By default, Newlib uses a huge object of type struct _reent to store
thread-specific data. This object is returned by __getreent() if the
__DYNAMIC_REENT__ Newlib configuration option is defined.
The reentrancy structure contains for example errno and the standard input,
output, and error file streams. This means that if an application only uses
errno it has a dependency on the file stream support even if it does not use
it. This is an issue for lower end targets and applications which need to
qualify the software according to safety standards (for example ECSS-E-ST-40C,
ECSS-Q-ST-80C, IEC 61508, ISO 26262, DO-178, DO-330, DO-333).
If the new _REENT_THREAD_LOCAL configuration option is enabled, then struct
_reent is replaced by dedicated thread-local objects for each struct _reent
member. The thread-local objects are defined in translation units which use
the corresponding object.
The _REENT_GLOBAL_STDIO_STREAMS was introduced by commit
668a4c8722 in 2017. Since then it was enabled by
default for RTEMS. Recently, the option was enabled for Cygwin which
previously used an alternative implementation to use global stdio streams.
In Newlib, the stdio streams are defined to thread-specific pointers
_reent::_stdin, _reent::_stdout and _reent::_stderr. If the option is disabled
(the default for most systems), then these pointers are initialized to
thread-specific FILE objects which use file descriptors 0, 1, and 2,
respectively. There are at least three problems with this:
(1) The thread-specific FILE objects are closed by _reclaim_reent(). This
leads to problems with language run-time libraries that provide wrappers to
the C/POSIX stdio streams (for example C++ and Ada), since they use the
thread-specific FILE objects of the initialization thread. In case the
initialization thread is deleted, then they use freed memory.
(2) Since thread-specific FILE objects are used with a common output device via
file descriptors 0, 1 and 2, the locking at FILE object level cannot ensure
atomicity of the output, e.g. a call to printf().
(3) There are resource managment issues, see:
https://sourceware.org/pipermail/newlib/2022/019558.htmlhttps://bugs.linaro.org/show_bug.cgi?id=5841
This patch enables the _REENT_GLOBAL_STDIO_STREAMS behaviour for all Newlib
configurations and removes the option. This removes a couple of #ifdef blocks.
For the exit processing only members of _GLOBAL_REENT were used by default. If
the _REENT_GLOBAL_ATEXIT option was enabled, then the data structures were
provided through dedicated global objects. Make this option the default.
Remove the option. Rename struct _reent members _atexit and _atexit0 to
_reserved_6 and _reserved_7, respectively. Provide them only if
_REENT_BACKWARD_BINARY_COMPAT is defined.
Add the --enable-newlib-reent-binary-compat configure option. This option is
disabled by default. If enabled, then unused members in struct _reent are
preserved to maintain the structure layout.
Replace all of the individual autotool steps with a single autoreconf.
This simplifies the documentation greatly, and in the current system,
only takes ~10 seconds to regenerate everything.
Update the developer documentation to cover all the major components
of the current build system. Hopefully this is a fairly complete road
map to everything. I tried to include everything that I wish I knew
when I started hacking on this :P.
This was added 20+ years ago. It seems to have very few (or no users)
as it only works on 32-bit x86 GNU/Linux (i.e. glibc) systems, and even
then only with old versions of glibc. It hasn't compiled in at least 5
years, but most likely been broken for more like 15 years -- it relies
on internal glibc APIs (like linuxthreads), and that code has changed
and been deleted significantly since.
This single target ends up dragging in a lot of non-trivial code that is
hard to keep working, and currently impossible to verify -- the libtool
and iconvdata and sys/linux/ code isn't used by anything else, but ends
up touching just about every build file in the tree. Punt the target so
we can start stripping out all these unique code paths.
This commit by itself just disables the target. We'll start deleting the
individual unused pieces in followups.
This matches what the other GNU toolchain projects have done already.
The generated diff in practice isn't terribly large. This will allow
more use of subdir local.mk includes due to fixes & improvements that
came after the 1.11 release series.
The 'cygnus' option was removed from automake 1.13 in 2012, so the
presence of this option prevents that or a later version of automake
being used.
