The gilbc manual has some documentation in llio.texi of requirements
for moving between I/O on FILE * streams and file descriptors on the
same open file description.
The documentation of what must be done on a FILE * stream to move from
it to either a file descriptor or another FILE * for the same open
file description seems to match POSIX. However, there is an
additional requirement in POSIX on the *second* of the two handles
being moved between, which is not mentioned in the glibc manual: "If
any previous active handle has been used by a function that explicitly
changed the file offset, except as required above for the first
handle, the application shall perform an lseek() or fseek() (as
appropriate to the type of handle) to an appropriate location.".
Document this requirement on seeking in the glibc manual, limited to
the case that seems relevant to glibc (the new channel is a previously
active stream, on which the seeking previously occurred). Note that
I'm not sure what the "except as required above for the first handle"
is meant to be about, so I haven't documented anything for it. As far
as I can tell, nothing specified for moving from the first handle
actually list calling a seek function as one of the steps to be done.
(Current POSIX doesn't seem to have any relevant rationale for this
section. The rationale in the 1996 edition says "In requiring the
seek to an appropriate location for the new handle, the application is
required to know what it is doing if it is passing streams with seeks
involved. If the required seek is not done, the results are undefined
(and in fact the program probably will not work on many common
implementations)." - which also doesn't help in understanding the
purpose of "except as required above for the first handle".)
Tested with "make info" and "make pdf".
Glibc has two gnu-extension functions that are implemented as
macros but not documented as such: fread_unlocked and
fwrite_unlocked. Document them as such.
Additionally, putc_unlocked and getc_unlocked are documented in
POSIX as possibly being macros. Update the manual to add a warning
about those also, depite glibc not implementing them as macros.
The manual contained several instances of incorrect formatting
that were correct texinfo but produced incorrectly rendered manuals
or incorrect behaviour from the tooling.
The most important was incorrect quoting of function returns
by failing to use {} to quote the return. The impact of this
mistake means that 'info libc func' does not jump to the function
in question but instead to the introductory page under the assumption
that func doesn't exist. The function returns are now correctly
quoted.
The second issue was the use of a category specifier with
@deftypefun which doesn't accept a category specifier. If a category
specifier is required then @deftypefn needs to be used. This is
corrected by changing the command to @deftypefn for such functions
that used {Deprecated function} as a category.
The last issue is a missing space between the function name and the
arguments which results in odd function names like "epoll_wait(int"
instead of "epoll_wait". This also impacts the use of 'info libc'
and is corrected.
We additionally remove ';' from the end of function arguments and
add an 'int' return type for dprintf.
Lastly we add a new test check-deftype.sh which verifies the expected
formatting of @deftypefun, @deftypefunx, @deftypefn, and
@deftypefnx. The new test is also run as the summary file is
generated to ensure we don't generate incorrect results.
The existing check-safety.sh is also run directly as a test to increase
coverage since the existing tests only ran on manual install.
The new tests now run as part of the standard "make check" that
pre-commit CI runs and developers should run.
No regressions on x86_64.
HTML and PDF rendering reviewed and looks correct for all changes.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
Linux 6.11 adds the new flag for pwritev2 (commit
c34fc6f26ab86d03a2d47446f42b6cd492dfdc56).
Checked on x86_64-linux-gnu on 6.11 kernel.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
This request the page to be never written out to swap, it will be zeroed
under memory pressure (so kernel can just drop the page), it is inherited
by fork, it is not counted against @code{mlock} budget, and if there is
no enough memory to service a page faults there is no fatal error (so not
signal is sent).
Tested with build-many-glibcs.py.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
The recursive lock used on abort does not synchronize with a new process
creation (either by fork-like interfaces or posix_spawn ones), nor it
is reinitialized after fork().
Also, the SIGABRT unblock before raise() shows another race condition,
where a fork or posix_spawn() call by another thread, just after the
recursive lock release and before the SIGABRT signal, might create
programs with a non-expected signal mask. With the default option
(without POSIX_SPAWN_SETSIGDEF), the process can see SIG_DFL for
SIGABRT, where it should be SIG_IGN.
To fix the AS-safe, raise() does not change the process signal mask,
and an AS-safe lock is used if a SIGABRT is installed or the process
is blocked or ignored. With the signal mask change removal,
there is no need to use a recursive loc. The lock is also taken on
both _Fork() and posix_spawn(), to avoid the spawn process to see the
abort handler as SIG_DFL.
A read-write lock is used to avoid serialize _Fork and posix_spawn
execution. Both sigaction (SIGABRT) and abort() requires to lock
as writer (since both change the disposition).
