Why is it that the code below behaves differently in Java 1.6 and 1.7 -


the code below

public class test16jit {   public static void main(string[] s) {       int max = integer.max_value;       int = 0;       long li = 0;       while (i >= 0) {           i++;           li++;           if (i > max) {               system.out.println("i : " + i);               system.out.println("max : " + max);               system.out.println("woo!! went wrong");           }       }       system.out.println("value of i: " + i);       system.out.println("total # of iterations: " + li);         } }

outputs below in java 1.7x

value of i: -2147483648 total # of iterations: 2147483648

outputs below in java 1.6x

i : 2147483636 max : 2147483647 woo!! went wrong value of i: -2147483648 total # of iterations: 2147483648

is there reason behavior?

also if change 

int max = integer.max_value; -> final int max = integer.max_value;

it behaves same in 1.6x , 1.7x

it seems 1 of many examples of family of errors related 1 caused jit compilation (i picked 1 due similarity of code, feel free explore others - quite interesting!):

http://bugs.java.com/view_bug.do?bug_id=6196102

evaluation

problem canonicalization of loop exit test in preparation loop transformation.

do while (++i <= limit)

becomes

do while (++i < limit+1)

this isn't correct when limit maxint.

some issues fixed in 1.7, explain results.


Comments

Post a Comment

Popular posts from this blog

jOOQ update returning clause with Oracle -

according http://www.jooq.org/doc/3.8/manual/sql-building/sql-statements/update-statement/ jooq doesn't support returning clause in update statements databases except firebird , postgres. does know, still correct oracle jooq? according oracle's documentation, oracle db supports returning clase delete, insert, or update statements. incorrect manual you're right - manual wrong , should fixed: https://github.com/jooq/jooq/issues/5470 single row update returning jooq 3.8 added support single row update .. returning statements. internally, uses callablestatement , pl/sql block of form: begin update "my_table" set "my_table"."column" = 'xyz' "my_table"."id" = 1 returning "my_table"."id", "my_table"."column" ?, ?; ? := sql%rowcount; end; the relevant issue is: https://github.com/jooq/jooq/issues/5190 multi row update returning a...
Read more

java - Warning equals/hashCode on @Data annotation lombok with inheritance -

i have entity inherits other. on other hand, i'm using lombok project reduce boilerplate code, put @data annotation. annotation @data inheritance produces next warning: generating equals/hashcode implementation without call superclass, though class not extend java.lang.object. if intentional, add '@equalsandhashcode(callsuper=false)' type. is advisable add annotation @equalsandhashcode (callsuper = true) or @equalsandhashcode (callsuper = false) ? if not added, 1 callsuper=false or callsuper=true ? the default value false . 1 if don't specify , ignore warning. yes, recommended add @equalsandhashcode annotation on @data annotated classes extend else object. cannot tell if need true or false , depends on class hierarchy, , need examined on case-by-case basis. however, project or package, can configure in lombok.config call super methods if not direct subclass of object. lombok.equalsandhashcode.callsuper = call for configuration system ...
Read more

java - BasicPathUsageException: Cannot join to attribute of basic type -

i using java 8 jpa (hibernate 5.2.1). have clause works perfectly, until introduce clause make use foreign key table values too. i getting following error: basicpathusageexception: cannot join attribute of basic type i think problem related fact have join table, , not sure how create join using join table. employee - employee_category - category model (employee.java): @manytomany(cascade = cascadetype.all, fetch=fetchtype.eager) @jointable ( name="employee_category", joincolumns={ @joincolumn(name="emp_id", referencedcolumnname="id") }, inversejoincolumns={ @joincolumn(name="cat_id", referencedcolumnname="id") } ) private set<category> categories; model (category.java): @id private string id; jpa when introduce following code, fails error above (i think problem new piece of code): join<t, category> category = from.join("id"); predicates.add(criteriabuilder.like(category....
Read more