_IFIFO,
	$S_IFCHR = S_IFCHR,
};

then "godefs x.c" generates:

// godefs x.c
// MACHINE GENERATED - DO NOT EDIT.

// Constants
enum {
	S_IFMT = 0xf000,
	S_IFIFO = 0x1000,
	S_IFCHR = 0x2000,
};

// Types
#pragma pack on

typedef struct Timespec Timespec;
struct Timespec {
	int64 tv_sec;
	int64 tv_nsec;
};
#pragma pack off

and "godefs -g MyPackage x.c" generates:

// godefs -g MyPackage x.c
// MACHINE GENERATED - DO NOT EDIT.

package MyPackage

// Constants
const (
	S_IFMT = 0xf000;
	S_IFIFO = 0x1000;
	S_IFCHR = 0x2000;
)

// Types

type Timespec struct {
	Sec int64;
	Nsec int64;
}