invalid format strings invoke undefined behavior, so this is not a
conformance issue, but it's nicer for scanf to report the error safely
instead of calling free on a potentially-uninitialized pointer or a
pointer to memory belonging to the caller.
rather than allocating a PATH_MAX-sized buffer when the caller does
not provide an output buffer, work first with a PATH_MAX-sized temp
buffer with automatic storage, and either copy it to the caller's
buffer or strdup it on success. this not only avoids massive memory
waste, but also avoids pulling in free (and thus the full malloc
implementation) unnecessarily in static programs.
this avoids failure if the file is not readable and avoids odd
behavior for device nodes, etc. on old kernels that lack O_PATH, the
old behavior (O_RDONLY) will naturally happen as the fallback.
commit 07827d1a82 seems to have
introduced this issue. sigqueue is called from the synccall core, at
which time, even implementation-internal signals are blocked. however,
pthread_sigmask removes the implementation-internal signals from the
old mask before returning, so that a process which began life with
them blocked will not be able to save a signal mask that has them
blocked, possibly causing them to become re-blocked later. however,
this was causing sigqueue to unblock the implementation-internal
signals during synccall, leading to deadlock.
unlike the old C memcpy, this version handles word-at-a-time reads and
writes even for misaligned copies. it does not require that the cpu
support misaligned accesses; instead, it performs bit shifts to
realign the bytes for the destination.
essentially, this is the C version of the ARM assembly language
memcpy. the ideas are all the same, and it should perform well on any
arch with a decent number of general-purpose registers that has a
barrel shift operation. since the barrel shifter is an optional cpu
feature on microblaze, it may be desirable to provide an alternate asm
implementation on microblaze, but otherwise the C code provides a
competitive implementation for "generic risc-y" cpu archs that should
alleviate the urgent need for arch-specific memcpy asm.
this version of memset is optimized both for small and large values of
n, and makes no misaligned writes, so it is usable (and near-optimal)
on all archs. it is capable of filling up to 52 or 56 bytes without
entering a loop and with at most 7 branches, all of which can be fully
predicted if memset is called multiple times with the same size.
it also uses the attribute extension to inform the compiler that it is
violating the aliasing rules, unlike the previous code which simply
assumed it was safe to violate the aliasing rules since translation
unit boundaries hide the violations from the compiler. for non-GNUC
compilers, 100% portable fallback code in the form of a naive loop is
provided. I intend to eventually apply this approach to all of the
string/memory functions which are doing word-at-a-time accesses.
this is a nonstandard extension but will be required in the next
version of POSIX, and it's widely used/useful in shell scripts
utilizing the date utility.
this may need further revision in the future, since POSIX is rather
unclear on the requirements, and is designed around the assumption of
POSIX TZ specifiers which are not sufficiently powerful to represent
real-world timezones (this is why zoneinfo support was added).
the basic issue is that strftime gets the string and numeric offset
for the timezone from the extra fields in struct tm, which are
initialized when calling localtime/gmtime/etc. however, a conforming
application might have created its own struct tm without initializing
these fields, in which case using __tm_zone (a pointer) could crash.
other zoneinfo-based implementations simply check for a null pointer,
but otherwise can still crash of the field contains junk.
simply ignoring __tm_zone and using tzname[] would "work" but would
give incorrect results in time zones with more complex rules. I feel
like this would lower the quality of implementation.
instead, simply validate __tm_zone: unless it points to one of the
zone name strings managed by the timezone system, assume it's invalid.
this commit also fixes several other minor bugs with formatting:
tm_isdst being negative is required to suppress printing of the zone
formats, and %z was using the wrong format specifiers since the type
of val was changed, resulting in bogus output.
the empty TZ string was matching equal to the initial value of the
cached TZ name, thus causing do_tzset never to run and never to
initialize the time zone data.
1. an occurrence of ${ORIGIN} before $ORIGIN would be ignored due to
the strstr logic. (note that rpath contains multiple :-delimited paths
to be searched.)
2. data read by readlink was not null-terminated.
fallback to argv[0] as before. unlike argv[0], AT_EXECFN was a valid
(but possibly relative) pathname for the new program image at the time
the execve syscall was made.
as a special case, ignore AT_EXECFN if it begins with "/proc/", in
order not to give bogus (and possibly harmful) results when fexecve
was used.
previously, rpath was only honored for direct dependencies. in other
words, if A depends on B and B depends on C, only B's rpath (if any),
not A's rpath, was being searched for C. this limitation made
rpath-based deployment difficult in the presence of multiple levels of
library dependency.
at present, $ORIGIN processing in rpath is still unsupported.
at present, since POSIX requires %F to behave as %+4Y-%m-%d and ISO C
requires %F to behave as %Y-%m-%d, the default behavior for %Y has
been changed to match %+4Y. this seems to be the only way to conform
to the requirements of both standards, and it does not affect years
prior to the year 10000. depending on the outcome of interpretations
from the standards bodies, this may be adjusted at some point.
use a long long value so that even with offsets, values cannot
overflow. instead of using different format strings for different
numeric formats, simply use a per-format width and %0*lld for all of
them.
this width specifier is not for use with strftime field widths; that
will be a separate step in the caller.
make __strftime_fmt_1 return a string (possibly in the caller-provided
temp buffer) rather than writing into the output buffer. this approach
makes more sense when padding to a minimum field width might be
required, and it's also closer to what wcsftime wants.
