1/* Common definitions.
2
3   Copyright (C) 1986-2020 Free Software Foundation, Inc.
4
5   This file is part of GDB.
6
7   This program is free software; you can redistribute it and/or modify
8   it under the terms of the GNU General Public License as published by
9   the Free Software Foundation; either version 3 of the License, or
10   (at your option) any later version.
11
12   This program is distributed in the hope that it will be useful,
13   but WITHOUT ANY WARRANTY; without even the implied warranty of
14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15   GNU General Public License for more details.
16
17   You should have received a copy of the GNU General Public License
18   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
19
20#ifndef COMMON_COMMON_DEFS_H
21#define COMMON_COMMON_DEFS_H
22
23#include <gdbsupport/config.h>
24
25#undef PACKAGE_NAME
26#undef PACKAGE
27#undef PACKAGE_VERSION
28#undef PACKAGE_STRING
29#undef PACKAGE_TARNAME
30
31#include "gnulib/config.h"
32
33/* From:
34    https://www.gnu.org/software/gnulib/manual/html_node/stdint_002eh.html
35
36   "On some hosts that predate C++11, when using C++ one must define
37   __STDC_CONSTANT_MACROS to make visible the definitions of constant
38   macros such as INTMAX_C, and one must define __STDC_LIMIT_MACROS to
39   make visible the definitions of limit macros such as INTMAX_MAX.".
40
41   And:
42    https://www.gnu.org/software/gnulib/manual/html_node/inttypes_002eh.html
43
44   "On some hosts that predate C++11, when using C++ one must define
45   __STDC_FORMAT_MACROS to make visible the declarations of format
46   macros such as PRIdMAX."
47
48   Must do this before including any system header, since other system
49   headers may include stdint.h/inttypes.h.  */
50#define __STDC_CONSTANT_MACROS 1
51#define __STDC_LIMIT_MACROS 1
52#define __STDC_FORMAT_MACROS 1
53
54/* Some distros enable _FORTIFY_SOURCE by default, which on occasion
55   has caused build failures with -Wunused-result when a patch is
56   developed on a distro that does not enable _FORTIFY_SOURCE.  We
57   enable it here in order to try to catch these problems earlier;
58   plus this seems like a reasonable safety measure.  The check for
59   optimization is required because _FORTIFY_SOURCE only works when
60   optimization is enabled.  If _FORTIFY_SOURCE is already defined,
61   then we don't do anything.  Also, on MinGW, fortify requires
62   linking to -lssp, and to avoid the hassle of checking for
63   that and linking to it statically, we just don't define
64   _FORTIFY_SOURCE there.  */
65
66#if (!defined _FORTIFY_SOURCE && defined __OPTIMIZE__ && __OPTIMIZE__ > 0 \
67     && !defined(__MINGW32__))
68#define _FORTIFY_SOURCE 2
69#endif
70
71/* We don't support Windows versions before XP, so we define
72   _WIN32_WINNT correspondingly to ensure the Windows API headers
73   expose the required symbols.  */
74#if defined (__MINGW32__) || defined (__CYGWIN__)
75# ifdef _WIN32_WINNT
76#  if _WIN32_WINNT < 0x0501
77#   undef _WIN32_WINNT
78#   define _WIN32_WINNT 0x0501
79#  endif
80# else
81#  define _WIN32_WINNT 0x0501
82# endif
83#endif	/* __MINGW32__ || __CYGWIN__ */
84
85#include <stdarg.h>
86#include <stdio.h>
87
88/* Include both cstdlib and stdlib.h to ensure we have standard functions
89   defined both in the std:: namespace and in the global namespace.  */
90#include <cstdlib>
91#include <stdlib.h>
92
93#include <stddef.h>
94#include <stdint.h>
95#include <string.h>
96#ifdef HAVE_STRINGS_H
97#include <strings.h>	/* for strcasecmp and strncasecmp */
98#endif
99#include <errno.h>
100#if HAVE_ALLOCA_H
101#include <alloca.h>
102#endif
103
104#include "ansidecl.h"
105/* This is defined by ansidecl.h, but we prefer gnulib's version.  On
106   MinGW, gnulib might enable __USE_MINGW_ANSI_STDIO, which may or not
107   require use of attribute gnu_printf instead of printf.  gnulib
108   checks that at configure time.  Since _GL_ATTRIBUTE_FORMAT_PRINTF
109   is compatible with ATTRIBUTE_PRINTF, simply use it.  */
110#undef ATTRIBUTE_PRINTF
111#define ATTRIBUTE_PRINTF _GL_ATTRIBUTE_FORMAT_PRINTF
112
113/* This is defined by ansidecl.h, but we disable the attribute.
