053continuation.cc - mu - Soul of a tiny new machine. More thorough tests → More comprehensible and rewrite-friendly software → More resilient society.

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generated by cgit-pink 1.4.1-2-gfad0 (git 2.36.2.497.gbbea4dcf42) at 2024-06-28 00:44:12 +0000

="ni">"\n" 67 "== Ways to invoke bootstrap\n" 68 "- See this message:\n" 69 " bootstrap --help\n" 70 "- Convert a textual SubX program into a standard ELF binary that you can\n" 71 " <a href='011run.cc.html#L82'>run</a> on your computer:\n" 72 " bootstrap translate input1.subx input2.subx ... -o <output ELF binary>\n" 73 "- Run a SubX binary using SubX itself (for better error messages):\n" 74 " bootstrap <a href='011run.cc.html#L82'>run</a> <ELF binary>\n" 75 "- Run all bootstrap's unit tests:\n" 76 " bootstrap test\n" 77 "- Run a single unit test:\n" 78 " bootstrap test <test name>\n" 79 " e.g. bootstrap test test_copy_imm32_to_EAX\n" 80 "\n" 81 "== Debugging aids\n" 82 "- Add '--trace' to any of these commands to save a <a href='003trace.cc.html#L96'>trace</a> to disk at the end.\n" 83 " This can <a href='011run.cc.html#L82'>run</a> out of memory for long-running commands.\n" 84 "- Add '--debug' to emit additional debug information during translation.\n" 85 " 'bootstrap --debug translate' will save metadata to disk that\n" 86 " 'bootstrap --trace run' uses to make traces more informative.\n" 87 "\n" 88 "Options starting with '--' must always come before any other arguments.\n" 89 "\n" 90 "To start learning how to write SubX programs, see Readme.md (particularly\n" 91 "the section on the x86 instruction set) and then <a href='011run.cc.html#L82'>run</a>:\n" 92 " bootstrap help\n" 93 ); 94 // End Help Texts 95 } 96 97 :(code) 98 bool <a href='001help.cc.html#L98'>is_equal</a>(char* s, const char* lit) { 99 return strncmp(s, lit, strlen(lit)) == 0; 100 } 101 102 bool <a href='001help.cc.html#L102'>starts_with</a>(const string& s, const string& pat) { 103 string::const_iterator a=s.begin(), b=pat.begin(); 104 for (/*nada*/; a!=s.end() && b!=pat.end(); ++a, ++b) 105 if (*a != *b) return false; 106 return b == pat.end(); 107 } 108 109 //: I'll throw some style conventions here for want of a better place for them. 110 //: As a rule I hate style guides. Do what you want, that's my motto. But since 111 //: we're dealing with C/C++, the one big thing we want to avoid is undefined 112 //: behavior. If a compiler ever encounters undefined behavior it can make 113 //: your program do anything it wants. 114 //: 115 //: For reference, my checklist of undefined behaviors to watch out for: 116 //: out-of-bounds access 117 //: uninitialized variables 118 //: use after free 119 //: dereferencing invalid pointers: null, a new of size 0, others 120 //: 121 //: casting a large number to a type too small to hold it 122 //: 123 //: integer overflow 124 //: division by zero and other undefined expressions 125 //: left-shift by negative count 126 //: shifting values by more than or equal to the number of bits they contain 127 //: bitwise operations on signed numbers 128 //: 129 //: Converting pointers to types of different alignment requirements 130 //: T* -> void* -> T*: defined 131 //: T* -> U* -> T*: defined if non-function pointers and alignment requirements are same 132 //: function pointers may be cast to other function pointers 133 //: 134 //: Casting a numeric value into a value that can't be represented by the target type (either directly or via static_cast) 135 //: 136 //: To guard against these, some conventions: 137 //: 138 //: 0. Initialize all primitive variables in functions and constructors. 139 //: 140 //: 1. Minimize use of pointers and pointer arithmetic. Avoid 'new' and 141 //: 'delete' as far as possible. Rely on STL to perform memory management to 142 //: avoid use-after-free issues (and memory leaks). 143 //: 144 //: 2. Avoid naked arrays to avoid out-of-bounds access. Never use operator[] 145 //: except with map. Use at() with STL vectors and so on. 146 //: 147 //: 3. Valgrind all the things. 148 //: 149 //: 4. Avoid unsigned numbers. Not strictly an undefined-behavior issue, but 150 //: the extra range doesn't matter, and it's one less confusing category of 151 //: interaction gotchas to worry about. 152 //: 153 //: Corollary: don't use the size() method on containers, since it returns an 154 //: unsigned and that'll cause warnings about mixing signed and unsigned, 155 //: yadda-yadda. Instead use this macro below to perform an unsafe cast to 156 //: signed. We'll just give up immediately if a container's ever too large. 