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//: Everything this project/binary supports. //: This should give you a sense for what to look forward to in later layers. :(before "End Commandline Parsing") if (argc <= 1 || is_equal(argv[1], "--help")) { //: this is the functionality later layers will provide // currently no automated tests for commandline arg parsing cerr << get(Help, "usage"); return 0; } //: Support for option parsing. //: Options always begin with '--' and are always the first arguments. An //: option will never follow a non-option. char** arg = &argv[1]; while (argc > 1 && starts_with(*arg, "--")) { if (false) ; // no-op branch just so any further additions can consistently always start with 'else' // End Commandline Options(*arg) else cerr << "skipping unknown option " << *arg << '\n'; --argc; ++argv; ++arg; } if (is_equal(argv[1], "help")) { if (argc == 2) { cerr << "help on what?\n"; help_contents(); return 0; } string key(argv[2]); // End Help Special-cases(key) if (contains_key(Help, key)) { cerr << get(Help, key); return 0; } else { cerr << "No help found for '" << key << "'\n"; help_contents(); cerr << "Please check your command for typos.\n"; return 1; } } :(code) void help_contents() { cerr << "Available top-level topics:\n"; cerr << " usage\n"; // End Help Contents } :(before "End Globals") map<string, string> Help; :(before "End Includes") #include <map> using std::map; :(before "End One-time Setup") init_help(); :(code) void init_help() { put(Help, "usage", "bootstrap: the bootstrap translator for SubX.\n" "This program also wraps some miscellaneous useful functionality:\n" " - an x86 emulator: `bootstrap run`\n" " - online help: `bootstrap help`\n" "\n" "== Ways to invoke bootstrap\n" "- See this message:\n" " bootstrap --help\n" "- Convert a textual SubX program into a standard ELF binary that you can\n" " run on your computer:\n" " bootstrap translate input1.subx input2.subx ... -o <output ELF binary>\n" "- Run a SubX binary using SubX itself (for better error messages):\n" " bootstrap run <ELF binary>\n" "- Run all bootstrap's unit tests:\n" " bootstrap test\n" "- Run a single unit test:\n" " bootstrap test <test name>\n" " e.g. bootstrap test test_copy_imm32_to_EAX\n" "\n" "== Debugging aids\n" "- Add '--trace' to any of these commands to save a trace to disk at the end.\n" " This can run out of memory for long-running commands.\n" "- Add '--debug' to emit additional debug information during translation.\n" " 'bootstrap --debug translate' will save metadata to disk that\n" " 'bootstrap --trace run' uses to make traces more informative.\n" "\n" "Options starting with '--' must always come before any other arguments.\n" "\n" "To start learning how to write SubX programs, see Readme.md (particularly\n" "the section on the x86 instruction set) and then run:\n" " bootstrap help\n" ); // End Help Texts } :(code) bool is_equal(const char* s, const char* lit) { size_t len = strlen(lit); if (strlen(s) != len) return false; return strncmp(s, lit, len) == 0; } bool starts_with(const string& s, const string& pat) { string::const_iterator a=s.begin(), b=pat.begin(); for (/*nada*/; a!=s.end() && b!=pat.end(); ++a, ++b) if (*a != *b) return false; return b == pat.end(); } //: I'll throw some style conventions here for want of a better place for them. //: As a rule I hate style guides. Do what you want, that's my motto. But since //: we're dealing with C/C++, the one big thing we want to avoid is undefined //: behavior. If a compiler ever encounters undefined behavior it can make //: your program do anything it wants. //: //: For reference, my checklist of undefined behaviors to watch out for: //: out-of-bounds access //: uninitialized variables //: use after free //: dereferencing invalid pointers: null, a new of size 0, others //: //: casting a large number to a type too small to hold it //: //: integer overflow //: division by zero and other undefined expressions //: left-shift by negative count //: shifting values by more than or equal to the number of bits they contain //: bitwise operations on signed numbers //: //: Converting pointers to types of different alignment requirements //: T* -> void* -> T*: defined //: T* -> U* -> T*: defined if non-function pointers and alignment requirements are same //: function pointers may be cast to other function pointers //: //: Casting a numeric value into a value that can't be represented by the target type (either directly or via static_cast) //: //: To guard against these, some conventions: //: //: 0. Initialize all primitive variables in functions and constructors. //: //: 1. Minimize use of pointers and pointer arithmetic. Avoid 'new' and //: 'delete' as far as possible. Rely on STL