# Theory JVMExceptions

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theory JVMExceptions
imports JVMInstructions
begin

    (*  Title:      HOL/MicroJava/JVM/JVMExceptions.thy
        ID:         $Id: JVMExceptions.thy,v 1.7 2005/06/17 14:13:09 haftmann Exp $
        Author:     Gerwin Klein, Martin Strecker
        Copyright   2001 Technische Universitaet Muenchen
    *)

    header {* \isaheader{Exception handling in the JVM} *}

    theory JVMExceptions imports JVMInstructions begin

    constdefs
      match_exception_entry :: "jvm_prog => cname => p_count => exception_entry => bool"
      "match_exception_entry G cn pc ee ==
                     let (start_pc, end_pc, handler_pc, catch_type) = ee in
                     start_pc <= pc ∧ pc < end_pc ∧ G\<turnstile> cn \<preceq>C catch_type"

    consts
      match_exception_table :: "jvm_prog => cname => p_count => exception_table
                              => p_count option"
    primrec
      "match_exception_table G cn pc []     = None"
      "match_exception_table G cn pc (e#es) = (if match_exception_entry G cn pc e
                                               then Some (fst (snd (snd e)))
                                               else match_exception_table G cn pc es)"

    consts
      ex_table_of :: "jvm_method => exception_table"
    translations
      "ex_table_of m" == "snd (snd (snd m))"

    consts
      find_handler :: "jvm_prog => val option => aheap => frame list => jvm_state"
    primrec
      "find_handler G xcpt hp [] = (xcpt, hp, [])"
      "find_handler G xcpt hp (fr#frs) =
          (case xcpt of
             None => (None, hp, fr#frs)
           | Some xc =>
           let (stk,loc,C,sig,pc) = fr in
           (case match_exception_table G (cname_of hp xc) pc
                  (ex_table_of (snd(snd(the(method (G,C) sig))))) of
              None => find_handler G (Some xc) hp frs
            | Some handler_pc => (None, hp, ([xc], loc, C, sig, handler_pc)#frs)))"

    text {*
      System exceptions are allocated in all heaps:
    *}

    text {*
      Only program counters that are mentioned in the exception table
      can be returned by @{term match_exception_table}:
    *}
    lemma match_exception_table_in_et:
      "match_exception_table G C pc et = Some pc' ==> ∃e ∈ set et. pc' = fst (snd (snd e))"
      by (induct et) (auto split: split_if_asm)

    end

lemma match_exception_table_in_et:

      match_exception_table G C pc et = Some pc'
      ==> ∃e∈set et. pc' = fst (snd (snd e))