Your goal in this step is to generate the parser for the project's grammar. By the end of this step your compiler should be able to take a source file as the input and parse the content of that file returning "Accepted" if the file's content is correct according to the grammar or "Not Accepted" if it is not.
Now the scanner created in the first step will be modified to feed the parser. Instead of printing the tokens, the scanner has to return what token is recognized in each step. The following diagram shows the basic structure of a simple compiler and hightlights the steps that will be completed at the end of this step:
Similar to the scanner case, there are tools that automatically generate parsers based on context-free grammar descriptions. More precisely, there are parser generators for two main classes of context-free grammars: LR(1) and LL(k). Please, refer to the textbook or one of the references at the end of this handout for the theory of LL(k) and LR(k) parsing.
For this project we recommend two main parser generation tools:
At this step you have to create the code for the parser of your compiler. We recommend you to do that using one of the tools described above, although the whole parser could be written manually without the help of any tool.
The following basic steps should be followed:
Testcases can be downloaded here. Note that only ECE 573 students need to handle testcase 22
Java and ANTLR
In Antlr, a parse error throws an exception. So you would have to write an exception handler that catch "ANTLRException" which is the base class of all exceptions in antlr. Also antlr has default error handling that generates error messages and you need to remove those messages. To do that set the option "defaultErrorHandler=false;" in the options section of the parser.
Instead of "options { defaultErrorHandler=false; } " use "@rulecatch { }" for antlrv3
C/C++ and Flex/Bison
When an error occurs in Bison/YACC, the error handler "yyerror" will be invocated. You should customize this handler to print the message and terminate current program.
You will lose 10% of total credit if you failed to follow the following rules.
Assuming the career account name is "sun47"
If Java and ANTLR are used, the directory structure of your project is as follows:
Some_Directory `-- sun47 |-- Makefile |-- build | |-- ... | |-- Files generated by ANTLR from src/*.g | `-- ... |-- classes | |-- ... | |-- *.class files compiled from src/*.java and generated/*.java | |-- Micro.class (The class file of your compiler's main class) | `-- ... |-- lib | `-- antlr.jar `-- src |-- ... |-- Your program's source code (*.java) and ANTLR's input file (*.g) `-- ...
If C/C++ and Flex/Bison are used, the directory structure of your project is as follows:
Some_Directory `-- sun47 |-- Makefile |-- generated | |-- ... | |-- Files generated by Flex/Bison from src/*.l and src/*.y | `-- ... |-- build | |-- ... | |-- *.o files compiled from src/*.c (or src/*.cpp) and generated/*.c (or generated/*.cpp) | |-- micro (The executable file of your compiler) | `-- ... |-- lib (This directory may be empty because library files of Flex/Bison have been installed on ECN machines.) | |-- ... | |-- (Please remember to update the Makefile if you add some other library files here.) | `-- ... `-- src |-- ... |-- Your program's source code (*.h and *.c/*.cpp) and Flex/Bison's input file (*.l and *.y) `-- ...
After ensuring that the directory structure matches the expected structure, turn it in using the turnin command.
Assuming the above directory structure is used
Printing your (and your partner's) ID
Sample Output:
$ cd <Some_Directory>/sun47 $ make group sun47 $
Cleaning all generated files
Sample Output:
$ make clean
After execution, the directory structure will be:
Some_Directory `-- sun47 |-- Makefile |-- lib | `-- ... `-- src `-- ...
Building your compiler
Sample Output:
$ make all
After execution, the class files or executable files of your compiler should be in the sub-directory mentioned above.
Assuming the above directory structure is used
If Java and ANTLR are used, the following command will be run in the directory where Micro.class resides
$ java -cp ../lib/antlr.jar:. Micro <path to test cases>/test.micro Accepted $
If C/C++ and Flex/Bison are used,
$ <build directory>/micro path_to_your_testcases/test.micro Accepted $