1 /* Common definitions. 2 3 Copyright (C) 1986-2021 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 #ifndef __STDC_CONSTANT_MACROS 51 #define __STDC_CONSTANT_MACROS 1 52 #endif 53 #ifndef __STDC_LIMIT_MACROS 54 #define __STDC_LIMIT_MACROS 1 55 #endif 56 #ifndef __STDC_FORMAT_MACROS 57 #define __STDC_FORMAT_MACROS 1 58 #endif 59 60 /* Some distros enable _FORTIFY_SOURCE by default, which on occasion 61 has caused build failures with -Wunused-result when a patch is 62 developed on a distro that does not enable _FORTIFY_SOURCE. We 63 enable it here in order to try to catch these problems earlier; 64 plus this seems like a reasonable safety measure. The check for 65 optimization is required because _FORTIFY_SOURCE only works when 66 optimization is enabled. If _FORTIFY_SOURCE is already defined, 67 then we don't do anything. Also, on MinGW, fortify requires 68 linking to -lssp, and to avoid the hassle of checking for 69 that and linking to it statically, we just don't define 70 _FORTIFY_SOURCE there. */ 71 72 #if (!defined _FORTIFY_SOURCE && defined __OPTIMIZE__ && __OPTIMIZE__ > 0 \ 73 && !defined(__MINGW32__)) 74 #define _FORTIFY_SOURCE 2 75 #endif 76 77 /* We don't support Windows versions before XP, so we define 78 _WIN32_WINNT correspondingly to ensure the Windows API headers 79 expose the required symbols. */ 80 #if defined (__MINGW32__) || defined (__CYGWIN__) 81 # ifdef _WIN32_WINNT 82 # if _WIN32_WINNT < 0x0501 83 # undef _WIN32_WINNT 84 # define _WIN32_WINNT 0x0501 85 # endif 86 # else 87 # define _WIN32_WINNT 0x0501 88 # endif 89 #endif /* __MINGW32__ || __CYGWIN__ */ 90 91 #include <stdarg.h> 92 #include <stdio.h> 93 94 /* Include both cstdlib and stdlib.h to ensure we have standard functions 95 defined both in the std:: namespace and in the global namespace. */ 96 #include <cstdlib> 97 #include <stdlib.h> 98 99 #include <stddef.h> 100 #include <stdint.h> 101 #include <string.h> 102 #ifdef HAVE_STRINGS_H 103 #include <strings.h> /* for strcasecmp and strncasecmp */ 104 #endif 105 #include <errno.h> 106 #if HAVE_ALLOCA_H 107 #include <alloca.h> 108 #endif 109 110 #include "ansidecl.h" 111 /* This is defined by ansidecl.h, but we prefer gnulib's version. On 112 MinGW, gnulib might enable __USE_MINGW_ANSI_STDIO, which may or not 113 require use of attribute gnu_printf instead of printf. gnulib 114 checks that at configure time. Since _GL_ATTRIBUTE_FORMAT_PRINTF_STANDARD 115 is compatible with ATTRIBUTE_PRINTF, simply use it. */ 116 #undef ATTRIBUTE_PRINTF 117 #define ATTRIBUTE_PRINTF _GL_ATTRIBUTE_FORMAT_PRINTF_STANDARD 118 119 /* This is defined by ansidecl.h, but we disable the attribute. 120 121 Say a developer starts out with: 122 ... 123 extern void foo (void *ptr) __atttribute__((nonnull (1))); 124 void foo (void *ptr) {} 125 ... 126 with the idea in mind to catch: 127 ... 128 foo (nullptr); 129 ... 130 at compile time with -Werror=nonnull, and then adds: 131 ... 132 void foo (void *ptr) { 133 + gdb_assert (ptr != nullptr); 134 } 135 ... 136 to catch: 137 ... 138 foo (variable_with_nullptr_value); 139 ... 140 at runtime as well. 141 142 Said developer then verifies that the assert works (using -O0), and commits 143 the code. 144 145 Some other developer then checks out the code and accidentally writes some 146 variant of: 147 ... 148 foo (variable_with_nullptr_value); 149 ... 150 and builds with -O2, and ... the assert doesn't trigger, because it's 151 optimized away by gcc. 152 153 There's no suppported recipe to prevent the assertion from being optimized 154 away (other than: build with -O0, or remove the nonnull attribute). Note 155 that -fno-delete-null-pointer-checks does not help. A patch was submitted 156 to improve gcc documentation to point this out more clearly ( 157 https://gcc.gnu.org/pipermail/gcc-patches/2021-July/576218.html ). The 158 patch also mentions a possible workaround that obfuscates the pointer 159 using: 160 ... 161 void foo (void *ptr) { 162 + asm ("" : "+r"(ptr)); 163 gdb_assert (ptr != nullptr); 164 } 165 ... 166 but that still requires the developer to manually add this in all cases 167 where that's necessary. 168 169 A warning was added to detect the situation: -Wnonnull-compare, which does 170 help in detecting those cases, but each new gcc release may indicate a new 171 batch of locations that needs fixing, which means we've added a maintenance 172 burden. 173 174 We could try to deal with the problem more proactively by introducing a 175 gdb_assert variant like: 176 ... 177 void gdb_assert_non_null (void *ptr) { 178 asm ("" : "+r"(ptr)); 179 gdb_assert (ptr != nullptr); 180 } 181 void foo (void *ptr) { 182 gdb_assert_nonnull (ptr); 183 } 184 ... 185 and make it a coding style to use it everywhere, but again, maintenance 186 burden. 187 188 With all these things considered, for now we go with the solution with the 189 least maintenance burden: disable the attribute, such that we reliably deal 190 with it everywhere. */ 191 #undef ATTRIBUTE_NONNULL 192 #define ATTRIBUTE_NONNULL(m) 193 194 #if GCC_VERSION >= 3004 195 #define ATTRIBUTE_UNUSED_RESULT __attribute__ ((__warn_unused_result__)) 196 #else 197 #define ATTRIBUTE_UNUSED_RESULT 198 #endif 199 200 #include "libiberty.h" 201 #include "pathmax.h" 202 #include "gdb/signals.h" 203 #include "gdb_locale.h" 204 #include "ptid.h" 205 #include "common-types.h" 206 #include "common-utils.h" 207 #include "gdb_assert.h" 208 #include "errors.h" 209 #include "print-utils.h" 210 #include "common-debug.h" 211 #include "cleanups.h" 212 #include "common-exceptions.h" 213 #include "gdbsupport/poison.h" 214 215 #define EXTERN_C extern "C" 216 #define EXTERN_C_PUSH extern "C" { 217 #define EXTERN_C_POP } 218 219 /* Pull in gdb::unique_xmalloc_ptr. */ 220 #include "gdbsupport/gdb_unique_ptr.h" 221 222 /* String containing the current directory (what getwd would return). */ 223 extern char *current_directory; 224 225 /* sbrk on macOS is not useful for our purposes, since sbrk(0) always 226 returns the same value. brk/sbrk on macOS is just an emulation 227 that always returns a pointer to a 4MB section reserved for 228 that. */ 229 230 #if defined (HAVE_SBRK) && !__APPLE__ 231 #define HAVE_USEFUL_SBRK 1 232 #endif 233 234 #endif /* COMMON_COMMON_DEFS_H */ 235