代写CS520留学生、代做C/C++设计、C++编程语言调试、代写program

日期：2019-10-18 11:06

CS520 FALL 2019

PROGRAM 3

DUE DATE: OCT 16, 2019

Description

The goal of this assignment is to write a two-pass assembler for the assembly language for the

vm520 virtual machine.

Your work must be done in the context of our assembler "front-end" and conform to the

interfaces I have defined for your code and our code to utilize to interact. The code base you are

to work within is available in ~cs520/public/program3.

You must implement the following three functions:

? initAssemble: This function will be called once at program start-up to allow you to initialize any

data structures, such as the symbol table.

? assemble: This function is called on both the first pass and the second pass for every line of the

input that contains either a label definition or an instruction (or both). The first parameter to this

function is the label being defined, if there is one. The second parameter contains the opcode and

operands for the instruction, if there is one. The details of how instructions are represented are

contained in the file defs.h.

? betweenPasses: This function is called once, after the first pass completes and before the second

pass begins. Its single parameter is the file pointer (FILE*) where you should write the output, the

object file that will be written during the second pass. This function should return the count of the

number of errors detected during the first pass. Our part of the code will not execute the second

pass if errors were detected during the first pass. The goal for full credit on this assignment is to

detect all errors during the first pass or the call to the betweenPasses function.

Stubs for these three functions are present in assemble.c. All your code for this assignment should be

placed in this single file. Do not edit any of the other distributed files!

Understand that a vm520 object file is not an ASCII file. You will want to use od to examine

output files to be sure they are correct. I recommend using the flag -tx4 to show the file in hex as

a sequence of 32-bit words, since an object file is a sequence of 32-bit words.

Points will be awarded for this assignment in the following manner:

? 50 points: Determining addresses for labels in a correct input file. Have the function

betweenPasses write the defined labels and their addresses to stdout, one label per lane, with the

label name being first on the line, followed by one space and the address printed in decimal. The

labels should be printed in ascending order of label names. You should implement the symbol

table using the hash table you constructed for Lab 5.

? 15 points: Detecting all input errors (except errors concerning the importing or exporting of

symbols), during the first pass or in the betweenPasses function. Call the function error (in

message.c) to report all errors*. This function will ensure a common format for all error messages,

including reporting the line number of the error.

? 25 points: Generating the object file for correct input files.

? 10 points: Properly handling import and export directives, including detecting errors and

generating entries in the insymbol and outsymbol sections of the output file.

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Your program will be graded primarily by testing it for correct functionality. In addition,

however, you may lose points if your program is not properly structured and documented.

Decompose sub-problems appropriately into functions and do incremental testing. Leave your

debugging output in your code, but disabled, when you do your final assignment submission.

You will only submit assemble.c and symtab.c. This, of course, means you should not edit any

of the other distributed files.

*example of a .asm file with errors and the error messages printed by the

assembler