157 //: Basically, Mu is not concerned about this being a little slower than it 158 //: could be. (<a href="https://gist.github.com/rygorous/e0f055bfb74e3d5f0af20690759de5a7">https://gist.github.com/rygorous/e0f055bfb74e3d5f0af20690759de5a7</a>) 159 //: 160 //: Addendum to corollary: We're going to uniformly use int everywhere, to 161 //: indicate that we're oblivious to number size, and since Clang on 32-bit 162 //: platforms doesn't yet support multiplication over 64-bit integers, and 163 //: since multiplying two integers seems like a more common situation to end 164 //: up in than integer overflow. 165 :(before "End Includes") 166 #define SIZE(X) (assert((X).size() < (1LL<<(sizeof(int)*8-2))), static_cast<int>((X).size())) 167 168 //: 5. Integer overflow is guarded against at runtime using the -ftrapv flag 169 //: to the compiler, supported by Clang (GCC version only works sometimes: 170 //: <a href="http://stackoverflow.com/questions/20851061/how-to-make-gcc-ftrapv-work">http://stackoverflow.com/questions/20851061/how-to-make-gcc-ftrapv-work</a>). 171 :(before "atexit(<a href='000organization.cc.html#L150'>reset</a>)") 172 <a href='001help.cc.html#L177'>initialize_signal_handlers</a>(); // not always necessary, but doesn't hurt 173 //? cerr << INT_MAX+1 << '\n'; // test overflow 174 //? assert(false); // test SIGABRT 175 :(code) 176 // based on <a href="https://spin.atomicobject.com/2013/01/13/exceptions-stack-traces-c">https://spin.atomicobject.com/2013/01/13/exceptions-stack-traces-c</a> 177 void <a href='001help.cc.html#L177'>initialize_signal_handlers</a>() { 178 struct sigaction action; 179 bzero(&action, sizeof(action)); 180 action.sa_sigaction = <a href='001help.cc.html#L185'>dump_and_exit</a>; 181 sigemptyset(&action.sa_mask); 182 sigaction(SIGABRT, &action, NULL); // assert() failure or integer overflow on linux (with -ftrapv) 183 sigaction(SIGILL, &action, NULL); // integer overflow on OS X (with -ftrapv) 184 } 185 void <a href='001help.cc.html#L185'>dump_and_exit</a>(int sig, siginfo_t* /*unused*/, void* /*unused*/) { 186 switch (sig) { 187 case SIGABRT: 188 #ifndef __APPLE__ 189 cerr << "SIGABRT: might be an integer overflow if it wasn't an assert() failure\n"; 190 _Exit(1); 191 #endif 192 break; 193 case SIGILL: 194 #ifdef __APPLE__ 195 cerr << "SIGILL: most likely caused by integer overflow\n"; 196 _Exit(1); 197 #endif 198 break; 199 default: 200 break; 201 } 202 } 203 :(before "End Includes") 204 #include <signal.h> 205 206 //: 6. Map's operator[] being non-const is fucking evil. 207 :(before "Globals") // can't generate prototypes for these 208 // from <a href="http://stackoverflow.com/questions/152643/idiomatic-c-for-reading-from-a-const-map">http://stackoverflow.com/questions/152643/idiomatic-c-for-reading-from-a-const-map</a> 209 template<typename T> typename T::mapped_type& get(T& map, typename T::key_type const& key) { 210 typename T::iterator iter(map.find(key)); 211 if (iter == map.end()) { 212 cerr << "get couldn't find key '" << key << "'\n"; 213 assert(iter != map.end()); 214 } 215 return iter->second; 216 } 217 template<typename T> typename T::mapped_type const& get(const T& map, typename T::key_type const& key) { 218 typename T::const_iterator iter(map.find(key)); 219 if (iter == map.end()) { 220 cerr << "get couldn't find key '" << key << "'\n"; 221 assert(iter != map.end()); 222 } 223 return iter->second; 224 } 225 template<typename T> typename T::mapped_type const& <a href='001help.cc.html#L225'>put</a>(T& map, typename T::key_type const& key, typename T::mapped_type const& value) { 226 map[key] = value; 227 return map[key]; 228 } 229 template<typename T> bool <a href='001help.cc.html#L229'>contains_key</a>(T& map, typename T::key_type const& key) { 230 return map.find(key) != map.end(); 231 } 232 template<typename T> typename T::mapped_type& <a href='001help.cc.html#L232'>get_or_insert</a>(T& map, typename T::key_type const& key) { 233 return map[key]; 234 } 235 template<typename T> typename T::mapped_type const& <a href='001help.cc.html#L235'>put_new</a>(T& map, typename T::key_type const& key, typename T::mapped_type const& value) { 236 assert(map.find(key) == map.end()); 237 map[key] = value; 238 return map[key]; 239 } 240 //: The contract: any container that relies on get_or_insert should never call 241 //: contains_key. 242 243 //: 7. istreams are a royal pain in the arse. You have to be careful about 244 //: what subclass you try to putback into. You have to watch out for the pesky 245 //: failbit and badbit. Just avoid eof() and use this helper instead. 246 :(code) 247 bool <a href='001help.cc.html#L247'>has_data</a>(istream& in) { 248 return in && !in.eof(); 249 } 250 251 :(before "End Includes") 252 #include <assert.h> 253 254 #include <iostream> 255 using std::istream; 256 using std::ostream; 257 using std::iostream; 258 using std::cin; 259 using std::cout; 260 using std::cerr; 261 #include <iomanip> 262 263 #include <string.h> 264 #include <string> 265 using std::string; 266 267 #include <algorithm> 268 using std::min; 269 using std::max; </pre> </body> </html>