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glibc/include/features.h
H.J. Lu 6c57d32048 sysconf: Add _SC_MINSIGSTKSZ/_SC_SIGSTKSZ [BZ #20305] 
Add _SC_MINSIGSTKSZ for the minimum signal stack size derived from
AT_MINSIGSTKSZ, which is the minimum number of bytes of free stack
space required in order to gurantee successful, non-nested handling
of a single signal whose handler is an empty function, and _SC_SIGSTKSZ
which is the suggested minimum number of bytes of stack space required
for a signal stack.

If AT_MINSIGSTKSZ isn't available, sysconf (_SC_MINSIGSTKSZ) returns
MINSIGSTKSZ.  On Linux/x86 with XSAVE, the signal frame used by kernel
is composed of the following areas and laid out as:

 ------------------------------
 | alignment padding          |
 ------------------------------
 | xsave buffer               |
 ------------------------------
 | fsave header (32-bit only) |
 ------------------------------
 | siginfo + ucontext         |
 ------------------------------

Compute AT_MINSIGSTKSZ value as size of xsave buffer + size of fsave
header (32-bit only) + size of siginfo and ucontext + alignment padding.

If _SC_SIGSTKSZ_SOURCE or _GNU_SOURCE are defined, MINSIGSTKSZ and SIGSTKSZ
are redefined as

/* Default stack size for a signal handler: sysconf (SC_SIGSTKSZ).  */
 # undef SIGSTKSZ
 # define SIGSTKSZ sysconf (_SC_SIGSTKSZ)

/* Minimum stack size for a signal handler: SIGSTKSZ.  */
 # undef MINSIGSTKSZ
 # define MINSIGSTKSZ SIGSTKSZ

Compilation will fail if the source assumes constant MINSIGSTKSZ or
SIGSTKSZ.

The reason for not simply increasing the kernel's MINSIGSTKSZ #define
(apart from the fact that it is rarely used, due to glibc's shadowing
definitions) was that userspace binaries will have baked in the old
value of the constant and may be making assumptions about it.

For example, the type (char [MINSIGSTKSZ]) changes if this #define
changes.  This could be a problem if an newly built library tries to
memcpy() or dump such an object defined by and old binary.
Bounds-checking and the stack sizes passed to things like sigaltstack()
and makecontext() could similarly go wrong.
2021-02-01 11:00:52 -08:00

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/* Copyright (C) 1991-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#ifndef _FEATURES_H
#define _FEATURES_H 1
/* These are defined by the user (or the compiler)
to specify the desired environment:
__STRICT_ANSI__ ISO Standard C.
_ISOC99_SOURCE Extensions to ISO C89 from ISO C99.
_ISOC11_SOURCE Extensions to ISO C99 from ISO C11.
_ISOC2X_SOURCE Extensions to ISO C99 from ISO C2X.
__STDC_WANT_LIB_EXT2__
Extensions to ISO C99 from TR 27431-2:2010.
__STDC_WANT_IEC_60559_BFP_EXT__
Extensions to ISO C11 from TS 18661-1:2014.
__STDC_WANT_IEC_60559_FUNCS_EXT__
Extensions to ISO C11 from TS 18661-4:2015.
__STDC_WANT_IEC_60559_TYPES_EXT__
Extensions to ISO C11 from TS 18661-3:2015.
_POSIX_SOURCE IEEE Std 1003.1.
_POSIX_C_SOURCE If ==1, like _POSIX_SOURCE; if >=2 add IEEE Std 1003.2;
if >=199309L, add IEEE Std 1003.1b-1993;
if >=199506L, add IEEE Std 1003.1c-1995;
if >=200112L, all of IEEE 1003.1-2004
if >=200809L, all of IEEE 1003.1-2008
_XOPEN_SOURCE Includes POSIX and XPG things. Set to 500 if
Single Unix conformance is wanted, to 600 for the
sixth revision, to 700 for the seventh revision.