to perform memory management to //: avoid use-after-free issues (and memory leaks). //: //: 2. Avoid naked arrays to avoid out-of-bounds access. Never use operator[] //: except with map. Use at() with STL vectors and so on. //: //: 3. Valgrind all the things. //: //: 4. Avoid unsigned numbers. Not strictly an undefined-behavior issue, but //: the extra range doesn't matter, and it's one less confusing category of //: interaction gotchas to worry about. //: //: Corollary: don't use the size() method on containers, since it returns an //: unsigned and that'll cause warnings about mixing signed and unsigned, //: yadda-yadda. Instead use this macro below to perform an unsafe cast to //: signed. We'll just give up immediately if a container's ever too large. //: Basically, Mu is not concerned about this being a little slower than it //: could be. (https://gist.github.com/rygorous/e0f055bfb74e3d5f0af20690759de5a7) //: //: Addendum to corollary: We're going to uniformly use int everywhere, to //: indicate that we're oblivious to number size, and since Clang on 32-bit //: platforms doesn't yet support multiplication over 64-bit integers, and //: since multiplying two integers seems like a more common situation to end //: up in than integer overflow. :(before "End Includes") #define SIZE(X) (assert((X).size() < (1LL<<(sizeof(int)*8-2))), static_cast<int>((X).size())) //: 5. Integer overflow is guarded against at runtime using the -ftrapv flag //: to the compiler, supported by Clang (GCC version only works sometimes: //: http://stackoverflow.com/questions/20851061/how-to-make-gcc-ftrapv-work). :(before "atexit(reset)") initialize_signal_handlers(); // not always necessary, but doesn't hurt //? cerr << INT_MAX+1 << '\n'; // test overflow //? assert(false); // test SIGABRT :(code) // based on https://spin.atomicobject.com/2013/01/13/exceptions-stack-traces-c void initialize_signal_handlers() { struct sigaction action; bzero(&action, sizeof(action)); action.sa_sigaction = dump_and_exit; sigemptyset(&action.sa_mask); sigaction(SIGABRT, &action, NULL); // assert() failure or integer overflow on linux (with -ftrapv) sigaction(SIGILL, &action, NULL); // integer overflow on OS X (with -ftrapv) } void dump_and_exit(int sig, siginfo_t* /*unused*/, void* /*unused*/) { switch (sig) { case SIGABRT: #ifndef __APPLE__ cerr << "SIGABRT: might be an integer overflow if it wasn't an assert() failure\n"; _Exit(1); #endif break; case SIGILL: #ifdef __APPLE__ cerr << "SIGILL: most likely caused by integer overflow\n"; _Exit(1); #endif break; default: break; } } :(before "End Includes") #include <signal.h> //: 6. Map's operator[] being non-const is fucking evil. :(before "Globals") // can't generate prototypes for these // from http://stackoverflow.com/questions/152643/idiomatic-c-for-reading-from-a-const-map template<typename T> typename T::mapped_type& get(T& map, typename T::key_type const& key) { typename T::iterator iter(map.find(key)); if (iter == map.end()) { cerr << "get couldn't find key '" << key << "'\n"; assert(iter != map.end()); } return iter->second; } template<typename T> typename T::mapped_type const& get(const T& map, typename T::key_type const& key) { typename T::const_iterator iter(map.find(key)); if (iter == map.end()) { cerr << "get couldn't find key '" << key << "'\n"; assert(iter != map.end()); } return iter->second; } template<typename T> typename T::mapped_type const& put(T& map, typename T::key_type const& key, typename T::mapped_type const& value) { map[key] = value; return map[key]; } template<typename T> bool contains_key(T& map, typename T::key_type const& key) { return map.find(key) != map.end(); } template<typename T> typename T::mapped_type& get_or_insert(T& map, typename T::key_type const& key) { return map[key]; } template<typename T> typename T::mapped_type const& put_new(T& map, typename T::key_type const& key, typename T::mapped_type const& value) { assert(map.find(key) == map.end()); map[key] = value; return map[key]; } //: The contract: any container that relies on get_or_insert should never call //: contains_key. //: 7. istreams are a royal pain in the arse. You have to be careful about //: what subclass you try to putback into. You have to watch out for the pesky //: failbit and badbit. Just avoid eof() and use this helper instead. :(code) bool has_data(istream& in) { return in && !in.eof(); } :(before "End Includes") #include <assert.h> #include <iostream> using std::istream; using std::ostream; using std::iostream; using std::cin; using std::cout; using std::cerr; #include <iomanip> #include <string.h> #include <string> using std::string; #include <algorithm> using std::min; using std::max;


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