The fallback is also simplified: there is no need to use a loop of
ABORT_INSTRUCTION after _exit() (if the syscall does not terminate the
process, the system is broken).
The proposed fix changes how setjmp works on a SIGABRT handler, where
glibc does not save the signal mask. So usage like the below will now
always abort.
static volatile int chk_fail_ok;
static jmp_buf chk_fail_buf;
static void
handler (int sig)
{
if (chk_fail_ok)
{
chk_fail_ok = 0;
longjmp (chk_fail_buf, 1);
}
else
_exit (127);
}
[...]
signal (SIGABRT, handler);
[....]
chk_fail_ok = 1;
if (! setjmp (chk_fail_buf))
{
// Something that can calls abort, like a failed fortify function.
chk_fail_ok = 0;
printf ("FAIL\n");
}
Such cases will need to use sigsetjmp instead.
The _dl_start_profile calls sigaction through _profil, and to avoid
pulling abort() on loader the call is replaced with __libc_sigaction.
Checked on x86_64-linux-gnu and aarch64-linux-gnu.
Reviewed-by: DJ Delorie <dj@redhat.com>
This is not completely clear from the C standard (although there
is footnote number 289 in C11), but I assume that our implementation
works this way.
Reviewed-by: DJ Delorie <dj@redhat.com>
The __is_last field was replaced with a bitmask in
commit 85830c4c46 in 2000,
and multiple bits are in use today.
Reviewed-by: DJ Delorie <dj@redhat.com>
And struct sched_attr.
In sysdeps/unix/sysv/linux/bits/sched.h, the hack that defines
sched_param around the inclusion of <linux/sched/types.h> is quite
ugly, but the definition of struct sched_param has already been
dropped by the kernel, so there is nothing else we can do and maintain
compatibility of <sched.h> with a wide range of kernel header
versions. (An alternative would involve introducing a separate header
for this functionality, but this seems unnecessary.)
The existing sched_* functions that change scheduler parameters
are already incompatible with PTHREAD_PRIO_PROTECT mutexes, so
there is no harm in adding more functionality in this area.
The documentation mostly defers to the Linux manual pages.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
From the existing @manpagefunctionstub{func,sec} macro,
so that URLs can be included in the manual without the
stub text.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
As recently discussed, document that freopen does not work with
streams opened with functions such as popen, fmemopen, open_memstream
or fopencookie. I've filed
<https://austingroupbugs.net/view.php?id=1855> to clarify this issue
in POSIX.
Tested with "make info" and "make html".
Reference this new section from the O_PATH documentation.
And document the functions openat, openat64, fstatat, fstatat64.
(The safety assessment for fstatat was already obsolete because
current glibc assumes kernel support for the underlying system
call.)
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
When ungetc is called on an unused stream, the backup buffer is
allocated without the main get area being present. This results in
every subsequent ungetc (as the stream remains in the backup area)
checking uninitialized memory in the backup buffer when trying to put a
character back into the stream.
Avoid comparing the input character with buffer contents when in backup
to avoid this uninitialized read. The uninitialized read is harmless in
this context since the location is promptly overwritten with the input
character, thus fulfilling ungetc functionality.
Also adjust wording in the manual to drop the paragraph that says glibc
cannot do multiple ungetc back to back since with this change, ungetc
can actually do this.
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This is a follow-up to 10de4a47ef that
reworded the manual entries for putc and putwc and removed any
performance claims.
This commit further clarifies these entries and brings getc and getwc in
line with the descriptions of putc and putwc, removing any performance
claims from them as well.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
The existing description for setrlimit() has some ambiguity. It could be
understood to have the semantics of getrlimit(), i.e., the limits from the
process are stored in the provided rlp pointer.
Make the description more explicit that rlp are the input values, and that
the limits of the process is changed with this function.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
The manual entry for `putc' described what "most systems" do instead of
describing the glibc implementation and its guarantees. This commit
fixes that by warning that putc may be implemented as a macro that
double-evaluates `stream', and removing the performance claim.
Even though the current `putc' implementation does not double-evaluate
`stream', offering this obscure guarantee as an extension to what
POSIX allows does not seem very useful.
The entry for `putwc' is also edited to bring it in line with `putc'.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
The __rseq_size value is now the active area of struct rseq
(so 20 initially), not the full struct size including padding
at the end (32 initially).
Update misc/tst-rseq to print some additional diagnostics.