_XOPEN_SOURCE_EXTENDED XPG things and X/Open Unix extensions.
_LARGEFILE_SOURCE Some more functions for correct standard I/O.
_LARGEFILE64_SOURCE Additional functionality from LFS for large files.
_FILE_OFFSET_BITS=N Select default filesystem interface.
_ATFILE_SOURCE Additional *at interfaces.
_SC_SIGSTKSZ_SOURCE Select correct (but non compile-time constant)
MINSIGSTKSZ and SIGSTKSZ.
_GNU_SOURCE All of the above, plus GNU extensions.
_DEFAULT_SOURCE The default set of features (taking precedence over
__STRICT_ANSI__).
_FORTIFY_SOURCE Add security hardening to many library functions.
Set to 1 or 2; 2 performs stricter checks than 1.
_REENTRANT, _THREAD_SAFE
Obsolete; equivalent to _POSIX_C_SOURCE=199506L.
The `-ansi' switch to the GNU C compiler, and standards conformance
options such as `-std=c99', define __STRICT_ANSI__. If none of
these are defined, or if _DEFAULT_SOURCE is defined, the default is
to have _POSIX_SOURCE set to one and _POSIX_C_SOURCE set to
200809L, as well as enabling miscellaneous functions from BSD and
SVID. If more than one of these are defined, they accumulate. For
example __STRICT_ANSI__, _POSIX_SOURCE and _POSIX_C_SOURCE together
give you ISO C, 1003.1, and 1003.2, but nothing else.
These are defined by this file and are used by the
header files to decide what to declare or define:
__GLIBC_USE (F) Define things from feature set F. This is defined
to 1 or 0; the subsequent macros are either defined
or undefined, and those tests should be moved to
__GLIBC_USE.
__USE_ISOC11 Define ISO C11 things.
__USE_ISOC99 Define ISO C99 things.
__USE_ISOC95 Define ISO C90 AMD1 (C95) things.
__USE_ISOCXX11 Define ISO C++11 things.
__USE_POSIX Define IEEE Std 1003.1 things.
__USE_POSIX2 Define IEEE Std 1003.2 things.
__USE_POSIX199309 Define IEEE Std 1003.1, and .1b things.
__USE_POSIX199506 Define IEEE Std 1003.1, .1b, .1c and .1i things.
__USE_XOPEN Define XPG things.
__USE_XOPEN_EXTENDED Define X/Open Unix things.
__USE_UNIX98 Define Single Unix V2 things.
__USE_XOPEN2K Define XPG6 things.
__USE_XOPEN2KXSI Define XPG6 XSI things.
__USE_XOPEN2K8 Define XPG7 things.
__USE_XOPEN2K8XSI Define XPG7 XSI things.
__USE_LARGEFILE Define correct standard I/O things.
__USE_LARGEFILE64 Define LFS things with separate names.
__USE_FILE_OFFSET64 Define 64bit interface as default.
__USE_MISC Define things from 4.3BSD or System V Unix.
__USE_ATFILE Define *at interfaces and AT_* constants for them.
__USE_SC_SIGSTKSZ Define correct (but non compile-time constant)
MINSIGSTKSZ and SIGSTKSZ.
__USE_GNU Define GNU extensions.
__USE_FORTIFY_LEVEL Additional security measures used, according to level.
The macros `__GNU_LIBRARY__', `__GLIBC__', and `__GLIBC_MINOR__' are
defined by this file unconditionally. `__GNU_LIBRARY__' is provided
only for compatibility. All new code should use the other symbols
to test for features.
All macros listed above as possibly being defined by this file are
explicitly undefined if they are not explicitly defined.
Feature-test macros that are not defined by the user or compiler
but are implied by the other feature-test macros defined (or by the
lack of any definitions) are defined by the file.