114
115   Say a developer starts out with:
116   ...
117   extern void foo (void *ptr) __atttribute__((nonnull (1)));
118   void foo (void *ptr) {}
119   ...
120   with the idea in mind to catch:
121   ...
122   foo (nullptr);
123   ...
124   at compile time with -Werror=nonnull, and then adds:
125   ...
126    void foo (void *ptr) {
127   +  gdb_assert (ptr != nullptr);
128    }
129   ...
130   to catch:
131   ...
132   foo (variable_with_nullptr_value);
133   ...
134   at runtime as well.
135
136   Said developer then verifies that the assert works (using -O0), and commits
137   the code.
138
139   Some other developer then checks out the code and accidentally writes some
140   variant of:
141   ...
142   foo (variable_with_nullptr_value);
143   ...
144   and builds with -O2, and ... the assert doesn't trigger, because it's
145   optimized away by gcc.
146
147   There's no suppported recipe to prevent the assertion from being optimized
148   away (other than: build with -O0, or remove the nonnull attribute).  Note
149   that -fno-delete-null-pointer-checks does not help.  A patch was submitted
150   to improve gcc documentation to point this out more clearly (
151   https://gcc.gnu.org/pipermail/gcc-patches/2021-July/576218.html ).  The
152   patch also mentions a possible workaround that obfuscates the pointer
153   using:
154   ...
155    void foo (void *ptr) {
156   +  asm ("" : "+r"(ptr));
157      gdb_assert (ptr != nullptr);
158    }
159   ...
160   but that still requires the developer to manually add this in all cases
161   where that's necessary.
162
163   A warning was added to detect the situation: -Wnonnull-compare, which does
164   help in detecting those cases, but each new gcc release may indicate a new
165   batch of locations that needs fixing, which means we've added a maintenance
166   burden.
167
168   We could try to deal with the problem more proactively by introducing a
169   gdb_assert variant like:
170   ...
171   void gdb_assert_non_null (void *ptr) {
172      asm ("" : "+r"(ptr));
173      gdb_assert (ptr != nullptr);
174    }
175    void foo (void *ptr) {
176      gdb_assert_nonnull (ptr);
177    }
178   ...
179   and make it a coding style to use it everywhere, but again, maintenance
180   burden.
181
182   With all these things considered, for now we go with the solution with the
183   least maintenance burden: disable the attribute, such that we reliably deal
184   with it everywhere.  */
185#undef ATTRIBUTE_NONNULL
186#define ATTRIBUTE_NONNULL(m)
187
188#if GCC_VERSION >= 3004
189#define ATTRIBUTE_UNUSED_RESULT __attribute__ ((__warn_unused_result__))
190#else
191#define ATTRIBUTE_UNUSED_RESULT
192#endif
193
194#include "libiberty.h"
195#include "pathmax.h"
196#include "gdb/signals.h"
197#include "gdb_locale.h"
198#include "ptid.h"
199#include "common-types.h"
200#include "common-utils.h"
201#include "gdb_assert.h"
202#include "errors.h"
203#include "print-utils.h"
204#include "common-debug.h"
205#include "cleanups.h"
206#include "common-exceptions.h"
207#include "gdbsupport/poison.h"
208
209#define EXTERN_C extern "C"
210#define EXTERN_C_PUSH extern "C" {
211#define EXTERN_C_POP }
212
213/* Pull in gdb::unique_xmalloc_ptr.  */
214#include "gdbsupport/gdb_unique_ptr.h"
215
216/* String containing the current directory (what getwd would return).  */
217extern char *current_directory;
218
219/* sbrk on macOS is not useful for our purposes, since sbrk(0) always
220   returns the same value.  brk/sbrk on macOS is just an emulation
221   that always returns a pointer to a 4MB section reserved for
222   that.  */
223
224#if defined (HAVE_SBRK) && !__APPLE__
225#define HAVE_USEFUL_SBRK 1
226#endif
227
228#endif /* COMMON_COMMON_DEFS_H */
229