Ruby  3.4.0dev (2024-11-22 revision 0989400a925cd201defdca9eb28eb87200b30785)
Macros
stdalign.h File Reference

(0989400a925cd201defdca9eb28eb87200b30785)

Defines RBIMPL_ALIGNAS / RBIMPL_ALIGNOF. More...

#include "ruby/internal/config.h"
#include "ruby/internal/compiler_is.h"
#include "ruby/internal/has/attribute.h"
#include "ruby/internal/has/declspec_attribute.h"
#include "ruby/internal/has/feature.h"
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Macros

#define RBIMPL_ALIGNAS   alignas
 Wraps (or simulates) alignas. More...
 
#define RBIMPL_ALIGNOF   alignof
 Wraps (or simulates) alignof. More...
 

Detailed Description

Defines RBIMPL_ALIGNAS / RBIMPL_ALIGNOF.

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

Macro Definition Documentation

◆ RBIMPL_ALIGNAS

#define RBIMPL_ALIGNAS   alignas

Wraps (or simulates) alignas.

This is C++11's alignas and is different from C11 _Alignas. For instance,

typedef struct alignas(128) foo { int foo } foo;

is a valid C++ while

typedef struct _Alignas(128) foo { int foo } foo;

is an invalid C because:

  • You cannot struct _Alignas.
  • A typedef cannot have alignments.

Definition at line 54 of file stdalign.h.

◆ RBIMPL_ALIGNOF

#define RBIMPL_ALIGNOF   alignof

Wraps (or simulates) alignof.

We want C11's _Alignof. However in spite of its clear language, compilers (including GCC and clang) tend to have buggy implementations. We have to avoid such things to resort to our own version.

See also
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69560
https://bugs.llvm.org/show_bug.cgi?id=26547

Definition at line 87 of file stdalign.h.