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this change is motivated by the intersection of several factors.
presently, despite being a nonstandard header, endian.h is exposing
the unprefixed byte order macros and functions only if _BSD_SOURCE or
_GNU_SOURCE is defined. this is to accommodate use of endian.h from
other headers, including bits headers, which need to define structure
layout in terms of endianness. with time64 switch-over, even more
headers will need to do this.
at the same time, the resolution of Austin Group issue 162 makes
endian.h a standard header for POSIX-future, requiring that it expose
the unprefixed macros and the functions even in standards-conforming
profiles. changes to meet this new requirement would break existing
internal usage of endian.h by causing it to violate namespace where
it's used.
instead, have the arch's alltypes.h define __BYTE_ORDER, either as a
fixed constant or depending on the right arch-specific predefined
macros for determining endianness. explicit literals 1234 and 4321 are
used instead of __LITTLE_ENDIAN and __BIG_ENDIAN so that there's no
danger of getting the wrong result if a macro is undefined and
implicitly evaluates to 0 at the preprocessor level.
the powerpc (32-bit) bits/endian.h being removed had logic for varying
endianness, but our powerpc arch has never supported that and has
always been big-endian-only. this logic is not carried over to the new
__BYTE_ORDER definition in alltypes.h.
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now that commit f7f1079796abc6f97c69521d2334e9c7d3945dd8 removed the
legacy i386 conditional definition, va_list is in no way
arch-specific, and has no reason to be in the future. move it to the
shared part of alltypes.h.in
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historically, a number of 32-bit archs used long rather than int for
wchar_t, for no good reason. GCC still uses the historical types, but
clang replaced them all with int, and it seems PCC uses int too.
mismatching the compiler's type for wchar_t is not an option due to
wide string literals.
note that the mismatch does not affect C++ ABI since wchar_t is its
own builtin type/keyword in C++, distinct from both int and long, not
a typedef.
i386 already worked around this by honoring __WCHAR_TYPE__ if defined
by the compiler, and only using the official legacy ABI type if not.
add the same to the other affected archs.
it might make sense at some point to switch to using int as the
default if __WCHAR_TYPE__ is not defined, if the expectations is that
new compilers will treat int as the correct choice, but it's unlikely
that the case where __WCHAR_TYPE__ is undefined will ever be used
anyway. I actually wanted to move the definition of wchar_t to the
top-level shared alltypes.h.in, using __WCHAR_TYPE__ and falling back
to int if not defined, but that can't be done without assuming all
compilers define __WCHAR_TYPE__ thanks to some pathological archs
where the ABI has wchar_t as an unsigned type.
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three ABIs are supported: the default with 68881 80-bit fpu format and
results returned in floating point registers, softfloat-only with the
same format, and coldfire fpu with IEEE single/double only. only the
first is tested at all, and only under qemu which has fpu emulation
bugs.
basic functionality smoke tests have been performed for the most
common arch-specific breakage via libc-test and qemu user-level
emulation. some sysvipc failures remain, but are shared with other big
endian archs and will be fixed separately.
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