ISO C feature test macros depend on the definition of the macro
when an affected header is included, not when the first system
header is included, and so they are handled in
<bits/libc-header-start.h>, which does not have a multiple include
guard. Feature test macros that can be handled from the first
system header included are handled here. */
/* Undefine everything, so we get a clean slate. */
#undef __USE_ISOC11
#undef __USE_ISOC99
#undef __USE_ISOC95
#undef __USE_ISOCXX11
#undef __USE_POSIX
#undef __USE_POSIX2
#undef __USE_POSIX199309
#undef __USE_POSIX199506
#undef __USE_XOPEN
#undef __USE_XOPEN_EXTENDED
#undef __USE_UNIX98
#undef __USE_XOPEN2K
#undef __USE_XOPEN2KXSI
#undef __USE_XOPEN2K8
#undef __USE_XOPEN2K8XSI
#undef __USE_LARGEFILE
#undef __USE_LARGEFILE64
#undef __USE_FILE_OFFSET64
#undef __USE_MISC
#undef __USE_ATFILE
#undef __USE_SC_SIGSTKSZ
#undef __USE_GNU
#undef __USE_FORTIFY_LEVEL
#undef __KERNEL_STRICT_NAMES
#undef __GLIBC_USE_ISOC2X
#undef __GLIBC_USE_DEPRECATED_GETS
#undef __GLIBC_USE_DEPRECATED_SCANF
/* Suppress kernel-name space pollution unless user expressedly asks
for it. */
#ifndef _LOOSE_KERNEL_NAMES
# define __KERNEL_STRICT_NAMES
#endif
/* Convenience macro to test the version of gcc.
Use like this:
#if __GNUC_PREREQ (2,8)
... code requiring gcc 2.8 or later ...
#endif
Note: only works for GCC 2.0 and later, because __GNUC_MINOR__ was
added in 2.0. */
#if defined __GNUC__ && defined __GNUC_MINOR__
# define __GNUC_PREREQ(maj, min) \
((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
#else
# define __GNUC_PREREQ(maj, min) 0
#endif
/* Similarly for clang. Features added to GCC after version 4.2 may
or may not also be available in clang, and clang's definitions of
__GNUC(_MINOR)__ are fixed at 4 and 2 respectively. Not all such
features can be queried via __has_extension/__has_feature. */
#if defined __clang_major__ && defined __clang_minor__
# define __glibc_clang_prereq(maj, min) \
((__clang_major__ << 16) + __clang_minor__ >= ((maj) << 16) + (min))
#else
# define __glibc_clang_prereq(maj, min) 0
#endif
/* Whether to use feature set F. */
#define __GLIBC_USE(F) __GLIBC_USE_ ## F
/* _BSD_SOURCE and _SVID_SOURCE are deprecated aliases for
_DEFAULT_SOURCE. If _DEFAULT_SOURCE is present we do not
issue a warning; the expectation is that the source is being
transitioned to use the new macro. */
#if (defined _BSD_SOURCE || defined _SVID_SOURCE) \
&& !defined _DEFAULT_SOURCE
# warning "_BSD_SOURCE and _SVID_SOURCE are deprecated, use _DEFAULT_SOURCE"
# undef _DEFAULT_SOURCE
# define _DEFAULT_SOURCE 1
#endif
/* If _GNU_SOURCE was defined by the user, turn on all the other features. */
#ifdef _GNU_SOURCE
# undef _ISOC95_SOURCE
# define _ISOC95_SOURCE 1
# undef _ISOC99_SOURCE
# define _ISOC99_SOURCE 1
# undef _ISOC11_SOURCE
# define _ISOC11_SOURCE 1
# undef _ISOC2X_SOURCE
# define _ISOC2X_SOURCE 1
# undef _POSIX_SOURCE
# define _POSIX_SOURCE 1
# undef _POSIX_C_SOURCE
# define _POSIX_C_SOURCE 200809L
# undef _XOPEN_SOURCE
# define _XOPEN_SOURCE 700
# undef _XOPEN_SOURCE_EXTENDED
# define _XOPEN_SOURCE_EXTENDED 1
# undef _LARGEFILE64_SOURCE
# define _LARGEFILE64_SOURCE 1
# undef _DEFAULT_SOURCE
# define _DEFAULT_SOURCE 1
# undef _ATFILE_SOURCE
# define _ATFILE_SOURCE 1
# undef _SC_SIGSTKSZ_SOURCE
# define _SC_SIGSTKSZ_SOURCE 1
#endif
