C/C++ Interactive Reference Guide

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C Compiler Documentation INTRODUCTION This compiler is the small C compiler written by Ron Cain and published in Dr. Dobb's #45 (May '80). The compiler was modified to include floating point by James R. Van Zandt. The floating point routines themselves were written by Niel Colvin. The companion assembler ZMAC and linker ZLINK were written by Bruce Mallett. This compiler accepts a subset of standard C. It requires a Z-80 processor. It reads C source code and produces Zilog- mnemonic assembly language output, with syntax matching the assembler ZMAC supplied with it. ZMAC produces a relocatable file with the extension .OBJ. One or more such relocatable files can be linkage edited by the companion program ZLINK. The compiler (with source in C), the assembler, and the linker (with sources in assembly language) are hereby placed in the public domain. There are several sample source code files on this disk. For more about the C programming language, see the above issue of Dr. Dobb's or "The C Programming Language" by B. W. Kernighan and D. M. Ritchie, Englewood Cliffs, N.J.: Prentice-Hall, 1978. DATA TYPES The data types are... char c character char *c pointer to character char c[3]; character array int i; 16 bit integer int *i; pointer to integer int i(); function returning integer int i[4]; integer array double d; 48 bit floating point double *d; pointer to double double d(); function returning double double d[5]; array of doubles Storage classes, structures, multidimensional arrays, unions, and more complex types like "int **i" are not included. PRIMARIES array[expression] function(arg1,arg2,...,argn) constant decimal integer decimal floating point (1.0, 2., .3, 340.2e-8) quoted string ("sample string") primed character ('a' or 'Z') local variable global variable Each variable must be declared before it is used. UNARY INTEGER OPERATORS - minus * indirection & address of ++ increment, either prefix or suffix -- decrement, either prefix or suffix BINARY INTEGER OPERATORS + addition - subtraction * multiplication / division % mod, remainder from division | inclusive or ^ exclusive or & logical and == equal != not equal < less than <= less than or equal > greater than >= greater than or equal << left shift >> arithmetic right shift = assignment UNARY DOUBLE OPERATORS - minus BINARY DOUBLE OPERATORS + add - subtract * multiply / divide = assignment Assignment operators are not included. Conversion between floating point and integer is automatic for assignment and for the expression returned by a function. Conversion from integer to floating point is automatic for the arguments of any of the floating point operators. Otherwise, the routines "float(jj)" and "ifix(yy)" (as in FORTRAN) may be used. The arguments of integer-only operators are checked to be sure they are integers. There is no type checking for the actual parameters of function calls. PROGRAM CONTROL if(expression) statement; if(expression) statement; else statement; while(expression) statement; break; continue; return; return expression; ; /* null statement */ {statement;statement; ... statement;} /* compound statement */ not included: for, do while, switch, case, default, goto COMMAND LINES When the compiler is run, it reads one or more C source files and produces one assembly language file. The assembly language files are separately assembled by ZMAC, then are combined into a single executable file by ZLINK. The format of the compiler command line is: cc [options] file [file file...] Each option is a minus sign followed by a letter: -C to include the C source code as comments in the compiler-generated assembly code. -E pause after an error is encountered. -G don't reserve space for any global variables. -M none of these files contains main(). -P produce profile of function calls, and enable walkback trace on calls to err(). Use the -G option if all global variables are being declared in one compilation, but will be used by programs being compiled and assembled separately. (This is a rudimentary form of "extern".) If functions return doubles, they must be declared before use in each compilation. Otherwise, functions are automatically imported and exported. Names of functions and global variables i.e., those declared outside function definitions) are always global as far as the linker are concerned, and may not overlap. The -M option keeps the compiler from producing its standard header (initializing the stack pointer, for example). The header does not include an ORG 100H directive, since ZLINK automatically starts programs at 100H. As a result, forgetting the -M option will lengthen your program by a few bytes but cause no other harm. The profile printout will include only the functions in the first file the linker sees. That's the one that should be compiled with the -P option. If there is a call to err() in IOLIB, a "walkback trace" is printed, which lists all the functions that have been called but which have not yet returned (recursive calls lead to multiple listings). The walkback trace will include all functions compiled with the -P option, whether or not they were in the first .OBJ file. Options and files are separated by spaces, and can be mentioned in any order (even intermixed). Only the file name (optionally preceded by a disk name) should be given. The compiler automatically adds the extension ".C". The output file is given the same name (and is put onto the same disk) as the first input file, but with the extension ".ASM". Each assembly language file is assembled as follows: zmac alpha=alpha If extensions are not specified, as here, ZMAC uses ".ASM" for its input file and ".OBJ" for its output file. The object files are linked as follows: zlink alpha,alpha=alpha,beta,iolib,float,printf The first name is for the output file. By default, it is given the extension ".COM". The second name is for the map file (default extension ".MAP) which gives the values of all the global symbols. ZLINK will always tell you how many global symbols were undefined, but won't tell you what the undefined symbols were unless you ask for a map file. All the names to the right of the '=' are input files, with the default extension ".OBJ". The first input file must have been compiled WITHOUT the -M option. Ordinarily, it will be the one with main(). The other files can be mentioned in any order. EMBEDDED COMPILER COMMANDS #define name string "name" is replaced by "string" hereafter. #include filename compiler gets source code from another file (can't be nested) #asm ... ... #endasm code between these is passed directly to the assembler. LIBRARY FILES Seven library files are included: IOLIB.C Basic input/output and integer math routines IOLIB.ASM (required by ALL programs). IOLIB.H / FLOAT.C Floating point math routines. FLOAT.OBJ / FLOAT.H / TRANSCEN.OBJ Trancendental routines. TRANSCEN.H / PRINTF1.C Output routine printf(), integer only. PRINTF1.OBJ / PRINTF1.H / PRINTF2.C Output routine printf(), PRINTF2.OBJ integer & floating point PRINTF2.H / PROFILE.ASM Prints profile (number of calls to each PROFILE.OBJ function) after program finishes, and enables PROFILE.H walkback trace in case of error (calls to err(), in IOLIB). ARGS.C I/O redirection and command line parsing. ARGS.OBJ / ARGS.H / These are related as follows: IOLIB / | \ \ PRINTF1 | \ ARGS PROFILE \ FLOAT / \ PRINTF2 TRANSCEN That is, PRINTF2 requires both FLOAT and IOLIB. PRINTF1 or PROFILE require only IOLIB. TRANSCEN requires both FLOAT and IOLIB. In each case, the .C file was compiled and assembled to give the corresponding .OBJ file, and the .H file declares (for the assembler, and if necessary for the compiler as well) the exported symbols. Each library to be used must be mentioned twice: once to the compiler (either in an #include statement in the source code or in a reply to the "input file" question), and again to the linker (either in the command line or in a reply to the linker prompt). For example, if floating point operations are needed, the source file should contain: #include iolib.h #include float.h double x; ... (rest of source code) Compilation, assembly, and linking would consist of: A>cc alpha A>zmac alpha=alpha A>zlink alpha=alpha,iolib,float For details on these libraries, see IOLIB.DOC, FLOAT.DOC, TRANSCEN.DOC, PRINTF.DOC, PROFILE.DOC, and ARGS.DOC. SAMPLE COMPILATION C>cc test * * * Small-C V1.2 * * * By Ron Cain and James Van Zandt 29 July 1984 TEST.C <file names echoed> #include iolib.h <included files echoed> #end include #include float.h #end include #include printf2.h #end include #include args.h #end include #include transcen.h #end include ====== main() <function names echoed> ====== out() ====== alpha() ====== beta() ====== gamma() ====== putnum() ====== outf() There were 0 errors in compilation. C>zmac test=test SSD RELOCATING (AND EVENTUALLY MACRO) Z80 ASSEMBLER VER 1.07 0 ERRORS C>zlink test,test=test,a:args,iolib,float,printf2,a:transcen SSD LINKAGE EDITOR VERSION 1.4 0 UNDEFINED SYMBOL(S). C> SAMPLE COMPILER COMPILATION C>cc c80v C>zmac c80v3=c80v <pick a different name> C>zlink c80v3,c80v3=c80v3,iolib,float <link it> The assembly files total about 190K. The object files total about 65K, and the temporary file produced by the linker is about 80K. Compilation requires about 43K of RAM, divided as follows: 34K code & data, 8K heap (mostly symbol table), and 1K stack. PERFORMANCE The program test.c on this disk (with 142 lines and 3200 bytes) was compiled in 47.8 sec on a 4 MHz Z-80, for a compilation speed of approximately 3 lines/sec, or 67 bytes/sec. Of this time, approximately 7 seconds was spent reading in the 43136 bytes of compiler code. The following floating point benchmark (from Dr. Dobb's Journal, Mar 84) finished in 489 seconds on a 4 MHz Z-80, with the result 2500.00469: #include iolib.h #include float.h #include transcen.h #include printf2.h int i; double a; main() { a=1.; i=1; printf("starting\n"); while(i++<2500) {a=tan(atan(exp(ln(sqrt(a*a)))))+1.;} printf("Result is %20.12f ",a); } INTERNAL DOCUMENTATION This is a recursive descent, one pass compiler producing assembly language. The two major changes that have been made to speed it up relative to Ron Cain's original compiler are a hash coded symbol table and 1K disk buffers. Global symbols defined in a C program are prefixed by 'Q' so they do not conflict with any global symbols in libraries. A compiled program has the following layout... 100H to _end-1 program & data _end to *heaptop heap *heaptop to *SP-1 unused *SP to *(0006) stack The symbol _end is defined by ZLINK at link time, and points to the first byte above program and data. The variable heaptop (initialized to _end) always points to the first byte above the heap. The stack pointer register SP is initialized to the first location above user memory (pointed to by the word at 0006). The variable names _end and heaptop are visible only to assembly language programs, since they do not begin with Qs. Assembly language programs can be called by C programs. The C program will evaluate each of its arguments (left to right), push it onto the stack, then call the named program. Therefore, the assembly language program should expect that the top word on the stack is the return address, the next word is the last argument, etc. If the function is to return an integer or character value, it should be left in the HL register. Double values should be left in the 6 byte area starting at FA. WARNINGS In addition to the limitations mentioned above, the user should be aware of the following... In declaring a function returning a double, you have to use two lines... double frodo(); frodo(x,y,z) int x; double y,z; You can't combine them, as in standard C... double frodo(x,y,z) ... /* not accepted */ It addition, the declaration "double frodo();" must appear before any use of the function, or the compiler will assume while generating the calling code that the function returns an integer. The floating point routines in the FLOAT library (though none of the code produced by the compiler) use several of the undocumented Z-80 op codes, so they may not work on some processors. FLOAT also uses the alternate register set. The floating point routines do not meet the proposed IEEE standard. POTENTIAL IMPROVEMENTS Adding the features noted above as "not included". The compiler could probably be made faster by tokenizing the input stream, so parsing would not involve string comparisons. It could be made smaller by moving the error messages to a disk file, to be consulted at need. Implementing storage class specifiers could make compiled programs (and the compiler itself) smaller and faster, since variables local to a function that is not called recursively could be declared "static". Static variables can be accessed much more readily than "auto" variables (those on the stack).