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Differential D158216

[libc++] Assume that __BYTE_ORDER__ is always present
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Authored by philnik on Aug 17 2023, 1:59 PM.

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ldionne
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Restricted Project
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rG0a97720d0197: [libc++] Assume that __BYTE_ORDER__ is always present
Summary

Both Clang and GCC always define BYTE_ORDER, so there is no need to test the byte order a million different ways.

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Event Timeline

philnik created this revision.Aug 17 2023, 1:59 PM
Herald added a project: Restricted Project. · View Herald TranscriptAug 17 2023, 1:59 PM
Herald added a subscriber: krytarowski. · View Herald Transcript
Harbormaster completed remote builds in B253305: Diff 551257.Aug 17 2023, 10:55 PM
philnik published this revision for review.Aug 18 2023, 3:35 PM
Herald added a project: Restricted Project. · View Herald TranscriptAug 18 2023, 3:35 PM
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Herald added a subscriber: libcxx-commits. · View Herald Transcript
ldionne accepted this revision.Sep 1 2023, 8:43 AM
ldionne added a subscriber: ldionne.

LGTM with suggestion applied.

libcxx/include/__config
425–429

Can we do something like

#ifndef __BYTE_ORDER__
#error "Your compiler doesn't seem to define __BYTE_ORDER__, which is required by libc++ to know the endianness of your target platform
#endif

This will catch any failure to satisfy our assumptions here.

This revision is now accepted and ready to land.Sep 1 2023, 8:43 AM
Closed by commit rG0a97720d0197: [libc++] Assume that __BYTE_ORDER__ is always present (authored by philnik). · Explain WhySep 1 2023, 9:12 AM
This revision was automatically updated to reflect the committed changes.
philnik marked an inline comment as done.
philnik added a commit: rG0a97720d0197: [libc++] Assume that __BYTE_ORDER__ is always present.

Revision Contents

PathSize
libcxx/
include/
58 lines

Diff 555410

libcxx/include/__config

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# define _LIBCPP_GLIBC_PREREQ(a, b) 0 # define _LIBCPP_GLIBC_PREREQ(a, b) 0
# endif // defined(__GLIBC_PREREQ) # endif // defined(__GLIBC_PREREQ)
# endif // defined(__linux__) # endif // defined(__linux__)
# if defined(__MVS__) # if defined(__MVS__)
# include <features.h> // for __NATIVE_ASCII_F # include <features.h> // for __NATIVE_ASCII_F
# endif # endif
# ifdef __LITTLE_ENDIAN__ # ifndef __BYTE_ORDER__
# if __LITTLE_ENDIAN__ # error \
# define _LIBCPP_LITTLE_ENDIAN "Your compiler doesn't seem to define __BYTE_ORDER__, which is required by libc++ to know the endianness of your target platform"
# endif // __LITTLE_ENDIAN__ # endif
# endif // __LITTLE_ENDIAN__
# ifdef __BIG_ENDIAN__
# if __BIG_ENDIAN__
# define _LIBCPP_BIG_ENDIAN
# endif // __BIG_ENDIAN__
# endif // __BIG_ENDIAN__
# ifdef __BYTE_ORDER__
# if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ # if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
# define _LIBCPP_LITTLE_ENDIAN # define _LIBCPP_LITTLE_ENDIAN
# elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ # elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
# define _LIBCPP_BIG_ENDIAN # define _LIBCPP_BIG_ENDIAN
# endif // __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ # endif // __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
ldionneUnsubmitted
Done
ReplyInline Actions

Can we do something like

#ifndef __BYTE_ORDER__
#error "Your compiler doesn't seem to define __BYTE_ORDER__, which is required by libc++ to know the endianness of your target platform
#endif

This will catch any failure to satisfy our assumptions here.

ldionne: Can we do something like ``` #ifndef __BYTE_ORDER__ #error "Your compiler doesn't seem to…
# endif // __BYTE_ORDER__
# ifdef __FreeBSD__
# include <osreldate.h>
# include <sys/endian.h>
# if _BYTE_ORDER == _LITTLE_ENDIAN
# define _LIBCPP_LITTLE_ENDIAN
# else // _BYTE_ORDER == _LITTLE_ENDIAN
# define _LIBCPP_BIG_ENDIAN
# endif // _BYTE_ORDER == _LITTLE_ENDIAN
# endif // __FreeBSD__
# if defined(__NetBSD__) || defined(__OpenBSD__)
# include <sys/endian.h>
# if _BYTE_ORDER == _LITTLE_ENDIAN
# define _LIBCPP_LITTLE_ENDIAN
# else // _BYTE_ORDER == _LITTLE_ENDIAN
# define _LIBCPP_BIG_ENDIAN
# endif // _BYTE_ORDER == _LITTLE_ENDIAN
# endif // defined(__NetBSD__) || defined(__OpenBSD__)
# if defined(_WIN32) # if defined(_WIN32)
# define _LIBCPP_WIN32API # define _LIBCPP_WIN32API
# define _LIBCPP_LITTLE_ENDIAN
# define _LIBCPP_SHORT_WCHAR 1 # define _LIBCPP_SHORT_WCHAR 1
// Both MinGW and native MSVC provide a "MSVC"-like environment // Both MinGW and native MSVC provide a "MSVC"-like environment
# define _LIBCPP_MSVCRT_LIKE # define _LIBCPP_MSVCRT_LIKE
// If mingw not explicitly detected, assume using MS C runtime only if // If mingw not explicitly detected, assume using MS C runtime only if
// a MS compatibility version is specified. // a MS compatibility version is specified.
# if defined(_MSC_VER) && !defined(__MINGW32__) # if defined(_MSC_VER) && !defined(__MINGW32__)
# define _LIBCPP_MSVCRT // Using Microsoft's C Runtime library # define _LIBCPP_MSVCRT // Using Microsoft's C Runtime library
# endif # endif
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# elif defined(__native_client__) # elif defined(__native_client__)
# define _LIBCPP_USING_NACL_RANDOM # define _LIBCPP_USING_NACL_RANDOM
# elif defined(_LIBCPP_WIN32API) # elif defined(_LIBCPP_WIN32API)
# define _LIBCPP_USING_WIN32_RANDOM # define _LIBCPP_USING_WIN32_RANDOM
# else # else
# define _LIBCPP_USING_DEV_RANDOM # define _LIBCPP_USING_DEV_RANDOM
# endif # endif
# if !defined(_LIBCPP_LITTLE_ENDIAN) && !defined(_LIBCPP_BIG_ENDIAN)
# include <endian.h>
# if __BYTE_ORDER == __LITTLE_ENDIAN
# define _LIBCPP_LITTLE_ENDIAN
# elif __BYTE_ORDER == __BIG_ENDIAN
# define _LIBCPP_BIG_ENDIAN
# else // __BYTE_ORDER == __BIG_ENDIAN
# error unable to determine endian
# endif
# endif // !defined(_LIBCPP_LITTLE_ENDIAN) && !defined(_LIBCPP_BIG_ENDIAN)
# if __has_attribute(__no_sanitize__) && !defined(_LIBCPP_COMPILER_GCC) # if __has_attribute(__no_sanitize__) && !defined(_LIBCPP_COMPILER_GCC)
# define _LIBCPP_NO_CFI __attribute__((__no_sanitize__("cfi"))) # define _LIBCPP_NO_CFI __attribute__((__no_sanitize__("cfi")))
# else # else
# define _LIBCPP_NO_CFI # define _LIBCPP_NO_CFI
# endif # endif
# ifndef _LIBCPP_CXX03_LANG # ifndef _LIBCPP_CXX03_LANG
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