/* If nothing (other than _GNU_SOURCE and _DEFAULT_SOURCE) is defined,
define _DEFAULT_SOURCE. */
#if (defined _DEFAULT_SOURCE \
|| (!defined __STRICT_ANSI__ \
&& !defined _ISOC99_SOURCE && !defined _ISOC11_SOURCE \
&& !defined _ISOC2X_SOURCE \
&& !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE \
&& !defined _XOPEN_SOURCE))
# undef _DEFAULT_SOURCE
# define _DEFAULT_SOURCE 1
#endif
/* This is to enable the ISO C2X extension. */
#if (defined _ISOC2X_SOURCE \
|| (defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L))
# define __GLIBC_USE_ISOC2X 1
#else
# define __GLIBC_USE_ISOC2X 0
#endif
/* This is to enable the ISO C11 extension. */
#if (defined _ISOC11_SOURCE || defined _ISOC2X_SOURCE \
|| (defined __STDC_VERSION__ && __STDC_VERSION__ >= 201112L))
# define __USE_ISOC11 1
#endif
/* This is to enable the ISO C99 extension. */
#if (defined _ISOC99_SOURCE || defined _ISOC11_SOURCE \
|| defined _ISOC2X_SOURCE \
|| (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L))
# define __USE_ISOC99 1
#endif
/* This is to enable the ISO C90 Amendment 1:1995 extension. */
#if (defined _ISOC99_SOURCE || defined _ISOC11_SOURCE \
|| defined _ISOC2X_SOURCE \
|| (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199409L))
# define __USE_ISOC95 1
#endif
#ifdef __cplusplus
/* This is to enable compatibility for ISO C++17. */
# if __cplusplus >= 201703L
# define __USE_ISOC11 1
# endif
/* This is to enable compatibility for ISO C++11.
Check the temporary macro for now, too. */
# if __cplusplus >= 201103L || defined __GXX_EXPERIMENTAL_CXX0X__
# define __USE_ISOCXX11 1
# define __USE_ISOC99 1
# endif
#endif
/* If none of the ANSI/POSIX macros are defined, or if _DEFAULT_SOURCE
is defined, use POSIX.1-2008 (or another version depending on
_XOPEN_SOURCE). */
#ifdef _DEFAULT_SOURCE
# if !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE
# define __USE_POSIX_IMPLICITLY 1
# endif
# undef _POSIX_SOURCE
# define _POSIX_SOURCE 1
# undef _POSIX_C_SOURCE
# define _POSIX_C_SOURCE 200809L
#endif
#if ((!defined __STRICT_ANSI__ \
|| (defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) >= 500)) \
&& !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE)
# define _POSIX_SOURCE 1
# if defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) < 500
# define _POSIX_C_SOURCE 2
# elif defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) < 600
# define _POSIX_C_SOURCE 199506L
# elif defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) < 700
# define _POSIX_C_SOURCE 200112L
# else
# define _POSIX_C_SOURCE 200809L
# endif
# define __USE_POSIX_IMPLICITLY 1
#endif
/* Some C libraries once required _REENTRANT and/or _THREAD_SAFE to be
defined in all multithreaded code. GNU libc has not required this
for many years. We now treat them as compatibility synonyms for
_POSIX_C_SOURCE=199506L, which is the earliest level of POSIX with
comprehensive support for multithreaded code. Using them never
lowers the selected level of POSIX conformance, only raises it. */
#if ((!defined _POSIX_C_SOURCE || (_POSIX_C_SOURCE - 0) < 199506L) \
&& (defined _REENTRANT || defined _THREAD_SAFE))
# define _POSIX_SOURCE 1
# undef _POSIX_C_SOURCE
# define _POSIX_C_SOURCE 199506L
#endif
#if (defined _POSIX_SOURCE \
