List of Changes to the Compiler and Emulator

For more details, see documentation.

IF ANYTHING GOES WRONG: (when adding new features it is easy to accidentally break old ones) Remember that you can get around every problem by including inline assembly code in your C program (between [[ and ]] symbols). If you think something isn't working properly, tell me right away and I'll fix it as soon as I can.

1-12-2004, version 2.198 Added network support to the emulator and library: function sys$getip(int *ip) looks up current IP address, function sys$netsnd(int *destip, void *data, int len) transmits IP packet, function sys$netrcv(int *srcip, void *data, int maxlen) receives IP packet. Full documentation to appear as soon as possible. This system emulates IP, so there are no port numbers, just IP addresses. Every instance of the emulator acts as a separate computer, so even if you are running the emulator in two login shells on the same real computer, each run will have a different emulated IP address. To make this possible, emulated IP addresses are SIX bytes long instead of the traditional four. Programs can communicate in this way over the real internet when you are two real computers in exactly the same way as they communicate over the emulated internet when you are running the emulator twice on the same real computer. 17-3-2004, version 2.178 Added vprintf to the stdio library Created a stdlib library containing only exit Created a stdarg library containing numbargs, va_list, va_start, and va_end Fixed a parsing error, sometimes it couldn't tell the difference between a type-cast and a function call, due to dreadful design of C. Fixed a type-checking error, sometimes it wouldn't allow NULL to be assigned to a pointer, due again to the dreadful design of C. 3-12-2003, version 2.173 Added system call functions that give access to the filesystem. sys$open, sys$close, sys$seek, sys$read, and sys$write. These functions may be used to read or write files in the external host real unix filesystem or in the user's own emulated filesystem. If sys$open is given a filename that begins with '@' it treats it as the name of a real unix file (after removing the @), which it opens, and returns a large integer as a file reference. If the filename does not begin with '@' it is simply passed to sys$iopen, which the user is expected to have defined. sys$iopen should do whatever is needed to open an emulated file, and return a small positive integer as a reference to it. Similarly, sys$close and all the others take a file reference integer as their first parameters; if that integer is large (>=1000) it is assumed to be a reference to a real unix file, and is handled internally. If it is small, the parameters are passed untouched to the corresponding sys$i... system call, which the user is expected to have defined to provide the appropriate functions for emulated files. 1-12-2003, version 2.172 Fixed an error: continue inside a for loop was jumping to the wrong place and not incrementing the controlling variable. 30-11-2003, version 2.171 Added functions for finding the time and date, and for converting dates into convenient formats. See functions sys$daytim, sys$encday, and sys$decday int the Library Documentation. 15-11-2003, version 2.170 Fixed memory allocation problem: large local objects weren't getting all their pages allocated, and that caused access violations in running programs. Changed maximum disc size to 3000 blocks, so you can at least simulate a whole floppy. 4-11-2003, version 2.167 New system call sys$defsys allows programs to define new or redefine existing system calls. New assembler directive ".define name val" allows constants to be declared. 3-11-2003, version 2.166 Added support for dynamic linkage, with the new system function sys$load and the compiler directive #entry. 3-11-2003, up to version 2.164 various error fixes as they turned up, including printfs with mixed chars and ints, initialising a variable with a negative value, some functions "falling through" to the next function instead of returning at the end. Local variables of array, struct, or union type can now be given an initial value. Added system functions and commands for accessing a global symbol table 18-12-2002, version 1.143 C++-style for loops now permitted, e.g. for (int i=3;... The introduced variable is handled correctly, not the microsoft way, i.e. it is purely local to the loop. 18-12-2002, version 1.142 Global structs, unions, and arrays of structs and unions may now be initialised, e.g. struct S { int x; int y; int z; }; S a = { 1, 2, 3 }; S A[] = { {1,2,3}, {4,5,6} }; It is still not possible to initialise local arrays or structs. 18-12-2002, version 1.141 Global arrays may now be initialised, e.g. int A[] = {1,2,3}; curly brackets may NOT be elided for multi-dimensional arrays, they must be supplied in full, e.g. int A[2][2] = {{1,2},{3,4}}; It is still not possible to initialise structs or local arrays. 16-12-2002, version 1.140 Enumerations are now available. 'const' works when used gently. 16-12-2002, version 1.139 The sizeof operator is now available, I had forgotten all about it. Fixed a possible error involving char variables being passed to printf Allowed initialisation to be skipped in a for loop (e.g. for(;1;i+=1) ...) Once a struct has been declared, the type can now be referred to either in the C way: struct <name>, or in the C++ way: <name>. 14-12-2002, version 1.137 Making simpler (but less efficient) use of the stack. Problems caused by having large local variables/arrays when your virtual memory system isn't allocating new pages properly should not occur any more. 13-12-2002, version 1.135 Making safe: if a C program uses a variable that is identical to an opcode recognised by the assembler, a '$' sign is appended to the beginning of its name. This should be undetectable to users except in error messages and when looking at the generated .ass file. 12-12-2002, version 1.133 Repair: strings passed to functions from a struct inside another struct didn't work properly, they do now. Had forgotten the % and %= operators: now added. 11-12-2002 (b), version 1.131 New way to avoid problems until I can fix them: option -i to the cmp command or -ie to the exe command, tells the compiler to try to ignore fatal errors. They are still reported, but the system tries its best to continue. Prototypes and later function definitions are now checked for having the same types. 10-12-2002 (b), version 1.128 Fixed error that I caused last night. \n in strings had stopped working. 10-12-2002 (a), version 1.127 Better handling of automatic type-casts (coercions) for function arguments. 9-12-2002, version 1.126 Fixed an error that made the compiler crash on meeting a declaration of a parameter without a name (which is reasonable inside a prototype). 8-12-2002, version 1.124 Compiler now checks that it is the latest version each time it is run. Added option -v to report current version number. 7-12-2002 Improved behaviour of functions with array parameters, empty bracket [] notation now allowed. 5-12-2002 Fixed error with in-line assembly-language after a #include 3-12-2002 All preprocessor directives are now supported. Error fixed: if two functions were called in the same expression, sometimes the second would overwrite the result of the first; this doesn't happen any more. 1-12-2002 Printf now works completely. typedef is now supported. type-casts are now supported. functions may now return large structs. pre-processor directives #ifdef, #ifndef, #else, #endif are now supported. 25-11-2002 Typecasts are now fully supported. Typedefs are now fully supported. Interrupt functions (see note for 21-11-2002) can now be called in the normal way. 23-11-2002 Repaired a small error which would only exhibit itself if you used the compiler to copy a string backwards. See? I do test things after all, who would have thought of that? 21-11-2002 Compiler first made available. Forgot to mention in class special keyword "interrupt" to allow interrupt handlers to be written in C. (see extras documentation).