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). */ 217 extern 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