|| (defined _POSIX_C_SOURCE && _POSIX_C_SOURCE >= 1) \
|| defined _XOPEN_SOURCE)
# define __USE_POSIX 1
#endif
#if defined _POSIX_C_SOURCE && _POSIX_C_SOURCE >= 2 || defined _XOPEN_SOURCE
# define __USE_POSIX2 1
#endif
#if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 199309L
# define __USE_POSIX199309 1
#endif
#if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 199506L
# define __USE_POSIX199506 1
#endif
#if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 200112L
# define __USE_XOPEN2K 1
# undef __USE_ISOC95
# define __USE_ISOC95 1
# undef __USE_ISOC99
# define __USE_ISOC99 1
#endif
#if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 200809L
# define __USE_XOPEN2K8 1
# undef _ATFILE_SOURCE
# define _ATFILE_SOURCE 1
#endif
#ifdef _XOPEN_SOURCE
# define __USE_XOPEN 1
# if (_XOPEN_SOURCE - 0) >= 500
# define __USE_XOPEN_EXTENDED 1
# define __USE_UNIX98 1
# undef _LARGEFILE_SOURCE
# define _LARGEFILE_SOURCE 1
# if (_XOPEN_SOURCE - 0) >= 600
# if (_XOPEN_SOURCE - 0) >= 700
# define __USE_XOPEN2K8 1
# define __USE_XOPEN2K8XSI 1
# endif
# define __USE_XOPEN2K 1
# define __USE_XOPEN2KXSI 1
# undef __USE_ISOC95
# define __USE_ISOC95 1
# undef __USE_ISOC99
# define __USE_ISOC99 1
# endif
# else
# ifdef _XOPEN_SOURCE_EXTENDED
# define __USE_XOPEN_EXTENDED 1
# endif
# endif
#endif
#ifdef _LARGEFILE_SOURCE
# define __USE_LARGEFILE 1
#endif
#ifdef _LARGEFILE64_SOURCE
# define __USE_LARGEFILE64 1
#endif
#if defined _FILE_OFFSET_BITS && _FILE_OFFSET_BITS == 64
# define __USE_FILE_OFFSET64 1
#endif
#if defined _DEFAULT_SOURCE
# define __USE_MISC 1
#endif
#ifdef _ATFILE_SOURCE
# define __USE_ATFILE 1
#endif
#ifdef _SC_SIGSTKSZ_SOURCE
# define __USE_SC_SIGSTKSZ 1
#endif
#ifdef _GNU_SOURCE
# define __USE_GNU 1
#endif
#if defined _FORTIFY_SOURCE && _FORTIFY_SOURCE > 0
# if !defined __OPTIMIZE__ || __OPTIMIZE__ <= 0
# warning _FORTIFY_SOURCE requires compiling with optimization (-O)
# elif !__GNUC_PREREQ (4, 1)
# warning _FORTIFY_SOURCE requires GCC 4.1 or later
# elif _FORTIFY_SOURCE > 2 && __glibc_clang_prereq (9, 0)
# if _FORTIFY_SOURCE > 3
# warning _FORTIFY_SOURCE > 3 is treated like 3 on this platform
# endif
# define __USE_FORTIFY_LEVEL 3
# elif _FORTIFY_SOURCE > 1
# if _FORTIFY_SOURCE > 2
# warning _FORTIFY_SOURCE > 2 is treated like 2 on this platform
# endif
# define __USE_FORTIFY_LEVEL 2
# else
# define __USE_FORTIFY_LEVEL 1
# endif
#endif
#ifndef __USE_FORTIFY_LEVEL
# define __USE_FORTIFY_LEVEL 0
#endif
/* The function 'gets' existed in C89, but is impossible to use
safely. It has been removed from ISO C11 and ISO C++14. Note: for
compatibility with various implementations of <cstdio>, this test
must consider only the value of __cplusplus when compiling C++. */
#if defined __cplusplus ? __cplusplus >= 201402L : defined __USE_ISOC11
# define __GLIBC_USE_DEPRECATED_GETS 0
#else
# define __GLIBC_USE_DEPRECATED_GETS 1
#endif
/* GNU formerly extended the scanf functions with modified format
specifiers %as, %aS, and %a[...] that allocate a buffer for the
input using malloc. This extension conflicts with ISO C99, which
defines %a as a standalone format specifier that reads a floating-
point number; moreover, POSIX.1-2008 provides the same feature
using the modifier letter 'm' instead (%ms, %mS, %m[...]).
