this was messed up during a recent commit when the socketcall macros
were moved to the common internal/syscall.h, and the following commit
expanded the problem by adding more new content outside the guard.

this only matters on x32 (and perhaps future 32-on-64 abis for other
archs); otherwise the type is long anyway. the cast through uintptr_t
prevents nonsensical "sign extension" of pointers, and follows the
principle that uintptr_t is the canonical integer type to which
pointer conversion is safe.

open is handled specially because it is used from so many places, in
so many variants (2 or 3 arguments, setting errno or not, and
cancellable or not). trying to do it as a function would not only
increase bloat, but would also risk subtle breakage.

this is the first step towards supporting "new" archs where linux
lacks "old" syscalls.

the main motivation for this change is that, with the previous
definition, it was arguably illegal, in standard C, to initialize both
si_value and si_pid/si_uid with designated initializers, due to the
rule that only one member of a union can have an initializer. whether
or not this affected real-world application code, it affected some
internal code, and clang was producing warnings (and possibly
generating incorrect code).

the new definition uses a more complex hierarchy of structs and unions
to avoid the need to initialize more than one member of a single union
in usage cases that make sense. further work would be needed to
eliminate even the ones with no practical applications.

at the same time, some fixes are made to the exposed names for
nonstandard fields, to match what software using them expects.

%C, %U, %W, and %y handling were completely missing; %C wrongly
fell-through to unrelated cases, and the rest returned failure. for
now, they all parse numbers in the proper forms and range-check the
values, but they do not store the value anywhere.

it's not clear to me whether, as "derived" fields, %U and %W should
produce any result. they certainly cannot produce a result unless the
year and weekday are also converted, but in this case it might be
desirable for them to do so. clarification is needed on the intended
behavior of strptime in cases like this.

%C and %y have well-defined behavior as long as they are used together
(and %y is defined by itself but may change in the future).
implementing them (including their correct interaction) is left as a
later change to be made.

finally, strptime now rejects unknown/invalid format characters
instead of ignoring them.

some of these may have been from ancient (pre-SUSv2) POSIX versions;
more likely, they were from POSIX drafts or glibc interpretations of
what ancient versions of POSIX should have added (instead they made
they described functionality mandatory and/or dropped it completely).
others are purely glibc-isms, many of them ill-thought-out, like
providing ways to lookup the min/max values of types at runtime
(despite the impossibility of them changing at runtime and the
impossibility of representing ULONG_MAX in a return value of type
long).

since our sysconf implementation does not support or return meaningful
values for any of these, it's harmful to have the macros around;
applications' build scripts may detect and attempt to use them, only
to get -1/EINVAL as a result.

if removing them does break some applications, and it's determined
that the usage was reasonable, some of these could be added back on an
as-needed basis, but they should return actual meaningful values, not
junk like they were returning before.

based on patch by Timo Teräs. previously, the value zero was used as a
literal zero, meaning that all invalid sysconf "names", which should
result in sysconf returning -1, had to be explicitly listed. (in
addition, it was not possible for sysconf to set errno to EINVAL, as
there was no distinction between -1 as an error and -1 as a valid
result.)

now, the value 0 is used for invalid/undefined slots in the table and
a new switch table entry is used for returning literal zeros.

in addition, an off-by-one error in checking against the table size is
fixed.

this is gcc bug #61144. the broken compiler is detected, but the user
must manually work around it. this is partly to avoid complex logic
for adding workaround CFLAGS and attempting to recheck with them, and
partly for the sake of letting the user know the compiler is broken
(since the workaround will result in less-efficient code production).

some refactoring was also needed to move the check for gcc outside of
the check for whether to build the compiler wrapper.

perhaps some additional legacy DOS-era codepages would also be useful
to have, but these are the ones for which there has been demand. the
size of the diff is due to the fact that legacychars.h is updated in
such a way that new characters are inserted into the table in unicode
codepoint order; thus other mappings in codepages.h have changed to
reflect the new table indices of their characters.

without this, broken choices of CC/CPPFLAGS/CFLAGS don't show up until
late in the configure process where they are confusingly reported as a
different failure such as incorrect long double type.

this is no longer used for anything, and reportedly clashed with a
builtin on certain compilers.

armv7/thumb2 provides a way to do atomics in thumb mode, but for armv6
we need a call to arm mode.

this commit is based on a patch by Stephen Thomas which fixed the
armv7 cases but not the armv6 ones.

all of this should be revisited if/when runtime selection of thread
pointer access and atomics are added.

As far as gcc3 knows, sh4 is the only processor version that can have an
FPU, so it indicates the FPU's presence by defining __SH4__.  This is not
defined if there is no FPU, even if the processor really is an SH4.

Starting with gcc4, there is support for the sh2a processor, which has an
FPU but is not an SH4.  gcc4 therefore additionally defines __SH_FPU_ANY__
when there is an FPU, but still doesn't define __SH4__ for an FPU-less sh4.

