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https://sourceware.org/git/binutils-gdb.git
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aca8a74923
Since we now require C++17, and therefore gcc >= 9, it's no longer useful to have gcc version checks for older gcc version. Change-Id: I3a87baa03c475f2b847b422b16b69c5ff7215b54 Reviewed-by: Kevin Buettner <kevinb@redhat.com> Approved-By: Pedro Alves <pedro@palves.net>
221 lines
7.0 KiB
C
221 lines
7.0 KiB
C
/* Common definitions.
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Copyright (C) 1986-2024 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef COMMON_COMMON_DEFS_H
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#define COMMON_COMMON_DEFS_H
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#include <gdbsupport/config.h>
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#undef PACKAGE_NAME
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#undef PACKAGE
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#undef PACKAGE_VERSION
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#undef PACKAGE_STRING
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#undef PACKAGE_TARNAME
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#include "gnulib/config.h"
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/* From:
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https://www.gnu.org/software/gnulib/manual/html_node/stdint_002eh.html
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"On some hosts that predate C++11, when using C++ one must define
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__STDC_CONSTANT_MACROS to make visible the definitions of constant
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macros such as INTMAX_C, and one must define __STDC_LIMIT_MACROS to
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make visible the definitions of limit macros such as INTMAX_MAX.".
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And:
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https://www.gnu.org/software/gnulib/manual/html_node/inttypes_002eh.html
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"On some hosts that predate C++11, when using C++ one must define
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__STDC_FORMAT_MACROS to make visible the declarations of format
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macros such as PRIdMAX."
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Must do this before including any system header, since other system
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headers may include stdint.h/inttypes.h. */
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#define __STDC_CONSTANT_MACROS 1
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#define __STDC_LIMIT_MACROS 1
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#define __STDC_FORMAT_MACROS 1
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/* Some distros enable _FORTIFY_SOURCE by default, which on occasion
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has caused build failures with -Wunused-result when a patch is
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developed on a distro that does not enable _FORTIFY_SOURCE. We
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enable it here in order to try to catch these problems earlier;
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plus this seems like a reasonable safety measure. The check for
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optimization is required because _FORTIFY_SOURCE only works when
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optimization is enabled. If _FORTIFY_SOURCE is already defined,
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then we don't do anything. Also, on MinGW, fortify requires
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linking to -lssp, and to avoid the hassle of checking for
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that and linking to it statically, we just don't define
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_FORTIFY_SOURCE there. */
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#if (!defined _FORTIFY_SOURCE && defined __OPTIMIZE__ && __OPTIMIZE__ > 0 \
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&& !defined(__MINGW32__))
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#define _FORTIFY_SOURCE 2
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#endif
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/* We don't support Windows versions before XP, so we define
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_WIN32_WINNT correspondingly to ensure the Windows API headers
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expose the required symbols.
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NOTE: this must be kept in sync with common.m4. */
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#if defined (__MINGW32__) || defined (__CYGWIN__)
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# ifdef _WIN32_WINNT
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# if _WIN32_WINNT < 0x0501
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# undef _WIN32_WINNT
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# define _WIN32_WINNT 0x0501
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# endif
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# else
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# define _WIN32_WINNT 0x0501
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# endif
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#endif /* __MINGW32__ || __CYGWIN__ */
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#include <stdarg.h>
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#include <stdio.h>
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/* Include both cstdlib and stdlib.h to ensure we have standard functions
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defined both in the std:: namespace and in the global namespace. */
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#include <cstdlib>
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#include <stdlib.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <string.h>
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#ifdef HAVE_STRINGS_H
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#include <strings.h>
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#endif
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#include <errno.h>
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#if HAVE_ALLOCA_H
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#include <alloca.h>
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#endif
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#include "ansidecl.h"
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/* This is defined by ansidecl.h, but we prefer gnulib's version. On
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MinGW, gnulib might enable __USE_MINGW_ANSI_STDIO, which may or not
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require use of attribute gnu_printf instead of printf. gnulib
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checks that at configure time. Since _GL_ATTRIBUTE_FORMAT_PRINTF_STANDARD
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is compatible with ATTRIBUTE_PRINTF, simply use it. */
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#undef ATTRIBUTE_PRINTF
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#define ATTRIBUTE_PRINTF _GL_ATTRIBUTE_FORMAT_PRINTF_STANDARD
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/* This is defined by ansidecl.h, but we disable the attribute.