We now follow C99 unless GNU extensions are active and the compiler
is specifically in C89 or C++98 mode (strict or not). For
instance, with GCC, -std=gnu11 will have C99-compliant scanf with
or without -D_GNU_SOURCE, but -std=c89 -D_GNU_SOURCE will have the
old extension. */
#if (defined __USE_GNU \
&& (defined __cplusplus \
? (__cplusplus < 201103L && !defined __GXX_EXPERIMENTAL_CXX0X__) \
: (!defined __STDC_VERSION__ || __STDC_VERSION__ < 199901L)))
# define __GLIBC_USE_DEPRECATED_SCANF 1
#else
# define __GLIBC_USE_DEPRECATED_SCANF 0
#endif
/* Get definitions of __STDC_* predefined macros, if the compiler has
not preincluded this header automatically. */
#include <stdc-predef.h>
/* This macro indicates that the installed library is the GNU C Library.
For historic reasons the value now is 6 and this will stay from now
on. The use of this variable is deprecated. Use __GLIBC__ and
__GLIBC_MINOR__ now (see below) when you want to test for a specific
GNU C library version and use the values in <gnu/lib-names.h> to get
the sonames of the shared libraries. */
#undef __GNU_LIBRARY__
#define __GNU_LIBRARY__ 6
/* Major and minor version number of the GNU C library package. Use
these macros to test for features in specific releases. */
#define __GLIBC__ 2
#define __GLIBC_MINOR__ 33
#define __GLIBC_PREREQ(maj, min) \
((__GLIBC__ << 16) + __GLIBC_MINOR__ >= ((maj) << 16) + (min))
/* This is here only because every header file already includes this one. */
#ifndef __ASSEMBLER__
# ifndef _SYS_CDEFS_H
# include <sys/cdefs.h>
# endif
/* If we don't have __REDIRECT, prototypes will be missing if
__USE_FILE_OFFSET64 but not __USE_LARGEFILE[64]. */
# if defined __USE_FILE_OFFSET64 && !defined __REDIRECT
# define __USE_LARGEFILE 1
# define __USE_LARGEFILE64 1
# endif
#endif /* !ASSEMBLER */
/* Decide whether we can define 'extern inline' functions in headers. */
#if __GNUC_PREREQ (2, 7) && defined __OPTIMIZE__ \
&& !defined __OPTIMIZE_SIZE__ && !defined __NO_INLINE__ \
&& defined __extern_inline
# define __USE_EXTERN_INLINES 1
#endif
/* This is here only because every header file already includes this one.
Get the definitions of all the appropriate `__stub_FUNCTION' symbols.
<gnu/stubs.h> contains `#define __stub_FUNCTION' when FUNCTION is a stub
that will always return failure (and set errno to ENOSYS). */
#include <gnu/stubs.h>
#endif /* features.h */
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