rand(3)'s standard C API is extremely limiting, but we can do better
than the historical 32-bit state Park-Miller LCG we've shipped since
2001: r73156.
The justification provided at the time for not using random(3) was that
rand_r(3) could not be made to use the same algorithm. That is still
true. However, the irrelevance of rand_r(3) is increasingly obvious.
Since that time, POSIX has marked the interface obsolescent. rand_r(3)
never became part of the standard C library. If not for API
compatibility reasons, I would just remove rand_r(3) entirely.
So, I do not believe it is a problem for rand_r(3) and rand(3) to
diverge.
The 12 ABI is maintained with compatibility definitions, but this
revision does subtly change the API of rand(3). The sequences of
pseudorandom numbers produced in programs built against new versions of
libc will differ from programs built against prior versions of libc.
Reviewed by: kevans, markm
MFC after: no
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D23290
to port software written for Linux variant of qsort_r(3).
Reviewed by: kib, arichardson
MFC after: 2 weeks
Relnotes: yes
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D23174
It serves no useful purpose and wasn't as popular as its equally meritless
cousin, srandomdev(3).
Setting aside the problems with rand(3) in general, the problem with this
interface is that the seed isn't shared with the caller (other than by
attacking the output of the generator, which is trivial, but not a hallmark of
pleasant API design). The (arguable) utility of rand(3) or random(3) is as a
semi-fast simulation generator which produces consistent results from a given
seed. These are mutually at odd. Furthermore, sometimes people got the
mistaken impression that a high quality random seed meant a weak generator like
rand(3) or random(3) could be used for things like cryptographic key
generation. This is absolutely not so.
The API was never part of a standard and was not widely used in tree. Existing
in-tree uses have all been removed.
Possible replacement in out of tree codebases:
char buf[3];
time_t t;
time(t);
strftime(buf, sizeof(buf), "%S", gmtime(&t));
srand(atoi(buf));
Relnotes: yes
Since inits for the main binary are run from rtld (for some time), the
rtld_exit atexit(3) handler, which is passed from rtld to the program
entry and installed by csu, is installed after any atexit(3) handlers
installed by main binary constructors. This means that rtld_exit() is
fired before main binary handlers.
Typical C++ static constructors are executed from init (either binary
or libs) but use atexit(3) to ensure that destructors are called in
the right order, independent of the linking order. Also, C++
libraries finalizers call __cxa_finalize(3) to flush library'
atexit(3) entries. Since atexit(3) entry is cleared after being run,
this would be mostly innocent, except that, atexit(rtld_exit) done
after main binary constructors, makes destructors from libraries
executed before destructors for main.
Fix by reordering atexit(rtld_exit) before inits for main binary, same
as it happened when inits were called by csu. Do it using new private
libc symbol with pre-defined ABI.
Reported. tested, and reviewed by: kan
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
9899:2011 Appendix K 3.7.4.1.
Other needed supporting types, defines and constraint_handler
infrastructure is added as specified in the C11 spec.
Submitted by: Tom Rix <trix@juniper.net>
Sponsored by: Juniper Networks
Discussed with: ed
MFC after: 3 weeks
Differential revision: https://reviews.freebsd.org/D9903
Differential revision: https://reviews.freebsd.org/D10161
libstdc++ before gcc r244057 expected that libc provided
__cxa_thread_atexit_impl, and libstdc++ implemented
__cxa_thread_atexit, by forwarding the calls to _impl. Mentioned gcc
revision checks for __cxa_thread_atexit in libc and does not provide
the symbol from libstdc++ if found.
This change helps older gcc, in particular, all released versions
which implement thread_local, by consolidating the implementation into
libc. For that versions, if configured with the current libc, the
__cxa_thread_atexit is exported from libstdc++ as a trivial wrapper
around libc::__cxa_thread_atexit_impl.
The __cxa_thread_atexit implementation is put into separate source
file to allow for static linking with older libstdc++.a.
gcc bugzilla: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78968
Reported by: Hannes Hauswedell <h2+fbsdports@fsfe.org>
PR: 215709
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
This is the backing feature to implement C++11 thread storage duration
specified by the thread_local keyword. A destructor for given
thread-local object is registered to be executed at the thread
termination time using __cxa_thread_atexit(). Libc calls the
__cxa_thread_calls_dtors() during exit(3), before finalizers and
atexit functions, and libthr calls the function at the thread
termination time, after the stack unwinding and thread-specific key
destruction.
There are several uncertainties in the API which lacks a formal
specification. Among them:
- is it allowed to register destructors during destructing;
we allow, but limiting the nesting level. If too many iterations
detected, a diagnostic is issued to stderr and thread forcibly
terminates for now.
- how to handle destructors which belong to an unloading dso;
for now, we ignore destructor calls for such entries, and
issue a diagnostic. Linux does prevent dso unload until all
threads with destructors from the dso terminated.
It is supposed that the diagnostics allow to detect real-world
applications relying on the above details and possibly adjust
our implementation. Right now the choices were to provide the slim
API (but that rarely stands the practice test).
Tests are added to check generic functionality and to specify some of
the above implementation choices.
Submitted by: Mahdi Mokhtari <mokhi64_gmail.com>
Reviewed by: theraven
Discussed with: dim (detection of -std=c++11 supoort for tests)
Sponsored by: The FreeBSD Foundation (my involvement)
MFC after: 2 weeks
Differential revisions: https://reviews.freebsd.org/D7224,
https://reviews.freebsd.org/D7427
Add a manpage for it, assign the copyright to the OpenBSD project on it since it
is mostly copy/paste from OpenBSD manpage.
style(9) fixes
Differential Revision: https://reviews.freebsd.org/D2420
Reviewed by: kib
(or loading a dso linked to libthr.so into process which was not
linked against threading library).
