Ruby: include/ruby/internal/dllexport.h File Reference

Ruby 3.4.9p82 (2026-03-11 revision 76cca827ab52ab1d346a728f068d5b8da3e2952b)

Macros
dllexport.h File Reference

Tweaking visibility of C variables/functions. More...

`#include "ruby/internal/config.h"`
`#include "ruby/internal/compiler_is.h"`

Go to the source code of this file.

## Macros
#define | RUBY_EXTERN extern
| Declaration of externally visible global variables.
#define | RBIMPL_SYMBOL_EXPORT_BEGIN()
| Shortcut macro equivalent to RUBY_SYMBOL_EXPORT_BEGIN extern "C" {.
#define | RBIMPL_SYMBOL_EXPORT_END()
| Counterpart of RBIMPL_SYMBOL_EXPORT_BEGIN.

## Detailed Description

Tweaking visibility of C variables/functions.

Author
  Ruby developers ruby-.nosp@m.core.nosp@m.@ruby.nosp@m.-lan.nosp@m.g.org

Copyright
  This file is a part of the programming language Ruby. Permission is hereby granted, to either redistribute and/or modify this file, provided that the conditions mentioned in the file COPYING are met. Consult the file for details.

Warning
  Symbols prefixed with either RBIMPL or rbimpl are implementation details. Don't take them as canon. They could rapidly appear then vanish. The name (path) of this header file is also an implementation detail. Do not expect it to persist at the place it is now. Developers are free to move it anywhere anytime at will.

Note
  To ruby-core: remember that this header can be possibly recursively included from extension libraries written in C++. Do not expect for instance __VA_ARGS__ is always available. We assume C99 for ruby itself but we don't assume languages of extension libraries. They could be written in C++98.

Definition in file dllexport.h.

## Macro Definition Documentation

## ◆ RBIMPL_SYMBOL_EXPORT_BEGIN

#define RBIMPL_SYMBOL_EXPORT_BEGIN | ( |  | ) |

Value:
/* void */

Shortcut macro equivalent to RUBY_SYMBOL_EXPORT_BEGIN extern "C" {.

@shyouhei finds it handy.

Definition at line 65 of file dllexport.h.

## ◆ RBIMPL_SYMBOL_EXPORT_END

#define RBIMPL_SYMBOL_EXPORT_END | ( |  | ) |

Value:
/* void */

Counterpart of RBIMPL_SYMBOL_EXPORT_BEGIN.

Definition at line 74 of file dllexport.h.

Referenced by rb_class_descendants(), rb_fd_select(), rb_fd_set(), rb_ivar_foreach(), rb_native_cond_destroy(), rb_num2ull(), and rb_proc_times().

## ◆ RUBY_EXTERN

#define RUBY_EXTERN extern

Declaration of externally visible global variables.

Here "externally" means they should be visible from extension libraries. Depending on operating systems (dynamic linkers, to be precise), global variables inside of a DLL may or may not be visible form outside of that DLL by default. This declaration manually tweaks that default and ensures the declared variable be truly globally visible.

extern VALUE foo; // hidden on some OS
RUBY_EXTERN VALUE foo; // ensure visible
RUBY_EXTERN
#define RUBY_EXTERN
Declaration of externally visible global variables.
Definition dllexport.h:45
VALUE
uintptr_t VALUE
Type that represents a Ruby object.
Definition value.h:40

Definition at line 45 of file dllexport.h.

Referenced by rb_define_alloc_func(), and rb_random_mark().