fesetround.c is a wrapper to do the arch independent argument
check (on archs where rounding mode is not stored in 2 bits
__fesetround still has to check its arguments)
on powerpc fe*except functions do not accept the extra invalid
flags of its fpscr register
the useless FENV_ACCESS pragma was removed from feupdateenv
the x87 exception summary (ES) and stack fault (SF) flags may be
spuriously cleared by feclearexcept using the fnclex instruction,
but these flags are not observable through libc hence maintaining
their state is not critical.
the sse and x87 rounding modes should be always the same,
the visible exception flags are the bitwise or of the two
fenv states (so it's enough to query the rounding mode or
raise exceptions on one fenv)
with these changes, the character set implemented as "big5" in musl is
a pure superset of cp950, the canonical "big5", and agrees with the
normative parts of Unicode. this means it has minor differences from
both hkscs and big5-2003:
- the range A2CC-A2CE maps to CJK ideographs rather than numerals,
contrary to changes made in big5-2003.
- C6CD maps to a CJK ideograph rather than its corresponding Kangxi
radical character, contrary to changes made in hkscs.
- F9FE maps to U+2593 rather than U+FFED.
of these differences, none but the last are visually distinct, and the
last is a character used purely for text-based graphics, not to convey
linguistic content.
should there be future demand for strict conformance to big5-2003 or
hkscs mappings, the present charset aliases can be replaced with
distinct variants.
reportedly there are other non-standard big5 extensions in common use
in Taiwan and perhaps elsewhere, which could also be added as layers
on top of the existing big5 support.
there may be additional characters which should be added to the hkscs
table: the whatwg standard for big5 defines what appears to be a
superset of hkscs.
if FLT_EVAL_METHOD!=0 check if (double)(1/x) is subnormal and not a
power of 2 (if 1/x is power of 2 then either it is exact or the
long double to double rounding already raised inexact and underflow)
* remove volatile hacks
* don't care about inexact flag for now (removed all the +-tiny)
* fix atanl to raise underflow properly
* remove signed int arithmetics
* use pi/2 instead of pi_o_2 (gcc generates the same code, which is not
correct, but it does not matter: we mainly care about nearest rounding)
underflow is raised by an inexact subnormal float store,
since subnormal operations are slow, check the underflow
flag and skip the store if it's already raised
for these functions f(x)=x for small inputs, because f(0)=0 and
f'(0)=1, but for subnormal values they should raise the underflow
flag (required by annex F), if they are approximated by a polynomial
around 0 then spurious underflow should be avoided (not required by
annex F)
all these functions should raise inexact flag for small x if x!=0,
but it's not required by the standard and it does not seem a worthy
goal, so support for it is removed in some cases.
raising underflow:
- x*x may not raise underflow for subnormal x if FLT_EVAL_METHOD!=0
- x*x may raise spurious underflow for normal x if FLT_EVAL_METHOD==0
- in case of double subnormal x, store x as float
- in case of float subnormal x, store x*x as float
there are two possible points where the length is evaluated: either
the first 'compression' jump, or the null terminator if no jumps have
taken place yet. the previous code only measured the length of the
first component.
the duplicate code in dn_expand and its incorrect return values are
both results of the history of the code: the version in __dns.c was
originally written with no awareness of the legacy resolver API, and
was later copy-and-paste duplicated to provide the legacy API.
this commit is the first of a series that will restructure the
internal dns code to share as much code as possible with the legacy
resolver API functions.
I have also removed the loop detection logic, since the output buffer
length limit naturally prevents loops. in order to avoid long runtime
when encountering a loop if the caller provided a ridiculously long
buffer, the caller-provided length is clamped at the maximum dns name
length.
the approach of this implementation was heavily investigated prior to
adopting it. attempts to obtain similar performance with pure C code
were capping out at about 75% of the performance of the asm, with
considerably larger code size, and were fragile in that the compiler
would sometimes compile part of memcpy into a call to itself.
therefore, just using the asm seems to be the best option.
this commit is the first to make use of the new subarch-specific asm
framework. the new armel directory is the location for arm asm that
should not be used for all arm subarchs, only the default one. armhf
is the name of the little-endian hardfloat-ABI subarch, which can use
the exact same asm. in both cases, the build system finds the asm by
following a memcpy.sub file.
the other two subarchs, armeb and armebhf, would need a big-endian
variant of this code. it would not be hard to adapt the code to big
endian, but I will hold off on doing so until there is demand for it.
a mips signal mask contains 128 bits, enough for signals 1 through
128. however, the exit status obtained from the wait-family functions
only has room for values up to 127. reportedly signal 128 was causing
kernelspace bugs, so it was removed from the kernel recently; even
without that issue, however, it was impossible to support it correctly
in userspace.
at the same time, the bug was masked on musl by SIGRTMAX incorrectly
yielding 64 on mips, rather than the "correct" value of 128. now that
the _NSIG issue is fixed, SIGRTMAX can be fixed at the same time,
exposing the full range of signals for application use.
note that the (nonstandardized) libc _NSIG value is actually one
greater than the max signal number, and also one greater than the
kernel headers' idea of _NSIG. this is the reason for the discrepency
with the recent kernel changes. since reducing _NSIG by one brought it
down from 129 to 128, rather than from 128 to 127, _NSIG/8, used
widely in the musl sources, is unchanged.
Rich Felker