A check-list of the effects of '--cygnus' from the automake 1.12
documentation, and steps taken (where possible) to preserve those
effects (See also this thread [1] for discussion on that):
[1] https://lists.gnu.org/archive/html/bug-automake/2012-03/msg00048.html
1. The foreign strictness is implied.
Already present in AM_INIT_AUTOMAKE in newlib/acinclude.m4
2. The options no-installinfo, no-dependencies and no-dist are implied.
Already present in AM_INIT_AUTOMAKE in newlib/acinclude.m4
Future work: Remove no-dependencies and any explicit header dependencies,
and use automatic dependency tracking instead. Are there explicit rules
which are now redundant to removing no-installinfo and no-dist?
3. The macro AM_MAINTAINER_MODE is required.
Already present in newlib/acinclude.m4
Note that maintainer-mode is still disabled by default.
4. Info files are always created in the build directory, and not in the
source directory.
This appears to be an error in the automake documentation describing
'--cygnus' [2]. newlib's info files are generated in the source
directory, and no special steps are needed to keep doing that.
[2] https://lists.gnu.org/archive/html/bug-automake/2012-04/msg00028.html
5. texinfo.tex is not required if a Texinfo source file is specified.
(The assumption is that the file will be supplied, but in a place that
automake cannot find.)
This effect is overriden by an explicit setting of the TEXINFO_TEX
variable (the directory part of which is fed into texi2X via the
TEXINPUTS environment variable).
6. Certain tools will be searched for in the build tree as well as in the
user's PATH. These tools are runtest, expect, makeinfo and texi2dvi.
For obscure automake reasons, this effect of '--cygnus' is not active
for makeinfo in newlib's configury.
However, there appears to be top-level configury which selects in-tree
runtest, expect and makeinfo, if present. So, if that works as it
appears, this effect is preserved. If not, this may cause problem if
anyone is building those tools in-tree.
This effect is not preserved for texi2dvi. This may cause problems if
anyone is building texinfo in-tree.
If needed, explicit checks for those tools looking in places relative to
$(top_srcdir)/../ as well as in PATH could be added.
7. The check target doesn't depend on all.
This effect is not preseved. The check target now depends on the all
target.
This concern seems somewhat academic given the current state of the
testsuite.
Also note that this doesn't touch libgloss.
Use AM_SILENT_RULES, to enable automake silent rules (by default), if we
are using a version of automake which supports it (>=1.11).
Silent rules can be disabled by configuring with '--disable-silent-rules',
or invoking 'make V=1'.
For ease of reviewing, this patch doesn't contain configure and
Makefile.in regeneration.
Future work: There are a few compilations which are not silenced by
this, as they use custom rules.
- This patch uses gdtoa imported from OpenBSD if newlib configure
option "--enable-newlib-use-gdtoa=no" is NOT specified. gdtoa
provides more accurate output and faster conversion than legacy
ldtoa, while it requires more heap memory.
In order to avoid the year 2038 problem, define time_t to a signed
integer with at least 64-bits. The type for time_t can be forced to
long with the --enable-newlib-long-time_t configure option or with the
_USE_LONG_TIME_T system configuration define.
Signed-off-by: Sebastian Huber <sebastian.huber@embedded-brains.de>
Lite exit support.
* README: Add information about lite-exit.
* acconfig.h (_LITE_EXIT): New macro.
* configure.in (enable-lite-exit): New option.
(_LITE_EXIT): Define new macro.
* configure: Regenerated.
* newlib.hin (_LITE_EXIT): New macro.
* libc/stdlib/__atexit.c [_LITE_EXIT]: Add dummy explicit
reference to __call_exitprocs.
* libc/stdlib/cxa_atexit.c [_LITE_EXIT]: Make __register_exitproc a
weak reference.
* libc/stdlib/exit.c (exit)[_LITE_EXIT]: Remove TWS and weakly reference
__call_exitprocs.
Matt Joyce
Sebastian Huber
Mike Frysinger
Jon Turney
Jeff Johnston
Takashi Yano
Konrad Schwarz
Corinna Vinschen
Thomas Fitzsimmons