1 /* Common definitions. 2 3 Copyright (C) 1986-2024 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 75 NOTE: this must be kept in sync with common.m4. */ 76 #if defined (__MINGW32__) || defined (__CYGWIN__) 77 # ifdef _WIN32_WINNT 78 # if _WIN32_WINNT < 0x0501 79 # undef _WIN32_WINNT 80 # define _WIN32_WINNT 0x0501 81 # endif 82 # else 83 # define _WIN32_WINNT 0x0501 84 # endif 85 #endif /* __MINGW32__ || __CYGWIN__ */ 86 87 #include <stdarg.h> 88 #include <stdio.h> 89 90 /* Include both cstdlib and stdlib.h to ensure we have standard functions 91 defined both in the std:: namespace and in the global namespace. */ 92 #include <cstdlib> 93 #include <stdlib.h> 94 95 #include <stddef.h> 96 #include <stdint.h> 97 #include <string.h> 98 #ifdef HAVE_STRINGS_H 99 #include <strings.h> 100 #endif 101 #include <errno.h> 102 #if HAVE_ALLOCA_H 103 #include <alloca.h> 104 #endif 105 106 #include "ansidecl.h" 107 /* This is defined by ansidecl.h, but we prefer gnulib's version. On 108 MinGW, gnulib might enable __USE_MINGW_ANSI_STDIO, which may or not 109 require use of attribute gnu_printf instead of printf. gnulib 110 checks that at configure time. Since _GL_ATTRIBUTE_FORMAT_PRINTF_STANDARD 111 is compatible with ATTRIBUTE_PRINTF, simply use it. */ 112 #undef ATTRIBUTE_PRINTF 113 #define ATTRIBUTE_PRINTF _GL_ATTRIBUTE_FORMAT_PRINTF_STANDARD 114 115 /* This is defined by ansidecl.h, but we disable the attribute. 116 117 Say a developer starts out with: 118 ... 119 extern void foo (void *ptr) __attribute__((nonnull (1))); 120 void foo (void *ptr) {} 121 ... 122 with the idea in mind to catch: 123 ... 124 foo (nullptr); 125 ... 126 at compile time with -Werror=nonnull, and then adds: 127 ... 128 void foo (void *ptr) { 129 + gdb_assert (ptr != nullptr); 130 } 131 ... 132 to catch: 133 ... 134 foo (variable_with_nullptr_value); 135 ... 136 at runtime as well. 137 138 Said developer then verifies that the assert works (using -O0), and commits 139 the code. 140 141 Some other developer then checks out the code and accidentally writes some 142 variant of: 143 ... 144 foo (variable_with_nullptr_value); 145 ... 146 and builds with -O2, and ... the assert doesn't trigger, because it's 147 optimized away by gcc. 148 149 There's no suppported recipe to prevent the assertion from being optimized 150 away (other than: build with -O0, or remove the nonnull attribute). Note 151 that -fno-delete-null-pointer-checks does not help. A patch was submitted 152 to improve gcc documentation to point this out more clearly ( 153 https://gcc.gnu.org/pipermail/gcc-patches/2021-July/576218.html ). The 154 patch also mentions a possible workaround that obfuscates the pointer 155 using: 156 ... 157 void foo (void *ptr) { 158 + asm ("" : "+r"(ptr)); 159 gdb_assert (ptr != nullptr); 160 } 161 ... 162 but that still requires the developer to manually add this in all cases 163 where that's necessary. 164 165 A warning was added to detect the situation: -Wnonnull-compare, which does 166 help in detecting those cases, but each new gcc release may indicate a new 167 batch of locations that needs fixing, which means we've added a maintenance 168 burden. 169 170 We could try to deal with the problem more proactively by introducing a 171 gdb_assert variant like: 172 ... 173 void gdb_assert_non_null (void *ptr) { 174 asm ("" : "+r"(ptr)); 175 gdb_assert (ptr != nullptr); 176 } 177 void foo (void *ptr) { 178 gdb_assert_nonnull (ptr); 179 } 180 ... 181 and make it a coding style to use it everywhere, but again, maintenance 182 burden. 183 184 With all these things considered, for now we go with the solution with the 185 least maintenance burden: disable the attribute, such that we reliably deal 186 with it everywhere. */ 187 #undef ATTRIBUTE_NONNULL 188 #define ATTRIBUTE_NONNULL(m) 189 190 #define ATTRIBUTE_UNUSED_RESULT __attribute__ ((__warn_unused_result__)) 191 #define ATTRIBUTE_USED __attribute__ ((__used__)) 192 193 #include "libiberty.h" 194 #include "pathmax.h" 195 #include "gdb/signals.h" 196 #include "gdb_locale.h" 197 #include "ptid.h" 198 #include "common-types.h" 199 #include "common-utils.h" 200 #include "gdb_assert.h" 201 #include "errors.h" 202 #include "print-utils.h" 203 #include "common-debug.h" 204 #include "cleanups.h" 205 #include "common-exceptions.h" 206 #include "gdbsupport/poison.h" 207 208 /* Pull in gdb::unique_xmalloc_ptr. */ 209 #include "gdbsupport/gdb_unique_ptr.h" 210 211 /* sbrk on macOS is not useful for our purposes, since sbrk(0) always 212 returns the same value. brk/sbrk on macOS is just an emulation 213 that always returns a pointer to a 4MB section reserved for 214 that. */ 215 216 #if defined (HAVE_SBRK) && !__APPLE__ 217 #define HAVE_USEFUL_SBRK 1 218 #endif 219 220 #endif /* COMMON_COMMON_DEFS_H */ 221