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Say a developer starts out with:
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...
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extern void foo (void *ptr) __attribute__((nonnull (1)));
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void foo (void *ptr) {}
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...
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with the idea in mind to catch:
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...
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foo (nullptr);
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...
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at compile time with -Werror=nonnull, and then adds:
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...
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void foo (void *ptr) {
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+ gdb_assert (ptr != nullptr);
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}
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...
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to catch:
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...
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foo (variable_with_nullptr_value);
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...
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at runtime as well.
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Said developer then verifies that the assert works (using -O0), and commits
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the code.
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Some other developer then checks out the code and accidentally writes some
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variant of:
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...
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foo (variable_with_nullptr_value);
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...
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and builds with -O2, and ... the assert doesn't trigger, because it's
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optimized away by gcc.
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There's no suppported recipe to prevent the assertion from being optimized
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away (other than: build with -O0, or remove the nonnull attribute). Note
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that -fno-delete-null-pointer-checks does not help. A patch was submitted
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to improve gcc documentation to point this out more clearly (
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https://gcc.gnu.org/pipermail/gcc-patches/2021-July/576218.html ). The
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patch also mentions a possible workaround that obfuscates the pointer
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using:
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...
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void foo (void *ptr) {
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+ asm ("" : "+r"(ptr));
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gdb_assert (ptr != nullptr);
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}
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...
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but that still requires the developer to manually add this in all cases
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where that's necessary.
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A warning was added to detect the situation: -Wnonnull-compare, which does
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help in detecting those cases, but each new gcc release may indicate a new
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batch of locations that needs fixing, which means we've added a maintenance
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burden.
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We could try to deal with the problem more proactively by introducing a
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gdb_assert variant like:
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...
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void gdb_assert_non_null (void *ptr) {
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asm ("" : "+r"(ptr));
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gdb_assert (ptr != nullptr);
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}
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void foo (void *ptr) {
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gdb_assert_nonnull (ptr);
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}
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...
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and make it a coding style to use it everywhere, but again, maintenance
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burden.
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With all these things considered, for now we go with the solution with the
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least maintenance burden: disable the attribute, such that we reliably deal
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with it everywhere. */
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#undef ATTRIBUTE_NONNULL
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#define ATTRIBUTE_NONNULL(m)
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#define ATTRIBUTE_UNUSED_RESULT __attribute__ ((__warn_unused_result__))
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#define ATTRIBUTE_USED __attribute__ ((__used__))
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#include "libiberty.h"
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#include "pathmax.h"
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#include "gdb/signals.h"
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#include "gdb_locale.h"
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#include "ptid.h"
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#include "common-types.h"
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#include "common-utils.h"
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#include "gdb_assert.h"
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#include "errors.h"
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#include "print-utils.h"
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#include "common-debug.h"
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#include "cleanups.h"
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#include "common-exceptions.h"
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#include "gdbsupport/poison.h"
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/* Pull in gdb::unique_xmalloc_ptr. */
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#include "gdbsupport/gdb_unique_ptr.h"
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/* sbrk on macOS is not useful for our purposes, since sbrk(0) always
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returns the same value. brk/sbrk on macOS is just an emulation
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that always returns a pointer to a 4MB section reserved for
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that. */
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#if defined (HAVE_SBRK) && !__APPLE__
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#define HAVE_USEFUL_SBRK 1
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#endif
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#endif /* COMMON_COMMON_DEFS_H */
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