- Remove libthr interposers of the libc functions, including
__error(). Instead, functions calls are indirected through the
interposing table, similar to how pthread stubs in libc are already
done. Libc by default points either to syscall trampolines or to
existing libc implementations. On libthr load, libthr rewrites the
pointers to the cancellable implementations already in libthr. The
interposition table is separate from pthreads stubs indirection
table to not pull pthreads stubs into static binaries.
- Postpone the malloc(3) internal mutexes initialization until libthr
is loaded. This avoids recursion between calloc(3) and static
pthread_mutex_t initialization.
- Reinstall signal handlers with wrapper on libthr load. The
_rtld_is_dlopened(3) is used to avoid useless calls to sigaction(2)
when libthr is statically referenced from the main binary.
In the process, fix openat(2), swapcontext(2) and setcontext(2)
interposing. The libc symbols were exported at different versions
than libthr interposers. Export both libc and libthr versions from
libc now, with default set to the higher version from libthr.
Remove unused and disconnected swapcontext(3) userspace implementation
from libc/gen.
No objections from: deischen
Tested by: pho, antoine (exp-run) (previous versions)
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
bsearch_b is the Apple blocks enabled version of bsearch(3).
This was added to libc in Revision 264042 but the commit
missed the declaration required to make use of it.
While here move some other block-related functions to the
BSD_VISIBLE block as these are non-standard.
Phabric: D638
Reviewed by: theraven, wollman
While testing this I found a conformance issue in hdestroy()
that will be fixed in a subsequent commit.
Obtained from: NetBSD (hcreate.c, CVS Rev. 1.7)
prior to 3.0.0 release) as contrib/jemalloc, and integrate it into libc.
The code being imported by this commit diverged from
lib/libc/stdlib/malloc.c in March 2010, which means that a portion of
the jemalloc 1.0.0 ChangeLog entries are relevant, as are the entries
for all subsequent releases.
The C11 folks reinvented the wheel by introducing an aligned version of
malloc(3) called aligned_alloc(3), instead of posix_memalign(3). Instead
of returning the allocation by reference, it returns the address, just
like malloc(3).
Reviewed by: jasone@
__noreturn macro and modify the other exiting functions to use it.
The __noreturn macro, unlike __dead2, must be used BEFORE the function.
This is in line with the C and C++ specifications that place _Noreturn (c1x)
and [[noreturn]] (C++11) in front of the functions. As with __dead2, this
macro falls back to using the GCC attribute.
Unfortunately, clang currently sets the same value for the C version macro
in C99 and C1x modes, so these functions are hidden by default. At some
point before 10.0, I need to go through the headers and clean up the C1x /
C++11 visibility.
Reviewed by: brooks (mentor)
load of _l suffixed versions of various standard library functions that use
the global locale, making them take an explicit locale parameter. Also
adds support for per-thread locales. This work was funded by the FreeBSD
Foundation.
Please test any code you have that uses the C standard locale functions!
Reviewed by: das (gdtoa changes)
Approved by: dim (mentor)
This caching allows for completely lock-free allocation/deallocation in the
steady state, at the expense of likely increased memory use and
fragmentation.
Reduce the default number of arenas to 2*ncpus, since thread-specific
caching typically reduces arena contention.
Modify size class spacing to include ranges of 2^n-spaced, quantum-spaced,
cacheline-spaced, and subpage-spaced size classes. The advantages are:
fewer size classes, reduced false cacheline sharing, and reduced internal
fragmentation for allocations that are slightly over 512, 1024, etc.
Increase RUN_MAX_SMALL, in order to limit fragmentation for the
subpage-spaced size classes.
Add a size-->bin lookup table for small sizes to simplify translating sizes
to size classes. Include a hard-coded constant table that is used unless
custom size class spacing is specified at run time.
Add the ability to disable tiny size classes at compile time via
MALLOC_TINY.
The last half year I've been working on a replacement TTY layer for the
FreeBSD kernel. The new TTY layer was designed to improve the following:
- Improved driver model:
The old TTY layer has a driver model that is not abstract enough to
make it friendly to use. A good example is the output path, where the
device drivers directly access the output buffers. This means that an
in-kernel PPP implementation must always convert network buffers into
TTY buffers.
If a PPP implementation would be built on top of the new TTY layer
(still needs a hooks layer, though), it would allow the PPP
implementation to directly hand the data to the TTY driver.
- Improved hotplugging:
With the old TTY layer, it isn't entirely safe to destroy TTY's from
the system. This implementation has a two-step destructing design,
where the driver first abandons the TTY. After all threads have left
the TTY, the TTY layer calls a routine in the driver, which can be
used to free resources (unit numbers, etc).
The pts(4) driver also implements this feature, which means
posix_openpt() will now return PTY's that are created on the fly.
- Improved performance:
One of the major improvements is the per-TTY mutex, which is expected
to improve scalability when compared to the old Giant locking.
Another change is the unbuffered copying to userspace, which is both
used on TTY device nodes and PTY masters.
Upgrading should be quite straightforward. Unlike previous versions,
existing kernel configuration files do not need to be changed, except
when they reference device drivers that are listed in UPDATING.
Obtained from: //depot/projects/mpsafetty/...
Approved by: philip (ex-mentor)
Discussed: on the lists, at BSDCan, at the DevSummit
Sponsored by: Snow B.V., the Netherlands
dcons(4) fixed by: kan
The __use_pts() routine was once probably used by libutil to determine
if we are using BSD or UNIX98 style PTY device names. It doesn't seem to
be used outside grantpt.c, which means we can make it static and remove
it from the Symbol.map.
Reviewed by: cognet, kib
Approved by: philip (mentor)
