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.
Add a _REENT_SIG_FUNC() macro to encapsulate access to the
_sig_func member of struct reent. This will help to replace the
struct member with a thread-local storage object in a follow up
patch.
Add a _REENT_CVTBUF() macro to encapsulate access to the _cvtbuf
member of struct reent. This will help to replace the struct
member with a thread-local storage object in a follow up patch.
Add a _REENT_CLEANUP() macro to encapsulate access to the
__cleanup member of struct reent. This will help to replace the
struct member with a thread-local storage object in a follow up
patch.
Use this macro to access the _emergency member of struct _reent. This macro
will help to replace the _emergency member of struct _reent with a thread-local
storage object in a follow up patch.
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.
Remove dependency on __sdidinit member of struct _reent to check
object initialization. Like __sdidinit, the __cleanup member of
struct _reent is initialized in the __sinit() function. Checking
initialization against __cleanup serves the same purpose and will
reduce overhead in the __sfp() function in a follow up patch.
* libc/include/sys/config.h (_REENT_GLOBAL_ATEXIT): Define for
RTEMS.
* libc/include/sys/reent.h (_reent): Use _REENT_GLOBAL_ATEXIT.
(_global_atexit): Declare if _REENT_GLOBAL_ATEXIT is defined.
* libc/reent/reent.c (_reclaim_reent): Remove atexit cleanup if
_REENT_GLOBAL_ATEXIT is defined.
(_wrapup_reent): Remove atexit handling if _REENT_GLOBAL_ATEXIT
is defined.
* libc/stdlib/__atexit.c (_global_atexit0): Define if
_REENT_GLOBAL_ATEXIT is defined.
* libc/stdlib/__call_atexit.c (_global_atexit): Define if
_REENT_GLOBAL_ATEXIT is defined.
* libc/include/sys/reent.h (_Kmax): Define here based on the sizeof
size_t, as in latest NetBSD.
* libc/reent/reent.c (_reclaim_reent): Use _Kmax rather than constant
value 15.
* libc/stdlib/mprec.c (_Kmax): Don't define here. Explain why.
statements in _REENT_SMALL case. Check if _atexit is not NULL before
dereferencing it.
(_wrapup_reent): Check if _atexit is not NULL before dereferencing it.
Allow building internal stubs for non-reentrant syscalls
if target provides its own malloc
* libc/reent/reent.c (errno): Move definition here.
* libc/reent/sbrkr.c: From here.
* libc/stdlib/mprec.c (ulp, b2d, d2b): changed a few expressions
like x << y-z to the equivalent x << (y-z).
(d2b): changed if statements with assignment to perform the
assignment prior to the if check.
* libc/reent/reent.c: included stdlib.h for "_free_r" prototype.
* libc/unix/getpass.c (getpass): moved "echo" assignment out of if.
* libc/unix/ttyname.c: included string.h for "strcpy" prototype.
* libc/unix/getcwd.c (ISDOT): added parentheses to clarify && and ||
precedence.
* libc/include/sys/unistd.h: added "vfork" prototype (for popen.c).
Added "_execve" prototype (for execl.c, execle.c, execv.c, and
execve.c).
* libc/posix/popen.c (popen): added parentheses to clarify && and ||
precedence.
* libm/math/e_cosh.c (__ieee754_cosh): changed parentheses to
clarify && and || precendence (and to remove pascalism).
* libm/math/e_sinh.c (__ieee754_sinh): Ditto.
* libm/math/s_infconst.c: added another pair of braces to all
initializers for __infinity (need three: for __infinity[1] array,
for union __dmath, and for i[2]).
Matt Joyce
Sebastian Huber
Yaakov Selkowitz
Corinna Vinschen
Jeff Johnston
Nick Clifton
Matthew Green
Christopher Faylor