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Where to get the grammar
The latest grammar is always located in the java.g file.
(N.B.: Older versions of the grammar, such as java_1_4.g and java_1_5.g are not supported and are no longer functional.). Go to the org.eclipse.jdt.core plugins
directory (eclipse\plugins\org.eclipse.jdt.core where eclipse is the root of your eclipse installation) and open the
grammar directory. Then search for the java.g file inside the
folder grammar. Then copy its contents from:
--main options
%options ACTION, AN=JavaAction.java, GP=java,
....
$end
-- need a carriage return after the $end
into a file called java.g. It is important to add a carriage return at the end of the last line.
You can save this file where you want, we will assume from thereon you saved it in d:\temp\ .
If the end-of-line of the environment of the C compiler used to build jikespg is different from the one used when running the executable, you might end up with an exception at runtime.
Be sure to used consistent end-of-line characters.
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What to do with these files and update the parser class...
Assuming the Jikespg executable (jikespg.exe ) is located in d:\jikespg .
- First in a console, run:
d:
cd \temp
d:\jikespg\jikespg.exe java.g
- You will get an output that looks like this:
IBM Research Jikes Parser Generator Fri Oct 14 09:22:32 2005
%OPTIONS ACTION, AN=JavaAction.java, GP=java,
%OPTIONS FILE-PREFIX=java, ESCAPE=$, PREFIX=TokenName, OUTPUT-SIZE=125 ,
%OPTIONS NOGOTO-DEFAULT, SINGLE-PRODUCTIONS, LALR=1 , TABLE,
%OPTIONS ERROR_MAPS
%OPTIONS first follow
%OPTIONS TRACE=FULL ,
%OPTIONS VERBOSE
%OPTIONS DEFERRED
%OPTIONS NAMES=MAX
%OPTIONS SCOPES
Options in effect:
ACTION ACTFILE-NAME=JavaAction.java BLOCKB=/. BLOCKE=./ BYTE CONFLI
DEFAULT=5 NODEBUG DEFERRED NOEDIT ERROR-MAPS ESCAPE=$
FILE-PREFIX=java FIRST FOLLOW GENERATE-PARSER=JAVA NOGOTO-DEFAULT
HACTFILE-NAME=javahdr.java HBLOCKB=/: HBLOCKE=:/ LALR=1 LIST
MAX-DISTANCE=30 MIN-DISTANCE=3 NAMES=MAXIMUM NONT-CHECK ORMARK=|
OUTPUT-SIZE=125 PREFIX=TokenName READ-REDUCE SCOPES NOSHIFT-DEFAULT
SINGLE-PRODUCTIONS STACK-SIZE=128 STATES SUFFIX= TABLE=SPACE
TRACE=FULL VERBOSE WARNINGS XREF
*** The following Terminals are useless:
const goto
This grammar is LALR(1).
Number of Terminals: 110
Number of Nonterminals: 306
Number of Productions: 693
Number of Single Productions: 232
Number of Items: 2165
Number of Scopes: 132
Number of States: 954
Number of Shift actions: 6057
Number of Goto actions: 7493
Number of Shift/Reduce actions: 593
Number of Goto/Reduce actions: 1041
Number of Reduce actions: 13922
Number of Shift-Reduce conflicts: 0
Number of Reduce-Reduce conflicts: 0
Reallocating storage for SPACE table, adding 2820 entries
Length of base Action Table: 12268
Number of entries in base Action Table: 9488
Percentage of increase: 29.3%
Storage required for base Tables: 24536 Bytes, 24K
Storage required for Rules: 2076 Bytes
Number of unique terminal states: 727
Number of Shift actions saved by merging: 4113
Number of Reduce actions saved by merging: 967
Number of Reduce saved by default: 8997
Length of Terminal Check Table: 7913
Length of Terminal Action Table: 7902
Number of entries in Terminal Action Table: 7222
Percentage of increase: 9.4%
Storage required for Terminal Tables: 23717 Bytes, 24K
Total storage required for Tables: 48253 Bytes, 48K
Actions in Compressed Tables:
Number of Shifts: 2211
Number of Shift/Reduces: 326
Number of Gotos: 7493
Number of Goto/Reduces: 1041
Number of Reduces: 3958
Number of Defaults: 475
Error maps storage:
Storage required for ACTION_SYMBOLS_BASE map: 1908 Bytes
Storage required for ACTION_SYMBOLS_RANGE map: 1709 Bytes
Storage required for NACTION_SYMBOLS_BASE map: 1908 Bytes
Storage required for NACTION_SYMBOLS_RANGE map: 960 Bytes
Storage required for TERMINAL_INDEX map: 220 Bytes
Storage required for NON_TERMINAL_INDEX map: 614 Bytes
Storage required for STRING_BUFFER map: 12004 Bytes
***Warning: Base Check vector contains value > 127. 16-bit words used.
Escaped symbol $eof is an invalid C variable.
Escaped symbol $error is an invalid C variable.
It can be quite different if the output changed since version 1.3 of jikespg. The important part is:
This grammar is LALR(1).
This creates some java source files and information files in the current directory.
java.l |
Information generated by jikespg. Enumarate all the states created for the automaton, etc. |
JavaAction.java |
Contains the method consumeRule(int) of class org.eclipse.jdt.internal.compiler.parser.Parser, which handles all semantic action dispatches. |
javahdr.java |
Used to generate the resources files. |
javadcl.java |
Used to generate the resources files. |
javasym.java |
Contents of the class org.eclipse.jdt.core.compiler.TerminalTokens. |
javadef.java |
Contents of the class org.eclipse.jdt.internal.compiler.parser.ParserBasicInformation. |
javaprs.java |
You don't need this file. Its contents is already inlined in the Parser class. |
Now we need to update the different classes and resource files.
- Copy the contents of the JavaAction.java file into the consumeRule(int) method of the org.eclipse.jdt.internal.compiler.parser.Parser class.
- The class org.eclipse.jdt.internal.compiler.parser.ParserBasicInformation needs to be updated with the content of the file javadef.java. Don't copy the
interface name. Simply copy the field declarations. The actual source of this class will guide you.
- Similarly, update the class org.eclipse.jdt.internal.compiler.parser.TerminalTokens with the contents of the file javasym.java.
- The last step is to update the resource files:
Copy the jdtcore.jar file in d:\temp. Compile this source inside d:\temp. You will have a file UpdateParserFiles.class.
Then run the following command-line:
D:\temp>java -classpath jdtcore.jar:. UpdateParserFiles javadcl.java javahdr.java
Once this done, you will end up with 25 new files inside d:\temp. They are called parser<n>.rsc, with n equals to 1..24 and readableNames.properties.
All these files need to be moved to the org\eclipse\jdt\internal\compiler\parser folder. Now you are ready to execute and test
the new parser.
Warning: If the number of terminals is over 128, then the parser term_check field needs to be converted
to a char[] . Also the generation of the parser resources files needs to be changed to support
an array of char[] .
NOTE: Changing the parser is a risky operation if you miss one of the steps above. The resulting parser can be completely
unpredictable. It can go from crashing to reporting invalid errors. Be sure that you followed all the steps and that all the
files are updated and recompiled before you run it.
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