Reviewed-by: Michael Jeanson <mjeanson@efficios.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
The purpose of this patch is to add some system calls that (1) aren't
otherwise documented, and (2) are merely redirected to the kernel, so
can refer to their documentation; and define a standard way of doing
so in the future. A more detailed explaination of how system calls
are wrapped is added along with reference to the Linux Man-Pages
project.
Default version of man-pages is in configure.ac but can be overridden
by --with-man-pages=X.Y
Reviewed-by: Alejandro Colomar <alx@kernel.org>
This new section in the manual provides recommendations for
use of glibc in environments with higher integrity requirements.
It's reflecting both current implementation shortcomings, and
challenges we inherit from ELF and psABI requirements.
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
By default, if the C++ toolchain lacks support for static linking,
configure fails to find the C++ header files and the glibc build fails.
The --disable-static-c++-link-check option allows the glibc build to
finish, but static C++ tests will fail if the C++ toolchain doesn't
have the necessary static C++ libraries which may not be easily installed.
Add --disable-static-c++-tests option to skip the static C++ link check
and tests. This fixes BZ #31797.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
The current minimum GCC version of glibc build is GCC 6.2 or newer. But
building i686 glibc with GCC 6.4 on Fedora 40 failed since the C++ header
files couldn't be found which was caused by the static C++ link check
failure due to missing __divmoddi4 which was referenced in i686 libc.a
and added to GCC 7. Add --disable-static-c++-link-check configure option
to disable the static C++ link test. The newly built i686 libc.a can be
used by GCC 6.4 to create static C++ tests. This fixes BZ #31412.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Extend the list of MAP_* macros to include all macros available
to the average program (gcc -E -dM | grep MAP_*)
Extend the list of errno codes.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
* manual/string.texi: For strnlen (s, maxlen), do not say that s must
be of size maxlen, as it can be smaller if it is null-terminated.
This should help avoid confusion such as seen in
<https://lists.gnu.org/r/bug-gnulib/2024-06/msg00280.html>.
Mention that strnlen and wcsnlen have been in POSIX since
POSIX.1-2008.
Remove the environment variable LD_HWCAP_MASK and the tunable
glibc.cpu.hwcap_mask as those are not used anymore in common-code
after removal in elf/dl-cache.c:search_cache().
The only remaining user is sparc32 where it is used in
elf_machine_matches_host(). If sparc32 does not need it anymore,
we can get rid of it at all. Otherwise we could also move
LD_HWCAP_MASK / tunable glibc.cpu.hwcap_mask to be sparc32 specific.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
As discussed at the patch review meeting
Signed-off-by: Andreas K. Hüttel <dilfridge@gentoo.org>
Reviewed-by: Simon Chopin <simon.chopin@canonical.com>
C23 adds various <math.h> function families originally defined in TS
18661-4. Add the exp2m1 and exp10m1 functions (exp2(x)-1 and
exp10(x)-1, like expm1).
As with other such functions, these use type-generic templates that
could be replaced with faster and more accurate type-specific
implementations in future. Test inputs are copied from those for
expm1, plus some additions close to the overflow threshold (copied
from exp2 and exp10) and also some near the underflow threshold.
exp2m1 has the unusual property of having an input (M_MAX_EXP) where
whether the function overflows (under IEEE semantics) depends on the
rounding mode. Although these could reasonably be XFAILed in the
testsuite (as we do in some cases for arguments very close to a
function's overflow threshold when an error of a few ulps in the
implementation can result in the implementation not agreeing with an
ideal one on whether overflow takes place - the testsuite isn't smart
enough to handle this automatically), since these functions aren't
required to be correctly rounding, I made the implementation check for
and handle this case specially.
The Makefile ordering expected by lint-makefiles for the new functions
is a bit peculiar, but I implemented it in this patch so that the test
passes; I don't know why log2 also needed moving in one Makefile
variable setting when it didn't in my previous patches, but the
failure showed a different place was expected for that function as
well.
The powerpc64le IFUNC setup seems not to be as self-contained as one
might hope; it shouldn't be necessary to add IFUNCs for new functions
such as these simply to get them building, but without setting up
IFUNCs for the new functions, there were undefined references to
__GI___expm1f128 (that IFUNC machinery results in no such function
being defined, but doesn't stop include/math.h from doing the
redirection resulting in the exp2m1f128 and exp10m1f128
implementations expecting to call it).
Tested for x86_64 and x86, and with build-many-glibcs.py.
C23 adds various <math.h> function families originally defined in TS
18661-4. Add the log10p1 functions (log10(1+x): like log1p, but for
base-10 logarithms).
This is directly analogous to the log2p1 implementation (except that
whereas log2p1 has a smaller underflow range than log1p, log10p1 has a
larger underflow range). The test inputs are copied from those for
log1p and log2p1, plus a few more inputs in that wider underflow
range.