Therefore, to support all gcc versions, we must look at both preprocessor
symbols.

previously, setting TZ to the pathname of a file which was not a valid
zoneinfo file would usually cause programs using local time zone based
operations to crash. the new code checks the file size and magic at
the beginning of the file, which seems sufficient to prevent
accidental misconfiguration from causing crashes. attempting to make
fully-robust validation would be futile unless we wanted to drop use
of mmap (shared zoneinfo) and instead read it into a local buffer,
since such validation would be subject to race conditions with
modification of the file.

being static allows it to be inlined in __libc_start_main; inlining
should take place at all levels since the function is called exactly
once. this further reduces mandatory startup code size for static
binaries.

there is no reason (and seemingly there never was any) for
__init_security to be its own function. it's linked unconditionally
so it can just be placed inline in __init_libc.

moving the call to __init_ssp from __init_security to __init_libc
makes __init_security a leaf function, which allows the compiler to
make it smaller. __init_libc is already non-leaf, and the additional
call makes no difference to the amount of register spillage.

in addition, it really made no sense for the call to __init_ssp to be
buried inside __init_security rather than parallel with other init
functions.

since the form TZ=name is reserved for POSIX-form time zone strings,
TZ=:name needs to be used when the zoneinfo filename is in the
top-level zoneinfo directory and therefore does not contain a slash.
previously the leading colon was merely dropped, making it impossible
to access such zones without a full absolute pathname.

changes based on patch by Timo Teräs.

in cases where the memorized match range from the right factor
exceeded the length of the left factor, it was wrongly treated as a
mismatch rather than a match.

issue reported by Yves Bastide.

so far the options are --library-path and --preload which override the
corresponding environment variables, and --list which forces the
behavior of ldd even if the invocation name is not ldd. both the
two-arg form and the one-arg form using an equals sign are supported.

based loosely on a patch proposed by Rune.

the vdso symbol lookup code is based on the original 2011 patch by
Nicholas J. Kain, with some streamlining, pointer arithmetic fixes,
and one symbol version matching fix.

on the consumer side (clock_gettime), per-arch macros for the
particular symbol name and version to lookup are added in
syscall_arch.h, and no vdso code is pulled in on archs which do not
define these macros. at this time, vdso is enabled only on x86_64.

the vdso support at the dynamic linker level is no longer useful to
libc, but is left in place for the sake of debuggers (which may need
the vdso in the link map to find its functions) and possibly use with
dlsym.

at the end of successful pthread_once, there was a race window during
which another thread calling pthread_once would momentarily change the
state back from 2 (finished) to 1 (in-progress). in this case, the
status was immediately changed back, but with no wake call, meaning
that waiters which arrived during this short window could block
forever. there are two possible fixes. one would be adding the wake to
the code path where it was missing. but it's better just to avoid
reverting the status at all, by using compare-and-swap instead of
swap.

The mips arch is special in that it uses different RLIMIT_
numbers than other archs, so allow bits/resource.h to override
the default RLIMIT_ numbers (empty on all archs except mips).
Reported by orc.

it will be needed to implement some things in sysconf, and the syscall
can't easily be used directly because the x32 syscall uses the wrong
structure layout. the l (uncreative, for "linux") prefix is used since
the symbol name __sysinfo is already taken for AT_SYSINFO from the aux
vector.

the way the x32 override of this function works is also changed to be
simpler and avoid the useless jump instruction.

the syscall is deprecated (replaced by prlimit64) and does not work
correctly on x32. this change mildly increases size, but is likely
needed anyway for newer archs that might omit deprecated syscalls.

the previous handling of cases that could not fit in the 16-bit table
or which required non-constant results was extremely ugly and could
not scale. the new code remaps these keys into a contiguous range
that's efficient for a switch statement.

aside from potentially offering better performance, this change is
needed since the old coprocessor-based approach to barriers is
deprecated in arm v7, and some compilers/assemblers issue errors when
using the deprecated instruction for v7 targets.

the use of visibility at all is purely an optimization to avoid the
need for the caller to load the GOT register or similar to prepare for
a call via the PLT. there is no reason for these symbols to be
externally visible, so hidden works just as well as protected, and
using protected visibility is undesirable due to toolchain bugs and
the lack of testing it receives.

in particular, GCC's microblaze target is known to generate symbolic
relocations in the GOT for functions with protected visibility. this
in turn results in a dynamic linker which crashes under any nontrivial
usage that requires making a syscall before symbolic relocations are
processed.

modfl and sincosl were passing long double* instead of double*
to the wrapped double precision functions (on archs where long
double and double have the same size).
This is fixed now by using temporaries (this is not optimized
to a single branch so the generated code is a bit bigger).
Found by Morten Welinder.

to optimize the search, memchr is used to find the first occurrence of
the first character of the needle in the haystack before switching to
a search for the full needle. however, the number of characters
skipped by this first step were not subtracted from the haystack
length, causing memmem to search past the end of the haystack.