Tested for x86_64 and x86, and with build-many-glibcs.py.
C23 adds various <math.h> function families originally defined in TS
18661-4. Add the logp1 functions (aliases for log1p functions - the
name is intended to be more consistent with the new log2p1 and
log10p1, where clearly it would have been very confusing to name those
functions log21p and log101p). As aliases rather than new functions,
the content of this patch is somewhat different from those actually
adding new functions.
Tests are shared with log1p, so this patch *does* mechanically update
all affected libm-test-ulps files to expect the same errors for both
functions.
The vector versions of log1p on aarch64 and x86_64 are *not* updated
to have logp1 aliases (and thus there are no corresponding header,
tests, abilist or ulps changes for vector functions either). It would
be reasonable for such vector aliases and corresponding changes to
other files to be made separately. For now, the log1p tests instead
avoid testing logp1 in the vector case (a Makefile change is needed to
avoid problems with grep, used in generating the .c files for vector
function tests, matching more than one ALL_RM_TEST line in a file
testing multiple functions with the same inputs, when it assumes that
the .inc file only has a single such line).
Tested for x86_64 and x86, and with build-many-glibcs.py.
POSIX.1-2024 (now official) specifies tm_gmtoff and tm_zone.
This is a good time to update the manual’s “Date and Time”
chapter so I went through it, fixed some outdated
stuff that had been in there for decades, and improved it to match
POSIX.1-2024 better and to clarify some implementation-defined
behavior. Glibc already conforms to POSIX.1-2024 in these matters, so
this is merely a documentation change.
* manual/examples/strftim.c: Use snprintf instead of now-deprecated
function asctime. Check for localtime failure. Simplify by using
puts instead of fputs. Prefer ‘buf, sizeof buf’ to less-obvious
‘buffer, SIZE’.
* manual/examples/timespec_subtract.c: Modernize to use struct
timespec not struct timeval, and rename from timeval_subtract.c.
All uses changed. Check for overflow. Do not check for negative
return value, which ought to be OK since negative time_t is OK.
Use GNU indenting style.
* manual/time.texi:
Document CLOCKS_PER_SEC, TIME_UTC, timespec_get, timespec_getres,
strftime_l.
Document the storage lifetime of tm_zone and of tzname.
Caution against use of tzname, timezone and daylight, saying that
these variables have unspecified values when TZ is geographic.
This is what glibc actually does (contrary to what the manual said
before this patch), and POSIX is planned to say the same thing
<https://austingroupbugs.net/view.php?id=1816>.
Also say that directly accessing the variables is not thread-safe.
Say that localtime_r and ctime_r don’t necessarily set time zone
state. Similarly, in the tzset documentation, say that it is called
by ctime, localtime, mktime, strftime, not that it is called by all
time conversion functions that depend on the time zone.
Say that tm_isdst is useful mostly just for mktime, and that
other uses should prefer tm_gmtoff and tm_zone instead.
Do not say that strftime ignores tm_gmtoff and tm_zone, because
it doesn’t do that.
Document what gmtime does to tm_gmtoff and tm_zone.
Say that the asctime, asctime_r, ctime, and ctime_r are now deprecated
and/or obsolescent, and that behavior is undefined if the year is <
1000 or > 9999. Document strftime before these now-obsolescent
functions, so that readers see the useful function first.
Coin the terms “geographical format” and “proleptic format” for the
two main formats of TZ settings, to simplify exposition. Use this
wording consistently.
Update top-level proleptic syntax to match POSIX.1-2024, which glibc
already implements. Document the angle-bracket quoted forms of time
zone abbreviations in proleptic TZ. Say that time zone abbreviations
can contain only ASCII alphanumerics, ‘+’, and ‘-’.
Document what happens if the proleptic form specifies a DST
abbreviation and offset but omits the rules. POSIX says this is
implementation-defined so we need to document it. Although this
documentation mentions ‘posixrules’ tersely, we need to rethink
‘posixrules’ since I think it stops working after 2038.
Clarify wording about TZ settings beginning with ‘;’.
Say that timegm is in ISO C (as of C23).
Say that POSIX.1-2024 removed gettimeofday.
Say that tm_gmtoff and tm_zone are extensions to ISO C, which is
clearer than saying they are invisible in a struct ISO C enviroment,
and gives us more wiggle room if we want to make them visible in
strict ISO C, something that ISO C allows.
Drop mention of old standards like POSIX.1c and POSIX.2-1992 in the
text when the history is so old that it’s no longer useful in a
general-purpose manual.
Define Coordinated Universal Time (UTC), time zone, time zone ruleset,
and POSIX Epoch, and use these phrases more consistently.
Improve TZ examples to show more variety, and to reflect current
practice and timestamps. Remove obsolete example about Argentina.
Add an example for Ireland.
Don’t rely on GCC extensions when explaining ctime_r.
Do not say that difftime produces the mathematically correct result,
since it might be inexact.
For clock_t don’t say “as in the example above” when there is no
such example, and don’t say that casting to double works “properly
and consistently no matter what”, as it suffers from rounding and
overflow.
Don’t say broken-down time is not useful for calculations; it’s
merely painful.
Say that UTC is not defined before 1960.
Rename Time Zone Functions to Time Zone State. All uses changed.
Update Internet RFC 822 → 5322, 1305 → 5905. Drop specific years of
ISO 8601 as they don’t matter.
Minor style changes: @code{"..."} → @t{"..."} to avoid overquoting in
info files, @code → @env for environment variables, Daylight Saving
Time → daylight saving time, white space → whitespace, prime meridian
→ Prime Meridian.
The tuning for non-temporal stores for memset vs memcpy is not always
the same. This includes both the exact value and whether non-temporal
stores are profitable at all for a given arch.
This patch add `x86_memset_non_temporal_threshold`. Currently we
disable non-temporal stores for non Intel vendors as the only
benchmarks showing its benefit have been on Intel hardware.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
C23 adds various <math.h> function families originally defined in TS
18661-4. Add the log2p1 functions (log2(1+x): like log1p, but for
base-2 logarithms).
This illustrates the intended structure of implementations of all
these function families: define them initially with a type-generic
template implementation. If someone wishes to add type-specific
implementations, it is likely such implementations can be both faster
and more accurate than the type-generic one and can then override it
for types for which they are implemented (adding benchmarks would be
desirable in such cases to demonstrate that a new implementation is
indeed faster).
The test inputs are copied from those for log1p. Note that these
changes make gen-auto-libm-tests depend on MPFR 4.2 (or later).
The bulk of the changes are fairly generic for any such new function.
(sysdeps/powerpc/nofpu/Makefile only needs changing for those
type-generic templates that use fabs.)
Tested for x86_64 and x86, and with build-many-glibcs.py.
The current IFUNC selection is always using the most recent
features which are available via AT_HWCAP. But in
some scenarios it is useful to adjust this selection.
The environment variable:
GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,zzz,....
can be used to enable HWCAP feature yyy, disable HWCAP feature xxx,
where the feature name is case-sensitive and has to match the ones
used in sysdeps/loongarch/cpu-tunables.c.
Signed-off-by: caiyinyu <caiyinyu@loongson.cn>
This prints some information from struct cpu_features, and the midr_el1
and dczid_el0 system register contents on every CPU.
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
This is surprisingly difficult to implement if the goal is to produce
reasonably sized output. With the current approaches to output
compression (suppressing zeros and repeated results between CPUs,
folding ranges of identical subleaves, dealing with the %ecx
reflection issue), the output is less than 600 KiB even for systems
with 256 logical CPUs.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
* manual/search.texi (Array Search Function):
Correct the statement about lfind’s mean runtime:
it is proportional to a number (not that number),
and this is true only if random elements are searched for.
Relax the constraint on bsearch’s array argument:
POSIX says it need not be sorted, only partially sorted.
Say that the first arg passed to bsearch’s comparison function
is the key, and the second arg is an array element, as
POSIX requires. For bsearch and qsort, say that the
comparison function should not alter the array, as POSIX
requires. For qsort, say that the comparison function
must define a total order, as POSIX requires, that
it should not depend on element addresses, that
the original array index can be used for stable sorts,
and that if qsort still works if memory allocation fails.
Be more consistent in calling the array elements
“elements” rather than “objects”.
Co-authored-by: Zack Weinberg <zack@owlfolio.org>
In Linux 6.9 a new flag is added to allow for Per-io operations to
disable append mode even if a file was opened with the flag O_APPEND.
This is done with the new RWF_NOAPPEND flag.
This caused two test failures as these tests expected the flag 0x00000020
to be unused. Adding the flag definition now fixes these tests on Linux
6.9 (v6.9-rc1).
FAIL: misc/tst-preadvwritev2
FAIL: misc/tst-preadvwritev64v2
This patch adds the flag, adjusts the test and adds details to
documentation.
Link: https://lore.kernel.org/all/20200831153207.GO3265@brightrain.aerifal.cx/
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
